-------
Figure 30
COEFFICIENT OF VARIATION AS A FUNCTION OF SULFATE CONCENTRATION
WITH THE DIONEX ION CHROMATOGRAPH (Range Ityimho)
10
*•*
d
o
CO
c
Q>
M-l
0)
O
O
0
40
8 0 120 160
Expected Concentration tyig SOT/20ml)
200
240
-------
VIII. INTERFERENCE EFFECTS
A. Introduction
Previous AIHL studies have included effects of potential interferents
singly, in pairs and quartets in relation to a series of sulfate
1 2
methods. ' Interferents selected for study and their concentrations
were based, in part, on measurements of atmospheric participates.
The present study includes four potential interferents: phosphate,
colloidal clay (to simulate turbid extracts), water-soluble organics
contributing absorbance in ^00-500 nm range as isolated from Cali-
fornia atmospheric samples, and bicarbonate. The isolation of the
organics is described in Appendix G.
The scheme for the study is shown in Table U5. Phosphate was studied
only with MTB procedures based on previous work indicating significant
interference and high phosphate levels (ca. 2000 yg/8 x 10" filter)
2
in early batches of Gelman "EPA Grade" filters. As with clay,
concentrations were decreased tenfold for the Colovos MTB. The levels
of colloidal clay used were chosen based on prior evaluation of the
turbidity of atmospheric extracts prepared from 3A x 8" strips from
2
2U-hour hi-vol filter samples collected in St. Louis. The maximum
turbidity observed was equivalent to that of a colloidal suspension
of 1*0 yg/ml bentonite clay or 25 yg/ml kaolinite. For analysis based
on use of lA of a 8 x 10" filter the maximum turbidity expected was
calculated as 65 yg/ml kaolinite. This calculation was used to set
concentrations for the Midwest MTB and Method 75- Because of smaller
samples anticipated with use of the Colovos method in the 0-10 yg/ml
sulfate range, concentrations of clay were decreased by a factor of 10.
- 115 -
-------
Table ^5
Sulfate and Interferent Levels for Interference Studies
Method.
MR I MTB
(0-100 (ug/ml S04=)
Colovos MTB
(0-10 jug/ml S04~)
(S04~) (P04=)
Ug/ml jug/ml
10 10, 5, 2.5, 1-25
35 10, 5, 2.5, 1.25
60 10, 5, 2.5, 1.25
1.5 l.O, 0.5, 0.25, 0.125
5 1.0, 0.5, 0.25, 0.125
8.5 l.O, 0.5, 0.25, 0.125
Colloidal
clay
(iug/ml)
75, 50, 25, 10
75, 50, 25, 10
75, 50, 25, 10
7.5, 5, 2.5, l.O
7-5, 5, 2.5, l.O
7.5, 5, 2.5, l.O
Organics
from Atmos. Ext-
Abs./cm at ^00 nm
.1, .05, .025, .0125
.1, .05, .025, .0125
.1, .05, .025, .0125
.05, .025, .0125, .006
.05, .025, .0125, .006
.05, .025, .0125, .006
(HC03~)
Method 75
a\
i
10
35
60
75, 50, 25, 10
75, 50, 25, 10
75, 50, 25, 10
.1, .05, .025, .0125
.1, .05, .025, .0125
.1, .05, .025, .0125
30,15,7.5,3.8
30,15,7.5,3.8
30,15,7.5,3.8
a. Using kaolinite clay
b. Extracted by the procedure given in Appendix G.
-------
Similarly, based on the previous study the maximum level of organics
expected, as measured by absorbance at UOO nm for extraction of one
quarter filter is A = 0.07. The bicarbonate concentrations selected
were based on preliminary results which showed a slight positive
interference with 10 yg/ml bicarbonate for one version of the BaSO^
turbidimetric method.
B. Method 75
The results of the interference study with Method 75 using third order
regression are shown in Table U6. While analyses are performed on
20 ml samples, results have been expressed per ml of solution for
ease in comparison with other methods. Colloidal clay showed the
largest interference. Its interference was clearly observable at all
sulfate levels but was largest at low sulfate. Increasing concen-
trations of clay produced a decreasing observed sulfate value.
However, at low levels of sulfate and high clay concentrations results
became erratic.
Organics produced a measurable (up to 17$) negative interference at
the lowest sulfate level. At higher sulfate values no interference
was observable. Bicarbonate did not interfere at any sulfate level.
C. Midwest Research Ihstitute-MTB Method
Results with the MRI-MTB method are shown in Table ^7. At 10 yg/ml
sulfate, results are shown without added interferent because, using
linear regression, the method yields low values at this level. At
10 ug/ml sulfate no interferences are observable in part because of
- 117 -
-------
Table U6
Interference Effect vith the AIHL Method 75 (yg/ml Observed Sulfate)'
Sulfate Level
UK/ml
Interferent Level b
Inter ferent
Colloidal clay
Organics
bicarbonate (HCOs"")
10
A
8.8
1.6
9.4
0.9
10.2
0.2
B C
5.2 1.6°
2.3
9.9 9.4
0.3 0.3
10.1 10.0
0.7 0.6
D
2.9d
1.0
8.3
0.3
10.4
0.3
35
A
35.3
0.5
35.4
1.9
37.0
0.3
B
33.2
0.3
35.8
0-5
36.1
0.2
C
31.2
0.2
35.2
0.7
36.5
0.5
D
30.0
0.6
35.2
0.4
36.0
0.6
60
A
58.3
0.9
60.0
0.7
60.0
0.3
B
56.2
1.2
60.5
0.5
59.5
0.9
C
53.0
0.7
59.0
1.1
60.2
0.8
D
50.7
0.7
59.1
2.4
60.0
0.6
I
H
H
co
I
a. Mean of three determinations, third order regression, vith +_ 1 o values shown below mean.
b. Interferent concentrations: .
A a 0 D
Colloidal clay (yg/ml)
Organics (Abs/cm at UOO run)
bicarbonate (ug/ml)
10 25 50 75
0.0125 0.025 0.05 0.1
3.8 7.5 15 30
c. Single value. Two trials yielded negative results.
d. Mean of two results. One value yielded negative results.
-------
Table
Interference Effects with the MRI-MTB Method
Sulfate Level
UK/ml
Interferent Level ^ Oc
Interf erent :
Colloidal clay ®'-?
n • 8-°
Organics 2
Phosphate
A
10.1
1-7
9.7
0.8
6.5
0.5
B
7.8
0.7
7.3
1.0
6.7
0.8
10
C
7.6
0.7
7.3
0.7
7.7
o.4
D A
7.7 35.6
0.6 0.7
7.3 33.5
0.7 0.6
9.2 36.0
1.5 0.3
B
35.7
0.6
35.4
0.5
35.7
0.4
35
C
33.1
4.2
35.9
0.4
36.4
0.4
D
36.7
0.7
36.2
0.3
36.1
0.4
60
A
60.7
1.3
61.2
1.2
61.8
1.3
B
62.2
0.4
61.9
0.5
63.0
0.5
C
62.7
1.0
62.5
1.3
62.8
0.9
D
63.2
0.5
63.8
1.1
63.1
1.9
I
H
a. Mean of three determinations, third order regression, with +_ 1 a values shown below mean.
ID. Interferent concentrations:
B
Colloidal clay (yg/ml)
Organics (abs/cm at 400 nm)
Phosphate (Mg/ml)
10
0.0125
1.25
25
0.025
2.5
50
0.05
5
75
0.1
10
c. Deviations from true sulfate level reflect poor fit of linear regression equation at this level
-------
the relatively poor precision of the method observed at this
concentration. At 35 and 60 yg/ml sulfate, colloidal clay and
organics exhibit small positive interference. Interference from
phosphate at <_ 10 yg/ml was not clearly established at any of the
three sulfate levels.
D. Colovos MTB Method (0-10 yg/ml range)
Results with the Colovos MTB method are given in Table U8. At
1.5 yg/ml sulfate only organics exhibit a measurable interference.
The positive interference by yellow organics is more easily seen at
5 and 8.5 yg/ml sulfate. Colloidal clay shows evidence of positive
interference at 5 and 8.5 yg/ml sulfate. No clear evidence of
phosphate interference is seen. As expected, these results are
similar to those observed with the MRI-MTB method in the 0-100 yg/ml.
E. Dionex Ion Chromatograph
1. Introduction
Results obtained using EPA audit strips containing both sulfate
and nitrate, the evaluation of relative accuracy, and the inter-
method comparison results in Section IX suggest that the ion
chromatograph sulfate results may be up to 5$ high. A potential
source of some of this error is the slight overlap of the nitrate
and sulfate peaks observed during the current program. In
principle, the mutual influence of such ions could be eliminated
by employing standards prepared with both sulfate and nitrate at
about the same levels as in the samples. However, because of the
variability in the sulfate to nitrate ratio in atmospheric samples,
this approach appears impractical.
- 120 -
-------
Table U8
Interference Effect with the Colovos MTB Method (yg/ml Observed Sulfate)
Sulfate Level
yg/ml
Interferent Level
Interferent
Colloidal clay
Organic s
Phosphate (P0i,.~)
A
1.67
0.16
1.57
0.18
1.31
0.06
1.
B
1.1*6
0.02
1.1*6
0.06
1.68
5C
c
1.1*7
0.00
1.57
0.03
1.23
0.01
D
1.1*6
0.02
1.83
o.o>*
1.23
0.01
5.0 8.5
ABCD ABCD
5.00 5.05 5.11 5.19 8.69 8 .-91 9.17 9.05
0.23 0.12 0.06 0.05 0.21* 0.15 0.07 0.08
5.10 5.17 5-26 5-59 8.72 8.97 9-22 9.M-
0.15 0.13 0.03 0.03 0.35 0.09 0.03 0.04
5.03 U.98 5.70 5.05 9-51 8.91 8.8U 9.03
0.02 0.11 0.60 O.Qi* 0.91* 0.05 0.07 0.09
ro
H
a. Except as noted, mean of three determinations, linear regression with ^ 1 a values
shown below mean.
b. Interferent concentrations:
Colloidal clay (yg/ml)
Organics (Abs/cm at 1*00 nm,
Phosphate (yg/ml)
B
D
1.0
0.006
0.125
2.0
0.0125
0.25
5.0
0.025
0.50
7.5
0.05
1.0
c. Mean of two results. One set of results yielded values which were too high because of a
poor fit of the working curve at 1 yg/ml using linear regression.
-------
The current study employed a 3 x 500 mm anion separator column
which was close to the end of its useful life. Accordingly,
the extent of nitrate interference with this column was evaluated
together with that for a new column. While no evaluation of the
interference of sulfate in nitrate determination was made, similar
results would be expected.
2. Results
Standards containing from 20 to 80 yg/ml sulfate and U to 80 yg/ml
nitrate were analyzed and compared to results for sulfate standards
of equal concentrations without nitrate. The latter were run in
succession with the mixed standard of equal sulfate level. The
interference was judged by a change in the peak height for sulfate
compared to that for the sulfate standard. Since peak heights are
used for constructing working curves (which have negligible inter-
cepts) the percentage change in peak heights equals the per-
centage change in observed concentration.
Results are given in Table k$ for both the old and new anion
separator column. Flow rates were varied from 2.5 to 3.3 ml/min
and the temperature from 23 to 35°C. Retention times for sulfate
and nitrate were markedly lower for the old column. However, the
retention time difference between sulfate and nitrate had decreased
by only 19 seconds (ll$). At 20 yg/ml, sulfate and nitrate
interference was not reliably measured. Results at Uo and 80 yg/ml
sulfate with equal concentration (by weight) of nitrate, showed
increased sulfate signal with both the old and new columns. For
- 122 -
-------
Tattle h9
Interference of Nitrate in Sulfate Determination with the Dionex Ion Chromatograph
H
ro
Eluent Flow Rate
(ml/min)
3.26
3.26
2.50
,26
.26
,26
,26
,26
2.50
,26
,26
,26
,50
.50
2.50
Column Temp.
35
35
23
35
35
35
35
35
23
35
35
35
35
35
23
True Cone, (yg/ml)
Column SO^" N03~
20
20
20
ho
ho
ho
ho
80
80
80
80
80
80
Nitrate
Interference
Old
New
New
Old
Old
Old
Old
New
New
Old
Old
New
New
New
New
20
20
20
ho
ho
ho
1*0
ho
ho
80
80
80
80
80
80
0.0
0.0
+5.7
+1.1
+3.6
+3.2
+2.
+0.
• 5
.7
+1.8
+3.2
+h.o
+3.0
+U.3
+1.7
+1.8
Retention Times (seconds):
Old column
New column
380
657
NO 3
220
478
At
160
179
-------
the old column the increase averaged 3.3 +_ .6% and for the new
column, 2.2 + 1.355. We conclude, therefore, that a small positive
• • *
bias in sulfate results is unavoidable using the ion chromatograph
with the eluent, flow rates and temperatures studied. These
findings provide at least partial explanation for the high results
noted in evaluating the ion chromatograph for sulfate determination.
IX. INTERMETHOD COMPARISON WITH ATMOSPHERIC SAMPLES
A. Introduction
Twenty-four hi-vol filter samples collected on Gelman EPA Grade
filters were selected for use in comparing analytical results among
the sulfate methods evaluated in the current study. These include
T>
Method 75, Colovos MTB, MRT-MTB, SulfaVer and the Dionex ion chroma-
tographic methods. In addition, the samples were analyzed by the
7 9
AIHL microchemical method with ion exchange pretreatment.
The samples analyzed were obtained from the California Air Resources
Board, They were selected from a set of 50, with five collected
at each of 10 sites throughout California. Samples were visually
graded into categories "light", "medium" and "heavy" loadings.
Where possible, samples from at least two of these loading categories
at each site were used for this study (Table 50). The samples in-
cluded an equal number collected within and outside of the South
Coast Air Basin.
One-half of each 8 x 10" filter was extracted by 30 minute ultrasonic
extraction with final volume 200 ml. The filtered, aqueous extract
- 12U -
-------
Table 50
Description of 2k Hour Hi-Vol Filter Samples for Intermethod Comparison8"
Number of Filters
Site Light Medium Heavy
^™^^*^aBt^B^^B~* ^^^^•^^••^MMHM *-*4II^MdMlblp-
Sacramento 11 i
Fresno 01 2
San Diego 021
San Francisco 030
Los Angeles 002
Long Beach 002
Ontario Oil
Pasadena 002
Santa Ana Oil
San Bernardino 002
a. All samples collected between 7/12/77 and 9/22/77 using Gelman EPA
Grade glass fiber filters.
- 125 -
-------
was analyzed successively by each method with three determinations
made on separate days.
B. Results
The results, expressed as yg/ml of aqueous extract, are given in
Table 51. The undiluted extracts covered the concentration range
from ca. 10 to 150 yg/ml. The values shown for Method 75, Dionex
TD
1C, MRI-MTB and SulfaVer methods were obtained without dilution
except for samples >_ 85 yg/ml which were diluted by a factor of 2
before analysis. Analyses by the Colovos MTB and AIHL microchemical
method employed samples diluted into the range 1-10 and 1-15 yg/ml,
respectively.
The results are compared as ratios, of means, relative to results by
Method 75, in Table 52. Average results agreed within 10$ for all
methods, with all methods showing somewhat higher values, compared
to Method 75 • The precision of the methods with atmospheric samples
is expressed by the median and range of the coefficients of variation.
R
All methods show median C.V. values < 6%. The SulfaVer method showed
both the highest ratio of mean and the poorest precision.
A more detailed comparison for the methods evaluated in this program
is given in Figure 31. The results are nearly identical to those
by comparing ratios of means since intercept values are small. All
methods show slightly higher results compared to Method 75, throughout
the concentration range. Except at the lowest concentrations there is
little scatter in the results.
- 126 -
-------
Table 51
Results of Intermethod Comparison with Atmospheric Samples (yg/ml)
Sample
_JD
2B
7D
1C
IE
ItC
U
2A
ItF
IB
10D
2D
3D
3A
9F
7C
8C
3C
6G
10Aa
' 5Ba
6Ba
9Ea
5Aa
8Ea
Method 75
11.5 ± 0.3
13.5 ± 1.1
13.7 + 0.3
16.6 ± 1.0
17.5 ± 1.2
20.6 ± 0.3
21.3 ± 1.3
22.2 ± 0.6
23.2 ± 0.6
28.8 ± 0.8
32.2 ± 0.9
35.8 ± 0.6
38.5 ± 0.8
39.2 + 0.3
51. U ± 0.6
53.3 ± 0.3
5U.6 ± 0.8
67.8 ± 2.2
85.8 ± 0.9
92. U +_ 2.5
102.8 ±1.0
103-5 ± 1-5
107,9 i i.o
150.0 ± 2.U
SulfaVer
13.1 ± 0.5
lU.3 ± 1.3
13-5 ± 1.0
12.3 + 0.3
15.0 ± i.o
22.0 ± 2.0
2U.2 ± 1.3
23.1 ± 1.6
25.2 ± 1.9
29.8 ± 2.7
38.1 ± 1.6
39. U ± 0.9
Ul.6 ± 2.9
hk.2 + 0.9
60.3 + 3.1
61.5 + 2.2
59.1 4. 1.6
71.1 +_ 0.7
102. U +_ 3.6
97.^ +_ 5-1
111.8 + 7-3
110.7 ± 6.5
117.9 ± 6.2
163.0 +_ 2.6
MRI-MTB
11.7 ±0.5
12.5 ± 0.7
10.5 + 1.0
8.0 +_ 0.5
12.9 + 2.0
21.2 + O.U
23.9 ± U.7
23.0 + 0.1
27.0 +_ 1.6
28.7 ± 1.5
36. U +_ 0.1
37.6 +_ 0.5
Mt.8 +_ 0.8
U3.7 i 0.6
53.8 +_ i.U
57-6 + 0.6
60. U +_ 2.2
70.3 + l.l
89.7 ± 0.9
103.1 + 0.9
106.2 + 1.1
111.8 +_ l.O
113.8 + 2.8
153.0 +_ 2.9
Dionex 1C
1^.0 +_ 1.0
15-3 ± 0.8
lU.U +_ 1.0
9-5 ±1.3
15.3 ± 0.8
21.8 ± 1.5
2U.7 ± l.l
25.1 ± 1.3
25-3 ± 1.2
30.9 ± 0.2
36.2 ± 1.6
Uo.O ± 1.5
h3.2 ± 1.7
kl.3 ± I.U
5U.8 ± 2.1
58.7 ± 0.8
6l. U ± 2.U
71.9 ± 0.8
9U.2 ± 0.9
97. U ± l.l
107.8 ± i.U
113.1 ± 0.7
113.1 ± 1.8
16U.O ± 3.1
Colovos-
MTB
lU.9 ± 0.6
15.1 ± 0.8
lU.l ± 1.2
13.7 ± 1.3
15.1 ± o.u
20. U ± 2.0
23.2 ± 0.9
2U.U ± 0.1
2U.9 ± 0.2
29. U ± 0.7
31.8 ± 2.5
37-9 ± 0.6
39-9 ± U.9
U2.0 ± 1.6
5U.1 ± 2.1
55-9 ±1.6
57.0 ± 2.8
68.9 ± 3.1
86.6 ± 1.3
97.5 ± 3.8
105.9 ± i.o
10U.2 ± 3.2
109.1 ± U.2
151.1 ± 5-U
AIHL
Micro
13. U ± 2.7
15.0 ± 1.5
13.7 ± 1.5
10.6 ± 3.8
15. U ± 2.0
21.3 ± 2.U
2U.2 ± 2.5
2U.O ± 2.5
25.3 ± i.o
30.1 ± 1.1
36. U ± 0.8
U0.6 ± 0.1
U3.0 ± O.U
U5.0 ± 0.6
57.6 ± I.U
58.8 ± i.o
59.5 ± O.U
72.2 ± 1.6
92.7 ± 2.0
98.7 ± 0.5
109-7 ± 2.U
109.7 ±2.5
111.0 ± O.U
15U.U ± 1.5
_
a. Samples diluted by factor of two before analysis by Method 75, the SulfaVer ,
MRI-MTB and Dionex 1C methods.
- 127 -
-------
Table 52
Average Agreement and Precision of Methods with Atmospheric Samples
Method 75
SulfaVerR
Dionex 1C
MRI-MTB
Colovos-MTB
AIHL Micro
Ratio of
1.00
1.09 +
1.08 +
1.05 +.
1.03 +.
1.06 +
Means
.01
.01
.01
.01
.01
Median
C.V. (%}
2.2
5-3
3.9
1.9
3.9
2.3
Range
c.v. (%r
0.6 to 8.1
1.0 to 9.1
0.6 to 13.7
0.3 to 19.7
O.U to 12.3
0.3 to 35.8
a. Results expressed relative to those for AIHL Method 75- Errors are
calculated as the standard deviation of the ratio of two dependent
variables:
S.D. ( ) . ^var. ( ) and
b. From three determinations on each of 2k samples.
- 128 -
-------
16Or- SULFAVJEB = -O.57O+1.10 (TURBID.)
r = 0.998
Sy.x = 3.00
120
SULFAVER 80
(jig/ml)
40
160 r- MRI-MTB = -0.759+1.06 (TURBID.)
r = 0.997
Sy.x = 3.43
120
MRI-
MTB 80
Oig/ml)
40
8
160 r-
120
DIONEX
1C 80
40
40
DIONEX-IC
r
Sy.x
80
120
160
40
80
120
160
-0.022+1.08 (TURBIDJ
0.998
2.76
160
120
COLOVOS
MTB 80
(jug/ml)
40
I
I
r-COLOVOS MTB = 0.774+1.01 (TURBID,)
r = 0.999
Sy.x = 1.72
40 80 120 160 40 80 120
TURBIDIMETRIC, METHOD 75 tyig/ml) TURBIDIMETRIC, METHOD 75
Figure 31
SCATTER DIAGRAMS OF RESULTS WITH ATMOSPHERIC SAMPLE USING FIVE SULFATE METHODS
160
-------
References
1. B. R. Appel, E. L. Kothny, E. M. Hoffer and J. J. Wesolowski, Comparison
of Wet Chemical and Instrumental Methods for Measuring Airborne Sulfate,
Interim Report. EPA-600/2-76-059 (1976).
2. B. R. Appel, E. L. Kothny, E. M. Hoffer and J. J. Wesolowski, Comparison
of Wet Chemical and Instrumental Methods for Measuring Airborne Sulfate,
Final Report. EPA-600/7-77-128 (1977).
3. Selected Methods for the Measurement of Air Pollutants, Public Health
Service Publication No. 999-AP-ll (196U).
it. Technicon Industrial Method 226-72W.
5- E. M. Hoffer, E. L. Kothny and B. R. Appel, Simple Method for Microgram
Amounts of Sulfate in Atmospheric Particulates. Accepted for publication
in Atmospheric Environment, 1978.
6. E. M. Hoffer and E. L. Kothny, A Micromethod for Sulfate in Atmospheric
Particulate Matter, Air and Industrial Hygiene Laboratory Report No. 163,
California Department of Health, July 197^-
7. C. Bros set and M. Ferm, "An Improved Spectrophotometric Method for the
Determination of Low Sulfate Concentration in Aqueous Solutions", Swedish
Water and Air Pollution Research Laboratory, ^02, 2U Gothenburg, Sweden
(197*0.
8. Barium Chloranilate Method for Determination of Sulfates in the Atmosphere,
March 1976. Prepared for U.S. EPA Environmental Monitoring and Support
Laboratory, Research Triangle Park, KG.
9. Hach Chemical Company.
10. Tentative Method for the Determination of Sulfates in the Atmosphere
(Automated Technicon II Methylthymol Blue Procedure) Environmental Protection
Agency, Quality Assurance Branch, July 15, 1977.
11. G- Colovos, et al, Anal. Chem, hQ_ 1693 (1976).
12. H. Small,et al, Anal. Chem. Uj_ 1801 (1975).
13- R. T. Sheen, et al, Ind. Eng. Chem. (Anal. Ed.) J_ 262 (1935).
lit. Standard Methods for the Examination of Water and Waste Water, lUth Ed. (1975).
15. Brochure prepared by the Parr Co., Moline, 111. (Circa 1900), unpublished.
130
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APPENDIX A
AIHL Method
DETERMINATION OF SULFATE IN HIGH VOLUME PARTICULATE
SAMPLES: TURBIDIMETRIC BARIUM SULFATE METHOD*
Analyte; Sulfate Method No; 61
Application; Air Pollution Range; 2 to 40 yg sulfate/m3
Matrix: Air Lower Detection
Limit: 50 ug sulfate/20 ml
Procedure; Collection on filter by high- solution
volume sampler, extrac-
tion with water followed Precision: 5 to 11% coefficient
by turbidimetric analysis , of variation
Date First
Issued; December 1974
Dates Revised; April 1975, February 1976 and July 1976
1. Principle of the Method
1.1 Atmospheric suspended particulate matter is collected over a 24-hour
period on a 20 by 25-cm (8 by 10-inch) glass fiber filter by using a
high-volume sampler. This method can also be used for samples collec-
ted on cellulose filters.
1.2 A water extract of the filter sample is treated with barium chloride
to form a barium sulfate colloidal suspension. The turbidity of the
suspension is measured spectrophotometrically at 500 nm.
1.3 The water extract can also be used for analysis of other water soluble
species, e.g. N03~, Cl"~, Na+, NH4+.
*AIHL modification of Public Health Service Method (Ref. 1).
Underlined sentences are changed from the February 1976 revision of Method 6l.
Prepared by staff of the Air and Industrial Hygiene Laboratory, State Depart-
rcnt of Health, Berkeley, Californ^
- 131 -
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No. 61
2. Range and Lower Detection Limit
2.1 Aliquoting is adjusted so that samples containing 2 to 40 ug sulfate/ra?
(the expected range of atmospheric samples) can be measured.
2.2 The lower detectable concentration of the turbidimetric analytical
procedure is 50 yg of sulfate in 20 ml solution.
3. Interferences
3.1 Measurement is dependent upon the stability of the suspension of col-
loidal barium sulfate particles, size of particles, sulfate concentra-
tion, barium ion strength, pH and temperature. These parameters must
be closely controlled to avoid obtaining low and inconsistent results.
Addition of glycerol acts as a stabilizer for the colloid, while alco-
hol promotes precipitation by reducing the solubility of barium sulfate.
Use of solid crystals of BaCl2 eliminates the problem of barium ion
strength and solution aging. Sulfate concentration is maintained
within the limits of the method, and pH is controlled by addition of
dilute HC1. Variations in temperature between 20 to 30°C do not appear
to have a significant effect. Vigorous shaking of the solution during
the addition of barium chloride promotes the formation of finer par-
ticles that stay in suspension longer.
3.2 Sulfur-containing anions are generally strong positive interferents
probably due to air oxidation to sulfate. Colloidal clay interferes
strongly but in a direction apparently dependent on the sulfate/inter-
ferent ratio. Table 1 summarizes results of a recent AIHL study (ref. 2).
3.3 Glass fiber filters are not sulfate free. The amount of sulfate depends
on the manufacturer's filter types and lots. For example, the MSA Type 1106 BH
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No. 61
3. (cont)
filters have been found to contain up to 4 mg sulfate per 20 by 25-cm
sheet. This sulfate can be removed by water wash prior to sampling if
desired. When this is not practical, as is the case for many monitoring
purposes, determine the background sulfate concentration (section 7.3.6)
for every lot and type of sampling filter used and correct the results
accordingly.
3.4 Frequently the aqueous extract containing the sulfate shows background
coloration and/or turbidity which may interfere with the analysis.
These interferences are accounted for by measuring the absorbance (A^)
of the filtrate and glycerol-alcohol-acid mixture before the addition
of the barium chloride. This value is subtracted from the absorbance
(As) °f "t^6 sample after the addition of barium chloride.
4. Precision and Accuracy
4.1 The precision of the method was established at AIHL by three determina-
tions on each of the extracts from 12 high-volume atmospheric samples
(ref. 2). Extracts were diluted into the optimal concentration range
of the method. Under carefully controlled conditions, a coefficient
of variation of 5% was found. This compares to the value 5% given in
ASTM method D516 (ref. 3) and to the value 11% reported in the Public
Health Service method (ref. l).
U.2 The extraction efficiency of the analytical method was recently evalu-
ated at AIHL utilizing exhaustive extraction of ten 2U_-hour samples
collected in Southern California. The mean recovery was 96.! + 1.2$.
- 133 -
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No. 61
4. (cont)
Also MSA 1106 BH and Staplex TFA 810 filters were spiked with known
amounts of sulfate salts and recoveries close to 100% were established,
5. Equipment
5.1 High-volume sampler. A motor blower filtration system with a sampling
head which can accomodate a 20 by 25-cm glass fiber filter and capable
of sampling at an initial flow rate of about 1.7 nrVmin (60 ft-Vmin).
5.2 Filters. Use 20 by 25-cm (8 by 10-inch) glass fiber filters of low
sulfate content.
5.3 Refluxing Apparatus. Use 125 ml flask with ground glass joint, a
reflux condenser and a hot plate.
5.4 Filtering Funnel and Whatman No. 42 filter paper.
5.5 Cuvettes. Matched 20 mm or 1 inch cuvettes.
5.6 Pipettes. Use 20, 5 ml and other sizes as required.
5.7 Spectrophotometer. Capable of measuring at 500 nm with a bandpass of 16 nm
or less.
5.8 Filtrate Receivers. 100 ml glass-stoppered graduated cylinders.
6. Reagents
All reagents should be made from ACS analytical-grade chemicals.
6.1 Hydrochloric acid (10 N) . Add carefully 80 ml of concentrated hydro-
chloric acid to 20 ml of distilled water in 100 ml glass stoppered
graduate cylinder and dilute to mark with water.
6.2 Glycerol - alcohol - acid solution. Mix 20 ml of glycerol with 40 ml
of reagent grade 95% ethyl alcohol and 15 ml of 10 N HCl.
Caution: Do not use denatured alcohol.
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No. 61
6. (cont)
6.3 Barium chloride. BaCl2 • 2 H20 Crystals, 20-30 mesh. J. T. Baker
Cat. No. 0974 or equivalent.
6*4 Standard sulfate solution (100 ug sulfate/ml). Dry anhydrous sodium
sulfate at 105°C for 4 hours and cool in a desiccator. Dissolve
0.148 g of the dried anhydrous sodium sulfate in distilled water and
dilute to 1 liter. This solution contains 100 pg sulfate per ml.
7. Procedure
7.1 Sampling. Using the high-volume sampler, collect the particulate matter
from approximately 2,000 m3 of air. Twenty-four hours is the usual
sampling period. Note and record the airflow rates at the start and
end of the sampling period.
7.2 Sample Preparation - The sample filter should be delivered to the
laboratory unfolded in a glassine envelope. An aliquot of the
filter is taken for analysis. (Appendix 1 discusses sectioning
the filter for various analyses). One-fourth of the filter
{Quadrant A as shown in Appendix 1) is cut into about 5-cm lengths
for ease in handling and placed into the 125 ml boiling flask con-
taining 50 ml of distilled water. Hie sample is refluxed for 60
minutes. The hot solution is filtered through a Whatman No. 1*2
filter paper which has been previously rinsed free of sulfate with
at least 50 ml of boiling distilled water. The filtrate is collected
in a 100 ml glass-stoppered graduated cylinder. Both the boiling flask and
- 135 -
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No. 61
7. (cont)
sample filter are rinsed 3 times with about 10 ml each of boiling
distilled water. After cooling, the final filtrate volume is brought
up to 100 ml with distilled water.
7.3 Analytical Procedure
7.3.1 Pipette an aliquot of the filtrate, normally 20 ml, containing
50 to 1000 yg sulfate into a clean dry 25 ml glass stoppered
graduate cylinder. When a smaller aliquot is used, dilute to
20 ml with distilled water. Add 5 ml of the glycerol-alcohol-
acid solution and mix.
7.3.2 Pour a portion of the solution in a dry cuvette. Determine
the absorbance at 500 nm against distilled water and record as
A!.
7.3.3 Pour the sample solution in the sample cuvette back in the
cylinder. Add approximately 0.25 g of barium chloride crystals,
stopper the flask and shake it vigorously for 45 seconds to
dissolve the crystals.
7.3.4 Let the sample stand for exactly 40 minutes at room temperature
(20° to 30°C). Then gently mix the suspension by inverting the
graduated cylinder once and measure the absorbance (A2> of the
solution against distilled water as above. When large number
of samples are to be analyzed, add the BaCl2 crystals at timed
intervals (e.g. 1 min) with similar intervals between spectro-
photometer readings.
7.3.5 Analyze a standard sulfate solution as a control with each batch
'-.136 -
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No. 61
7. (cont)
of samples to detect gross variations in the analysis. Devia-
tions up to 5% from the standard curve are acceptable.
7.3.6 A correction for the background concentration of sulfate in the
filters must be made for each new lot of filters. This value
(B) must be the average of at least 5 determinations using 5
filters from each lot of 100 filters using the entire analytical
procedure (sections 7.2 and 7.3) and must be subtracted as
filter blank (section 9.2).
8. Standards and Calibration
8.1 Prepare standard from the 100 yg sulfate/ml standard solution
by pipetting respectively 0, 0.5, 1.0, 2.0, 3.0, 4.0, 6.0, 8.0, and
10.0 ml into 25 ml glass stoppered graduated cylinders. Bring the
volumes to 20 ml with distilled water. Analyze the standard solutions
as in section 7.3, but the determination of AI is unnecessary since
negligible values are always obtained.
8.2 Plot the absorbance readings (A2) on the vertical axis versus the corres-
ponding yg of sulfate on the horizontal axis using a rectilinear graph
paper.
8.3 The relation between absorbance and amount of sulfate should be linear
between 300 and 1000 yg. The slope of the curve in this range is cal-
culated by least squares and used in determining the amount of sulfate
in each sample. Below 300 yg, the relationship is non-linear and the
sulfate concentration must be determined graphically.
- 137 -
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9. Cc-icula tier.::
9.1 Air volu.T.0 calculation
a. For 3?jrplcc collected at altitudes less than 3000 feet a cove mean
sea level, uce the cnli'L-rated air flew rate, which is approximately
equsl to the flow rate under standard conditions of 760 Torr and
25°C.
b. For sar.ples collected at altitudes of 2000 feet or greater, cali-
brate the hirh-volune sc-npler using the A?3 procedure (U) vhich
corrects the flow rate to standard sea level conditions.
c. Using the flow rate determined in (a) or (b) above, calculate the
air volune from the sanplinr tine and the averare of the airflow
rates at the start and end of the sanplir.; period.
y - £^_Q2 x t
2
Where: Qx = airflow rate at start of sampling period (n3/2iin)
cubic feet per narrate x O.C2S32 = n3/rdr.
Qs = airflow rate at end of sanpling period (si2/2iin)
cubic feet per minute :<0.02832 = m3/nin
t = sampling period (ain)
V = sample volune in cubic meters (n3) at standard
conditions
9.2 Subtract Ai free. Ao and, calc^olatin? from the calibration ciarve
obtained in section 8, deternir.e the equivalent ^g of sulfate (C|
in the aliquot. Calculate the concentration of sulfate in the 20 by
25 cm filter sanple in Mg/E3 as follows:
- 138 -
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No. 61
9. (cent)
yg sulfate/m* = (Fl * F2 x C) - B
Where: Fi » total ml of filtrate _
ml of filtrate taken for analysis
sample area of filter sample
sample area of filter quadrant analyzed
C - yg sulfate in aliquot of sample taken
B - yg sulfate/20 x 25-cm filter blank
V » air sample volume in m^( determined
as in T 9.1.)
10. References
1. Public Health Service Publication No. 999-AP-ll, Selected Methods for
the Measurement of Air Pollutants; "Determination of Sulfate in Atmos-
pheric Suspended Particulates: Turbidimetric Barium Sulfate Method",
pp 1-1, U. S. Dept. of Health, Education & Welfare, PHS, Div. of Air
Pollution, Robert A. Taft Sanitary Engineering Center, Cincinnati,
Ohio 45226, May 1965.
2. Final Report, EPA Contract No. EPA 68-02-1660, "Comparison of Wet
Chemical and Instrumental Methods for Measuring Airborne Sulfate",
B.R. Appel, E.L. Kothny, E.M. Hoffer and J.J. Wesolowski, February 1976.
3. ASTM Method D5 16-68 (Method B) , "Standard Methods of Test for Sulfate
Ion in Water and Waste Water"; 1975 Book of ASTM Standards; Part 31;
Water, ASTM; Philadelphia, PA.
4- Standard Procedure for the Calibration of Hi-Vol Samplers and Plotting of
Flow Calibration Curves Corrected for Altitude, California Air Resources
Board, Sept. 1975, Sacramento, California.
- 139 -
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Appendix 1
Cutting of Glass-Fiber High-Volume Filters
1- Remove the glass-fiber filter from the shipping envelope.
2. Using a clean cutting tool, preferably stainless steel, cut the filter in
half. Then cut one half into two equal Quadrants as shown in Figure 1.
cut
B
t
!0 c
I
20 cm
25 cm
Figure 1
3. Use quadrant "A" for the determination of sulfate (AIHL Method 6l ) and
nitrate (AIHL tfethod 66).
k. Use quadrant "B" for the determination of lead (AIHL 1-fethod 5^).
5- Use half "c" for the determination of benzene-soluble organics (AIHL
Method 67).
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Table 1
The Effect of Potential Interferents in the BaCl2 Turbidimetric Method3
Interferent
Sulfide
Sulfite
persulfate
thiosulfate
bicarbonate
phosphate
silicate
calcium
lead
colloidal clay
p-benzoquinone (a yellow
chromophore used to simu-
late a yellow extract)
Sulfate/Interferent Ratio
2:1 (w/w)
0.66:1 (w/w)
•f
0
0
0
•H-
0
0
0
0
0
a. + indicates > 10% increase in sulfate
44- indicates > 25% increase in sulfate
« indicates > 25% decrease in sulfate
0 indicates < 10% change in sulfate
b. . sulfate concentration 20 pg/ml
Source: Ref. 2
- lUl -
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METHOD 61. TURBIDIMETRIC SULFATE - ADDENDUM
1. Limit of Detection
The method specifies that the lower detection limit is 50 tig per aliquot.
This corresponds to a net absorbance of 0.03, i.e., A2 - AJ.. Since A^
may be as large as 0.07, the chemist and section leader should carefully
examine any AS value smaller than 0.10 absorbance units, with the thought
that the net absorbance may be less than the limit of detection. In any
case, all A2 - Aj values of 0.03 units or less should be considered as
being less than 50 yg sulfate.
2. Range of the Method
The range of the method is given as 2 to kO jug/m3, equivalent to 200 to
UOOO^g per aliquot. Actually, the curve is linear between 300 and'1500
Mg sulfate, corresponding to absorbances from 0.10 to 0.90. (Note that
the standards described in Method 6l do not covor this range. It should
be modified to include 1200 and 1UOO ug standards.) The optimum reading,
from an instrumental standpoint, is 0.^0 absorbance units. The following
protocol should be adopted:
a. Aliquots shall be adjusted to an A2 value of Q.kO. Samples giving A2
values less than 0.10 or greater than 0.90 must be rerun, using an
appropriate aliquot size.
b. Standards greater than 1500 wg shall not be run, since they adversely
affect the linear regression line.
c. Chemists shall not record, as a reportable result, A2 - Aj. values > 0.90
nor < 0.10, unless in the latter case, a 20 ml aliquot was used.
- 1U2 -
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3« Analytical Procedure
There should be no deviation from the written procedure. If circumstances
should require the section leader to temporarily modify the procedure, he
should instruct the chemist to flag these results and should, by memo, ex-
plain the circumstances to his group leader, the QA chairman and the data
handling section.
This memo should be attached to, and become a part of, the chemist's and
section leader's copy of Method 6l.
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APPENDIX B
AIHL Method
DETERMINATION OF SULFATE IN HIGH VOLUME PABTICULATE
SAMPLES: SIMPLIFIED AND IMPROVED TURBIDIMETRIC
BARIUM SULFATE METHOD*
Analyte: Sulfate Method Ho: 75
Application: Air Pollution Working Range; 1^0 to lUOO yg
sulfate/20 ml
Matrix: Air
Detection Limit; 50 yg sulfate/20 ml
Procedure: Collection on filter by solution
high-volume sampler,
extraction with water Precision; <_ 6% coefficient of
followed by turbidi- variation in working
metric analysis range
Date First Accuracy: Within k%, on average,
Issued: September 1978 using EPA Audit Strips
1. Principle of the Method
1.1 Atmospheric suspended particulate matter is collected over a 2^-hour
period on a 20 by 25-cm (8 by 10-inch) filter by using a high-volume
sampler.
1.2 A water extract of the filter sample is treated with barium chloride
to form a barium sulfate colloidal suspension. The turbidity of the
suspension is measured spectrophotometrically at 500 nm.
1.3 Results are dependent upon the stability of the suspension of colloidal
barium sulfate, particle size, barium chloride crystal and aggregate
size, pH and temperature. Glycerol acts as a stabilizer for the colloid
while alcohol promotes precipitation by reducing the solubility of
barium sulfate.
l.U Barium sulfate formation and turbidity measurement are done in test
tubes, thereby eliminating all sample transfers.
*The procedure was developed by E. M. Hoffer and is a revised version of
AIHL Method 6l. Evaluation of the procedure is given in Reference 1.
Prepared by staff of the Air and Industrial Hygiene Laboratory, State Department
of Health Services, Berkeley, California.
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2. Range and Detection Limit
2.1 The detection limit concentration of this turbidimetric analytical
procedure is 50 yg of sulfate in 20 ml solution. The working range
is from 1^0 to lUOO yg sulfate/20 ml solution.
3. Interferences
3.1 Variations in temperature "between 20 to 30°C do not appear to have
a significant effect.
3.2 Sample coloration and/or turbidity may interfere with the analysis.
These interferences are minimized by measuring the absorbafcce (AI)
of the filtrate plus glycerol-alcohol-acid mixture before the addition
of the barium chloride. This value is subtracted from the absorbance
(A2) of the sample after the addition of barium chloride. In spite
of this correction, interference may persist. Colloidal clay, used
to simulate the source of turbidity in some samples, is a strong
negative interferent. Yellow, water-soluble organics, isolated from
atmospheric particulate matter, show a small negative interference
at low sulfate concentration (Table 1).
3.3 Sulfur-containing anions are generally strong positive interferents
o
probably due to air oxidation to sulfate .
3.U Glass fiber filters contribute to observed sulfate both from a "blank"
2
value and by artifact sulfate formation . Artifact
sulfate can be minimized by employing pH neutral filters (e.g. quartz
fiber). With all filter types, the background or blank sulfate
concentration should be measured (Section 8.3.3) for every lot and
type of sampling filter used and the results corrected.
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1*. Precision and Accuracy
U.I The precision of the method was established "by three determinations
on each of the extracts from 2k high-Trolume atmospheric samples
ranging in concentration from 2hO to 1500 ug sulfate per 20 ml
solution. The median coefficient of variation was 2.2% (range 0.6
to 8.1$). This compares to the value 5% given in ASTM method D5l6
and to the value 11$ reported in the Public Health Service method.
k.2 Accuracy was established by analyzing EPA audit strips (i.e. filter
strips loaded with known quantities of sulfate). For solutions in
the range 300 to 1700 ug/20 ml, the ratio of observed to theoretical
concentration ranged from 1.00 to 1.05 with mean value l.OU.
5. Working Range
5.1 Working range is defined as the sulfate concentration range providing
approximately constant coefficient of variation and "relative accuracy".
The latter indicates the accuracy of the method relative to the value
obtained in the optimal concentration range of the method. This is
determined using a pooled, concentrated atmospheric sample extract,
diluted to varying degrees.
5.2 This procedure yielded a relative accuracy within J% in the con-
centration range ikO to 1^00 ug sulfate/20 ml solution with a
C.V. of <_ 6%.
6. Equipment
6.1 High-volume sampler. A motor blower-filtration system with a sampling
head which can accomodate a 20 by 25-cm filter and capable of sampling
at an initial flow rate of about 1.7 m3/min (60 ft3/min).
6.2 Filters. 20 by 25-cm (8 by 10-inch) filters.
6.3 Ultra Sonic bath. For example, Bransonic Model 32.
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6.U Fine glass frit, 30 ml capacity
6.5 Fisher filtrator
6-6 25 x 150 mm Teflon-lined screw capped test tubes. The tubes must be
unscratched. Add a fiduciary mark to permit reproducible positioning
in the spectrophotometer. Test tubes are further pre-selected as
follows: a) fill all test tubes with distilled water, b) using a
single beam spectrophotometer, select any tube for an initial
reference and determine the tube with highest % T, c) label this
tube and use as blank for all sample determinations, and d) match
all other test tubes with the blank within 2%.
6.1 Pipettes. 20, 5 ml and other sizes as required.
6.8 Spectrophotometer. Capable of measuring at 500 nm with a bandpass
of 20 nm or less, using 1 inch cells.
6.9 Filtrate receivers. 60 or 100 ml plastic bottles with tightly
fitting caps.
Reagents
Make all reagents from ACS analytical-grade chemicals.
7.1 Hydrochloric acid (10 N). Add carefully 80 ml of concentrated
hydrochloric acid to 20 ml of distilled water in 100 ml glass
stoppered graduate cylinder and dilute to mark with water.
7.2 Glycerol-alcohol-acid solution. Mix 20 ml of glycerol with kO ml
of reagent grade 95$ ethyl alcohol and 15 ml of 10 N HC1. This
solution is stable for up to 6 months. Caution; Do not use
denatured alcohol.
7.3 Barium chloride. BaCl2-2H20, 20-30 mesh if available. Reference 1
details an evaluation of barium chloride mesh and crystal size, both
of which influence the calibration curve. In general, use of BaCl2-2H20
not graded for turbidimetric analysis yields a calibration curve with
reduced slope and increased scatter.
-------
T.k Standard sulfate solution (100 pg sulfate/ml). Dry anhydrous sodiuti
sulfate at 105°C for U hours and cool in a desiccator. Dissolve
0.1^8 g of the dried sodium sulfate in distilled water and dilute
to 1 liter. This solution contains 100 yg sulfate per ml.
8. Procedure
8.1 Sampling. Using the high-volume sampler, collect the particulate
matter from approximately 2,000 m^ of air. Twenty-four hours is
the usual sampling period. Note and record the airflow rates at
the start and end of the sampling period.
8.2 Sample Preparation. The sample filter should be delivered to the
laboratory unfolded in a glassine envelope. Take an aliquot of the
filter for analysis. (Appendix 1 discusses sectioning the filter
for various analyses). Cut one-fourth of the filter (Quadrant A
as shown in Appendix l) into about 5-cm lengths for ease in handling.
Place it in a 50 ml glass stoppered Erlenmeyer flask containing 50 ml
of distilled water and then in an ultrasonic bath for 30 minutes.
A batch of 18 samples may conveniently be handled at once. Filter
the solution through a clean, fine porosity fritted glass filter
(30 ml volume) into a 60 ml polyethylene bottle using a Fisher
filtrator. After discarding filter pulp, carefully wash the frit
free of sulfate with distilled water and suction it dry. Washings
are not added to the extract.
8.3 Analytical Procedure
8.3.1 Pipet aliquots of the filtrates, normally 20 ml, into a
series of clean and dry screw capped test tubes. When a
smaller aliquot is used, dilute to 20 ml with distilled
water. Add 5 ml of the glycerol-alcohol-acid solution and
mix slowly, inverting a batch of samples 6 times, taking
- 1U8 -
-------
about 2 seconds to invert, and waiting about 10 seconds
before re-inverting. Wait 10 minutes to permit escape of
bubbles.
8.3.2 Determine the absorbance at 500 run against distilled water
and record as Aj.
8.3.3 Add one scoop (approx. 0.25 g) of barium chloride crystals
at one minute intervals to the batch of samples, following
each addition by mechanical shaking. After adding BaCl2 to
the first sample, cap tightly and shake for 60 seconds at
90 oscillations/minute on an Eberhard (or equivalent) shaker,
with the tube lying on the plane of oscillation. While
shaking the first sample, time the addition of the BaCl2 to
the second sample and, when shaking of the first is complete,
immediately shake the second. Continue in this way for all
samples.
8.3A Let the first sample stand at 20 to 30°C for exactly Uo minutes
from the time of the initial BaCl2 addition. Then, gently mix
the suspension by inverting the sample test tube once and
measure the absorbance (A2) of the solution against distilled
water as above. Read each successive sample at 60 second
intervals to give each sample ^0+^1 minutes standing time.
8.3.5 A correction for the background concentration of sulfate in the
filters must be made for each new lot of filters. This value
(B) must be the average of at least 5 determinations using 5
filters from each lot of 100 filters using the entire analytical
procedure (Sections 8.2 and 8.3) and must be subtracted as
filter blank (Section 10.2).
-------
9. Standards and Calibration
9.1 For each batch of samples, prepare calibrating solutions using the
100 yg sulfate/ml standard solution. Pipet 0, 1.0, 2.0, U.O, 6.0,
8.0, 10.0, 12.0 and lU ml into separate test tubes and bring the volumes
to 20 ml with distilled vater. Analyze the calibrating solutions as
in Section 8.3.
9.2 Plot the difference in absorbance readings (A2~Aj) on the vertical
axis versus the corresponding pg of sulfate on the horizontal axis
using a rectilinear graph paper.
The relation between absorbance and amount of sulfate should be
approximately linear between 300 and 1000 ug/20 ml. By restricting
samples to this range, linear regression can be employed.
For analyses in the range 1^0 to lUOO yg/20 ml, a third order
regression equation is used of the form y = a + bx + ex2 + dx3
where x = yg/20 ml sulfate and y = absorbance.
10. CalcillatiOns
10.1 Air Volume Calculation
a. For samples collected at altitudes less than 2000 feet above
mean sea level, use the calibrated air flow rate, which is
approximately equal to the flow rate under standard conditions
(760 Torr and 25°C).
b. For samples collected at altitudes of 2000 feet or greater,
calibrate the high-volume sampler using the ARB procedure
which corrects the flow rate to standard sea level conditions.
c. Using the flow rate determined in (a) or (b) above, calculate the
air volume from the sampling time and the average of the airflow
rates at the start and end of the sampling period.
- 150 -
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Where: QL = airflow rate at start of sampling period (m3/min)
cubic feet per minute x 0.02832 = m3/min
Q2 = airflow rate at end of sampling period (m3/min)
cubic feet per minute x 0.02832 = m3/min
t = sampling period (min)
V = sample volume in cubic meters (m3) at standard
conditions
10.2 Subtract AI from A2 and, calculating from the regression equation
obtained in Section 8, determine the equivalent yg of sulfate (c)
in the aliquot. Calculate the concentration of sulfate in the 20
by 25 cm filter sample, in yg/m3 as follows:
yg sulfate/m3 = (F* * *~2 x C) - B
„ „ total ml of filtrate
Where* r
ml of filtrate taken for analysis
_ total sample area of filter sample
2 sample area of filter quadrant analyzed
C = yg sulfate in aliquot of sample taken
B = yg sulfate/20 x 25-cm filter blank
V = air sample volume in m3 (determined as in Sec. 10.l)
- 151 -
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11. References
1. Final Report, EPA Grant No. 805-M7-1 "Improvement and Evaluation of
Methods for Sulfate Analysis", B. R. Appel, E. M. Hoffer, M. Haik,
W. Wehrmeister, E. L. Kothny and J. J. Wesolowski, 1978.
2. Final Report, EPA Contract No. EPA 68-02-1660, "Comparison of Wet
Chemical and Instrumental Methods for Measuring Airborne Sulfate",
B. R. Appel, E. L. Kothny, E. M. Hoffer and J. J. Wesolowski,
February 1976.
3. ASTM Method D516-68 (Method B), "Standard Methods of Test for Sulfate
Ion in Water and Waste Water", 1975 Book of ASTM Standards, Part 31,
Water, ASTM, Philadelphia, PA.
U. Public Health Service Publication No. 999-AP-ll, Selected Methods for
the Measurement of Air Pollutants; "Determination of Sulfate in
Atmospheric Suspended Particulates: Turbidimetric Barium Sulfate
Method", pp. 1-1, U.S. Dept. of Health, Education and Welfare, PHS,
Div. of Air Pollution, Robert A. Taft Sanitary Engineering Center,
Cincinnati, Ohio ^5226, May 1965.
5. Standard Procedure for the Calibration of Hi-Vol Samplers and
Plotting of Flow Calibration Curves Corrected for Altitude, California
Air Resources Board, September 1975, Sacramento, California.
- 152 -
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Appendix 1
Cutting of Glass-Fiber High-Volume Filters
1. Remove the filter from the shipping envelope.
2. Using a clean cutting tool, preferable stainless steel, cut the filter
in half. Then cut one half into two equal quadrants as shown in
Figure 1.
cut
\
1
T
20 cm
i
, 25 cm * I
Figure 1
3. Use quadrant "A" for the determination of sulfate.
- 153 -
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Table 1
Interference Effect vith, the AIHL Method 75 (yg/ml Observed Sulfate)
Sulfate Level
UE/ml
Inter ferent Level b
Inter ferent
Colloidal clay
Organica
bicarbonate (HC(>3~)
10
A
8.8
1.6
9.4
0.9
10.2
0.2
B C
5.2 1.6C
2.3
9.9 9.4
0.3 0.3
10.1 10.0
0.7 0.6
D
2.9d
1.0
8.3 •
0.3
10.4
0.3
35
A
35.3
0.5
35.4
1.9
37.0
0.3
B
33.2
0.3
35.8
0,5
36.1
0.2
C
31.2
0.2
35.2
0.7
36.5
0.5
D
30.0
0.6
35.2
o.u
36.0
0.6
60
A
58.3
0.9
60.0
0.7
60.0
0.3
B
56.2
1.2
60.5
0.5
59.5
0.9
C
53.0
0.7
59.0
1.1
60.2
0.8
D
50.7
0.7
59.1
2.U
60.0
0.6
a. Mean of three determinations, third order regression, vith +. 1 ° values shown below mean.
b. Interferent concentrations: »
B
Colloidal clay (vg/ml)
Organics (Abs/cm at UOO nm)
bicarbonate (yg/ml)
c. Single value. Two trials yielded negative results.
d. Mean of two results. One value yielded negative results.
10
0.0125
3.8
25
0.025
7.5
50
0.05
15
75
0.1
30
-------
APPENDIX C
PROTOCOL FOR THE RUGGEDNESS TEST FOR
DETERMINATION OF SULFATE BY THE TURBIDIMETRIC METHOD
Introduction
Ten factors were selected to evaluate as variables in conducting the
turbidimetric method. The factors and the levels of each variable to be
studied are shown in Table C-l. In all trials, standard quantities of
sulfate are to be added to the samples to permit analysis in the approximately
linear region of the working curve.
The ruggedness test is designed to determine the sensitivity of the method
to variation in each of the factors studied, following AIHL Method 6l.
Experimental Plan
The design is a balanced incomplete block as described by Plackett and
Burman, with 12 runs for the ruggedness test, and three replicates for each
run. Each run will have 10 factors and a dummy factor, and each factor may
be either of two levels. The scheme for all runs is shown in Table C-2
with the level of each factor designated by a "+" or "-" as previously
defined in Table C-l.
A standard calibration curve with six points ranging from 300 yg SOit/10 ml -
2000 yg SO^/10 ml, plus 10 ml of water for each point was included for each
run. Following the design in Tables 1 and 2, half of the runs were read
with a B&L 70 spectrophotometer and a 20 mm cell, and the other half, with
a B&L 20 and 25. U mm cell.
- 155 -
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Table C-l
FACTORS FOR EVALUATION IN RUGGEDNESS TEST
A = Level of SO^
B = Level of Addition of S0^=
C = Age of Reagent Mixture
D = Varying Strength of Reagent
Mixture
E = Time After Adding Reagent
Mixture Until Mixing
F = Mixing before Absorbance
Reading lc»d
G = Addition of BaCl2
H = Mode of Shaking, after
Addition of BaCl2
I = Timing before Second
Absorbance Reading8-
J = Speetrophotoiaeter, cell length
and mode of mixing^
K = Dummy
Low (-)
100 jjg/10 ml
300 yg/10 ml
Nev (0-1 mo. )
(U ml + 1 ml of
ethanol)
1 min.
Gentle Mixing6
High (+)
1000 yg/10 ml
600 yg/10 ml
Old (2 years)
5 ml
10 min.
Vigorously for
20 sec.
scoop (ca. 0.125 g) 1 scoop (ca. 0.25 g)
Gently for U5 sec.
(l shake/second)
20 min.
B & L 20, 25. U mm
separate cells
Vigorously for
U5 sec.
UO min.
B & L 70, 20 mm
graduated cylinder
a. Following BaCl2
b. Sample and reagents mixed either in separate cells used for turbidity readings
or in graduated cylinders with tranfers to a single 20 mm cell for reading
turbidity.
c. The absorbance due to initial turbidity of sample plus the glycerin-alcohol-
HC1 "mixed" reagent before addition of BaCl2.
d. After transfer of solution to cuvet, entrapped bubbles can cause appreciable
error in absorbance.
e. Slowly add glycerol-alcohol-acid solution minimizing air entrainment. Mix
solution by inverting graduated cylinder slowly (about 2 seconds to invert).
After 10 seconds, invert again. Repeat for total 6 inversions.
-156-
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Table C-2
5
6
7
8
9
10
11
12
DESIGN OF RUGGEDNESS TEST&
Rim/Factor ^5.£p_E_F_G_HI_JK
1 + + - + + + ___ + _
2 +- + + + ___ + _ +
3 _ + + + ___ + _ + +
a. Plus and minus indicate levels of variable as given in Table C-l.
- 157 -
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Data Evaluation
Since the runs involve the deliberate addition of sulfate in each case, the
result for a given run is considered to be:
Run Result = Sulfate (observed)/Sulfate (expected)
The effect of variation of a given factor (e.g. A) over the range corre-
sponding to the "+" and "-" levels is determined by subtracting the mean of
all runs with "-" values for A from the mean results of all runs with "+"
values for A:
Effect of A = Run (1,2,U,5,6,10) - Run (3,7,8 9,11,12)
6 6
For evaluation, the following steps will be used:
1. Rank the effects (highest first)
2. Sum the variance (i.e., square of the effect) and calculate
the % of the variance in the turbidimetric method due to each
factor.
Quality Assurance
The addition of standard amounts of sulfate to a sample, while permitting use
of the nearly linear portion of the working curve, introduces a potential
error because of imprecision and/or inaccuracy in pipetting the standard
addition. For example, a 1% error in pipetting 300 ug sulfate leads to an
error of about Q% for a sample initially containing kO yg sulfate. Accord-
ingly, careful calibration of the volumetric equipment is essential.
- 158 -
-------
The standard addition/10 ml and the addition of the 10 ml of water and the
*
mixed reagent are added by Repipet , while the level of sulfate of 100 yg/
10 ml and 1000 yg/10 ml are by conventional pipet. The various concentra-
tions of standard sulfate for the turbidimetric calibration curve are also
pipetted with a volumetric 10 ml pipet. The standard addition/10 ml was
calibrated by weighing the 10 ml that are expelled by the Repipet. The
Repipet was adjusted to dispense 300 or 600 yg 30^"/10 ml with an accuracy
of + 0.5$.
*A device which attaches to a reagent bottle permitting variable and repro-
ducible dispensing of calibrated volumes of reagent.
- 159 -
-------
Bibliography
1. Plackett and Burman, "The Design of Optimum Multifactorial Experiments",
Bionetrika 33., 305 (19^6).
2. "Efficient Screening of Variables", Stowe and Mayer, Ind & Eng Chem 58.:
No. 2, 36 (1966).
3. "Statistical Techniques for Collaborative Tests", published by A.O.A.C.
(1973).
U. "Measurement of Atmospheric Sulfates: Evaluation of the Methylthymol
Blue Method", EPA-600A-76-015, March 1976.
- 160 -
-------
GLOSSARY
observed sulfate sample in experimental run including the level of
sulfate from a standard or field sample plus the standard addition
for the run.
Sn 9 Sr, -3 = observed sulfate values for 3 replicates for Run n.
J-l • £- •$ II • J}
S = average sulfate values from 3 replicates for Run n.
A "= standard addition for run n calibrated by weighing solution at ambient
temperature.
A . A 0 A _ = standard addition for three trials for Run n.
n.l, n.2, n.3
A = average of standard additions for three trials for Run n.
Ks = calculated value for the level of sulfate and standard addition for
n
Run n (factors A plus B in Table 1).
R = result for Run n as obtained by subtracting calculated sulfate from
n
that observed:
R = S" - Ks
n n n
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APPENDIX D
Protocol for SulfaVer IV Procedure
1. Determine initial transmittance (Tj) of sample in a 2 cm cuvet at 500 nm
using a B and L TO Spectrophotometer.
2. Tap SulfaVer IV pillows to settle contents. Cut off tops and carefully
transfer contents simultaneously to a set of 12 samples and/or standards
contained in 25 x 150 mm Teflon-lined screw cap test tubes. Simultaneous
transfer can be facilitated by using a tray in which pillows are clipped
at intervals corresponding to the space between test tubes. Inverting
the tray thereby empties contents of each pillow into a row of test tubes.
A set of standards is run daily.
3. Tighten caps on each, mount horizontally on a mechanical shaker which
oscillates inahorizontal plane (e.g., as supplied by Eberbach Corp.,
Ann Arbor, Ml) and shake for one minute at 90 oscillations per minute.
U. Beturn samples to a rack in a vertical position and allow to stand
for 20 minutes.
5. Transfer to a 2 cm cuvet and read transmittance (T2). Reading a set
of 12 samples and/or standards requires 6 minutes or less.
6. To reduce analysis time a second set of 12 samples can be started
during the 20 minute reaction time.
- 162 -
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APPENDIX E
TENTATIVE METHOD FOR THE DETERMINATION OF SULFATES
IN THE ATMOSPHERE (AUTOMATED TECHNICON II
METHYLTHYMOL BLUE PROCEDURE)
A tentative method is one which has been carefully drafted from available
experimental information, reviewed editorially within the Quality Assurance
Branch, and has undergone extensive laboratory evaluation. The method is
still under investigation and therefore, is subject to revision.
ENVIRONMENTAL MONITORING AND SUPPORT LABORATORY
U.S. ENVIRONMENTAL PROTECTION AGENCY
RESEARCH TRIANGLE PARK, NORTH CAROLINA 27711
March 1978
- 163 -
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1. Principle and Applicability
1.1. Ambient sulfates are collected by drawing air through a glass
fiber filter with a high volume pump. The filters are extracted with water
sonically or by refluxing and the extract is treated with barium chloride
and methylthymol blue (MTB) at a pH of 2.8. After the barium sulfate pre-
cipitates, the pH is increased to 12.4 and the unreacted barium forms a
chelate with the MTB. The uncomplexed MTB remaining is then measured colori-
raetrically at 460 nmJL'
1.2. The method is applicable to the collection of 24-hr samples in
the field and subsequent analysis in the laboratory.
2. Ran&e and Sensitivity
2.1. The range of the analysis is 3 to 95 fig SC^/ml. With a 50-ml ex-
tract from one-twelfth of the high volume filter collected at a sampling
rate of 1.7 m-Vmin (60 cfm) for 24 hr, the range of the method is 0.74 to
23.3^tg/m . The lower range may be extended up to 12-fold by increasing
the portion of the filter extracted. The upper limit may be increased by
diluting the sample with distilled water.
2.2. Using the procedure outlined, a concentration of 3 pig SO^/ml
will produce a scale deflection of 3% of full scale (signal/noise ratio
of 2).
3. Interferences
3.1. Sulfides, sulfites, and phosphates produce a positive interference
which is dependent on the concentration of sulfate and the interfering ion.
3.2. The interferences from cations are eliminated by passing "the sample
through an ion-exchange column.
4. Precision and Accuracy
4.1. A single laboratory's relative standard deviation based on the
analyses of duplicate strips taken from several thousand filter samples
is + .
4.2. Adequate data for accuracy in the determination are not currently
available.
-------
5» Apparatus
5»1» .Sampling; Apparatus as specified in "Appendix B - Reference
Method for the Determination of Suspended Particulates in the Atmosphere
(High Volume Method),11 shall be used.1/
5.2. Analysis
5.2.1. Technicon II Analyzer; An automated analytical system
must be used for the determination of water soluble -.sulfate by this method.
Alkaline solutions of methylthymol blue decompose on exposure to air. The
method, therefore, cannot be adapted to a manual procedure. The Technicon
II Automated Analyzer System (manufactured by Technicon Instruments Corp.,
Tarrytown, New York 10591) consists of the following components:
5.2.1.1. Technicon Autoanalyzer Sampler IV
5.2.1.2. Proportioning Pump III; Either single speed or
two speed pump for rapid flushing.
5.2.1.3. Mixing Coils; One double 11-loop mixing coil 43 mm
(1.75 in.) long and 30 mm (1.25 in.) wide. One double 10-loop mixing coil
41 mm (1.63 in.) long and 30 mm (1.25 in.) wide. One 5-loop mixing coil
30 mm (1.25 in.) long and 30 mm (1.25 in.) wide.
5.2.1.4. Ion-Exchange Column; Interfering heavy metals
are removed by the use of an ion-exchange resin. Use Dowex 50W-X8, sodium
form, 300 to 850/im (20-50 mesh). The resin should be stirred into distilled
water and the fines discarded before they can settle. The resin should be
soaked before use, at least overnight, and may be stored under distilled
water until used. To pack a column, a small piece of glass wool is inserted
in one end of a piece of plastic tubing 10 cm (4 in.) long and 2.3 mm
(0.09 in.) I.D. A rubber pipette bulb is attached to the end of the tubing
containing the glass wool plug. The other end of the tubing is placed in
the soaked resin container and the rubber bulb operated until the tubing
is filled with resin. The column must be free of trapped air after filling
with resin. The resin column should be replaced after a full day's use.
5.2.1.5. Single Channel Colorimeter; A stable colorimeter
suitable for use at 460 nm with a band width of no greater than 18 nm at
half height.
5.2.1.6. Flow Cell; 15-mm path length flow cell.
5.2.1.7. Linearizer; The use of a linearizer is optional.
The sulfate response does not always conform to deer's Law. If the MTB solu-
tion (6.2.15.) is prepared with the optimum molarity and a barium chloride
- 165 -
-------
ratio a close approximation to Beer's Law is obtained, a linearizer is not
required. However, if a linearizer is available, it may be used.
5.2.1.8. Single Channel Recorder; Strip chart recorder
matched to the analyzer output.
5.2.1.9. Modular Digital Printer; Converts analog signal
from the recorder to digital printout. The use of the printer is convenient
but optional.
5.2.1.10. Pump Tubing; Flow rated tubing of the capacities
shown in Figure 1. Deviations from these flow rates are acceptable only
to the extent that a proper calibration curve and acceptable quality con-
trol checks are obtained. The use of silicone rubber tubing in place of the
standard pump tubing is highly recommended for the MTB and flow cell waste
lines. Pump tubing should be replaced every 21 days used.
5.2.2. Volumetric Flasks; 50, 100, 500, 1,000 ml capacity.
5*2.3. Pipettes; 2, 3, 4, 5, 6, 7, 8, 10, 15, 20, 25, 50 ml
volumetric; 10 ml graduated in 1/10 ml intervals.
5.2.4. Pyrex Glass Wool
5.2.5. Plastic Tubing; 10 cm (3.94 in.) and 2.3 mm (0.09 in.)
I.D.
5.2.6. Rubber Pipette Bulb
5.2.7. Buchner Funnels; Buchner style 150 ml capacity with fine-
pore fritted glass filter.
5.2.8. Vaccum Filtering Apparatus; Device which permits vacuum
filtering directly into the receiver. This consists of a bell jar with a
top opening, a side tabulation, and a bottom plate. The Buchner funnel pas-
ses through the top opening and is sealed to the bell jar with a stopper.
The bell jar should be tall enough to contain the polyethylene bottles used
for storing the samples. The vacuum connection is made using the side tubula-
tion. The filtering apparatus is shown in Figure 2.
5.2.9. Vacuum Pump; Any device which can maintain a vacuum of
at least 85 KPa (64 cm of Hg). Mechanical pumps or water aspirators may
be used.
5.2.10. Polyethylene Bont??s; Bottles with a capacity of 60 ml
(2 oz) fitted with polyseal caps.
- 166 -
-------
H
Connector
ir~!
n
22 Turn
•Mixing
Coil
1
f*~—
Debt
Ion Exchange
Column
jbbler
W
5 Turn
Mixing
Connector 1 1
B— 1
Coi
Wash
1
^ 1
\
20 Turn
• Mixing
SCoil
Waste
Waste
. cf
4
r
GRY GRY
BLK BLK
GRN GRN
BLK BLK
GRN GRN
BLK BLK
RED RED
ORN ORN
GRN GRN
Proportioning
Pump
1
(1.00)
« (°'32) S3
* (2-00) w,
* <°'32> 'a
« (°'32) Pec
(0.70)* Me
t
mple Air
jrer
mple
iter
agent Air
thy 1 thymol
Blue
(0.42) Sodium
""" Hydroxide
_ (2.00)*
fFlow Rates,
ml/min
*Silicone Pump Tube
Colorimeter
15 mm Tubular Flow Cell
460 nm
Figure 1. Autoanalyzer Flow Diagram for Sulfate Analysis.
-------
•Buchner Funnel with
Fine Pore Fritted Disc
To Vacuum Source
Polyethylene
Bottle
Bell Jar
Baseplate
Figure 2. Vacuum Filtering Apparatus,
- 168 -
-------
5.2.11. Glass Bottles (brown); 500-ral glass bottles with poly-
seal caps*
5.2.12. Graduated Cylinder: 10 and 100-ral capacities.
5.2.13. pH Meter; Capable of measuring pH to nearest 0.1 pH
unit over a range of 0 to 14.
5*3. Extraction; The samples may be extracted using either the reflux
or ultrasonic procedure.
5.3.1. Ultrasonic Extractions
5.3.1.1. Ultrasonic Gleaner; Of suitable size to process
the required number of samples and at least 7.6 cm (3 in.) deep.
5.3.1.2. Glass Bottles (clear); 60-ml (2-oz) glass bottles
with snap polyethylene covers.
5.3.2. Reflux Extraction
5.3.2.1. Erlenmeyer Flask; 125 ml with 24/40 £ joint.
5.3.2.2. Condenser; Water jacketed, 300 mm length with
24/40 S joints.
5.3.2.3. Hot Plate; Suitable for sample extraction (7.2.1.2. )<
5.3.2.4. Teflon® Sleeves; Sized to fit 524/40 joints.
6. Reagents
6.1. Sampling
6.1.1. Filter Media; Filter media as specified in "Appendix B -
Reference Method for the Determination of Suspended Particulates in the
Atmosphere (High Volume Method)/1 shall be used*!/ At least six randomly
selected filters from each lot should be analyzed for sulfate, and those
lots producing a blank value >1 /Ltg/ml should be rejected.
6.1.1.1. Determination of Filter pH; Cut a 58 cm2 (9 in.2)
section of glass fiber filter with a pizza cutter. Place the filter in a
125-ml Erlenmeyer flask. Add 15 ml of 0.05 M KCl (6.2.2.) and stopper the
flask. Stir with a magnetic stirrer for 10 min at 2=60 rpm. Determine the
pH of the extract.
- 169 -
-------
Obtain the pH for at least six randomly selected filters
of a given lot of filters and report the mean and standard deviations. The
pH value has an effect on accuracy of the collection procedures. Optimal
pH value of the filter extract is not presently known, but pH information
will be useful for historical purposes. Filters currently used in the National
Air Sampling Network (NASN) have a pH of 9.74 + 0.89.
6.1.1.2. Determination of Filter _SO&= Content; Measure the
sulfate content of at least six randomly selected filters from each lot
of filters. Cut a 7.6 x 20.3 cm (3/4 x 8 in.) strip from each filter using
a pizza cutter and a template. Follow the procedures for extraction and
analysis given in either sections 7.2.1.1. or 7.2.1.2. and 9.2.2. Calculate
the mean and standard deviations in p.g SOA=/in.2. The mean standard deviations
should not exceed 2.5 and 1.2 jug SO^/in.S respectively. The sulfate content
of filters in current use by NASN have mean and standard deviations of 2.1
and 1.1 pig S04~~ in.^, respectively.
6.2 Analysis
6.2.1. Sodium Hydroxide; ACS Reagent Grade.
6.2.2. Barium Chloride; ACS Reagent Grade.
6.2.3. Methylthvmol Blue (MTB); 3',3"-bis[S, N-Ms(carboxymethyl)
aminoj methyl thymolsulfone-phthalein pentasodium saltj 96% minimum by spectro
analysis; Eastman No. 8068 or equivalent. The purity of commercial MTB may
vary considerably. Each lot of MTB must therefore be analyzed following
the procedure described in 8.1.8.
6.2.4. Ethanol; 957, U.S.P.
6.2.5. Ammonium Chloride; ACS Reagent Grade.
6.2.6. Concentrated Ammonium Hydroxide; ACS Reagent Grade, 28
to 307. as NH3.
6.2.7. EDTA Tetra Sodium Salt; Tetra sodium ethylenediamine
tetraacetate, Technical Grade.
6.2.8. Sodium Sulfate; ACS Reagent Grade, anhydrous.
6.2.9. Concentrated Hydrochloric Acid; ACS Reagent Grade, 36.5
to 38.07. HCl.
6.2.10. Distilled Water; ACS Reagent Grade, having a specific
conductance of 2/u£2~l cm"1- or less..!/
- 170 -
-------
6.2.11. Potassium Chloride; ACS Reagent Grade.
6.2.12. Sodiun Hydroxide Solution (0.1 N); Dissolve 2.0 g of
sodium hydroxide in distilled water and make to 500 ml in a volumetric flask.
6.2.13. Hydrochloric Acid Solution (1.0 N); Add 8.3 ml of concen-
trated hydrochloric acid to water in a volumetric flask and make to 100 ml.
6.2.14. Barium Chloride Solution (0.0086 H): Dissolve 2.090 g
of barium chloride dihydrate (BaCl2 • 2H20) in' distilled water and make
to 1,000 ml in a volumetric flask.
6.2.15. Methylthymol Blue Solution (0.00038 M); To an amount
equal to 0.164 g of 1007. pure MTB (see section 8.2.8.) in a 500-ml volumetric
flask add successively 25 ml of barium chloride solution, 4 ml of 1.0 N
hydrochloric acid, and make to 500 ml with 95% ethanol. Store in a brown
glass bottle. Reagent prepared one day may be used on the following day
if stoppered and stored in the dark.
6.2.16. Buffer oH 10.1; Dissolve 6.75 g of ammonium chloride
(NH4C1) in 500 ml of distilled water. Add 57 ml of concentrated ammonium
hydroxide (Nt^OH) and dilute to 1,000 ml with distilled water. Adjust the
pH to 10.1 with additional NH^OH.
6.2.17. Buffered EDTA (wash solution)i Dissolve 40 g of tetrasodium
EDTA in the pH 10.1 buffer solution.
6.2.18. Stock Sulfate Solution (1,000 qg SO/rVml); Dissolve
1.4787 g of sodium sulfate (^2804), which has been heated at 105°C
for 4 hr and cooled in a dessicator over anhydrous magnesium perchlorate,
and dilute to 1,000 ml with distilled water. Store under refrigeration.
6.2.19. Blank Reagent Color Solution; To a. 500-ml volumetric
flask add 4 ml of 1.0 N hydrochloric acid and make to 500 ml with 95% ethanol.
6.2.20. Potassium Chloride Solution (0.05 M); Dissolve 3.7 g
of KCl in 1,000 ml of C02 free distilled water. The pH of this solution
should be 7.0+0.3.
6.2.21. Wettine Agent; A 30% solution of polyoxyethylene ether
of lauryl alcohol (BRIJ-35) or other suitable non-ionic wetting agent should
be added at the rate of 0.5 ml/liter to the wash and sample dilution water
supply.
- 171 -
-------
7. Procedure ,
7.1 Sampling: Sampling procedures as specified in "Appendix B - Reference
Method for the Determination of Suspended Particulate in the Atmosphere
(High Volume Method)" shall be used.1/
7.2 Analysis
7.2.1. Sample Extraction; The filters are removed from the fol-
der, opened flat, and cut into 1.9 cm x 20.3 cm (3/4 in. x 8 in.) strips
using a pizza cutter. The filter should be cut with the particulates face
up.
7.2.1.1. Ultrasonic Extraction; One or more filter strips
are placed in a 60-ml (2-oz) glass bottle. A random 5 to 10% of the filters
should be extracted in duplicate for use as quality control samples.^' Fifty
milliliters of distilled water is pipetted into each bottle. The bottles are
then closed with snap polyethylene caps. The samples are placed in the ultra-
sonic bath, which should be refilled before each set of extractions with
fresh cold tap water to the level of the liquid in the bottles. The ultra-
sonic bath is operated for 30 min. The extracts are immediately vacuum filtered
using the Buchner funnels and the vacuum filtering apparatus. The samples
are filtered directly into polyethylene bottles. The filters should not be
washed or squeezed, and the filtrates are not diluted. After filtering is
complete, the polyethylene bottles are capped with polyseal caps and stored
upright until analyzed. The samples are stable at room temperature for at
least 2 weeks.
7.2.1.2. Reflux Extraction; One or more filter strips are
folded and placed in a 125-ml Eerlenmeyer flask. Add 35 ml of distilled
water to the flask and connect to a 300-mm water jacketed condenser. Place
the flask condenser assembly on a hot plate and boil gently for 30 min.
Maintain cold water circulation through the condenser while the sample cools
to room temperature. Rinse the walls of the condenser with 5 ml of distilled
water and disconnect the flask. Decant the liquid in the flask directly
into the Buchner funnel of the filtering apparatus and filter into a glass
graduated tube with a 50 ml graduation mark. Rinse the filter in the flask
with a 5-ml portion of distilled water and add the rinse to the funnel.
Squeeze the filter with a glass rod to remove the remaining extract and
collect the filtrate. Repeat the rinse with a second 5-ml portion of distilled
water. Collect the filtrate and dilute to a volume of 50 ml with distilled
water. Transfer the sample to a 60-ml (2-oz) polyethylene bottle and cap
with a polyseal cap. Mix thoroughly. These samples are stable at room tempera-
ture for at least 2 weeks.
- 172 -
-------
7*2.2. Sample Analysis; A Technicon II Analyzer is employed
for analysis. A flow diagram and reagent flow rates are shown in Figure 1,
page 5. The absorbance is measured at 460 nm, and a flow cell with a path
length of 15 mm is employed. The sample turntable rate is 40 samples/hr
with a 12-sec wash time. The elapsed time between sample pickup and the
corresponding peak is approximatley 6 min. The instrument should be zeroed
and spanned following the manufacturer's directions.
The automatic analyzer is operated at the beginning of each day,
after a fresh ion-exchange column is installed, and prior to the first sample
analysis until a drift-free baseline is obtained. Analysis should be con-
ducted in a laboratory with reasonable temperature control since the method
is moderately affected by temperature.
7.2.2.1. Sample and Quality Control Standard Loading: Fill
the test cups with Camples and place on the turntable. One quality control
sample, a 50 ^g S04~/ral calibration standard (8.2.3.), and one or two water
blanks are included after every 10 samples. Establish a historical data
base and construct a quality control chart indicating 3(7 lower and upper
control limits for the 50 /ig S04=/ml standard*^/ The distilled water is
included after each 10th sample cup to correct for baseline drift. If the
sample extracts are highly colored or contain suspended particulate, a blank
must be run of the samples. This may be accomplished by replacing the MTB
solution (6.2.15.) with ethyl alcohol plus acid solution (6.2.19.) and per-
forming the analysis a second time. The sulfate values from the sample
blanks should then be used in calculating the final sulfate concentration.
If a linearizer is used (5.2.1.7.), the various standards
used for calibration (8.2.3.) are programmed through the linearizer so that
sulfate concentrations are printed directly in micrograms per milliliter
by the digital printer.
7.2.3. System Maintenance; After completing the final analysis,
the system should be cleaned with the EDTA solution. With the analyzer operat-
ing, place the MTB line and NaOH line in distilled water for 2 to 3 min.
Remove the ion exchange column and replace it with transmission tubing.
Then transfer the MTB, NaOH lines, and the sample dilution lines to the
EDTA solution container for 10 min. All liquid lines are then finally washed
with distilled water for 15 min before shutting down the analyzer. The sample
line may be conveniently washed during this operation by shutting off the
turntable when the sample probe is in the wash position. All liquid lines
should be left filled with water after the system has been washed if daily
use is anticipated. If, however, the system is idle for 1 week or more,
all lines must be drained and dried. During analysis a coating will slowly
build up on the flow cell windows which is not completely removed by the
EDTA wash. This buildup is indicated by a loss in colorimeter sensitivity
and may be removed by washing the cell with 1 N HGl followed by an acetone
and then a water wash.
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8. Calibration
8.1. Fa.eh Volume Sampler; The high volume air sampler shall be cali-
orated as specified in "Appendix B - Reference Method for the Determination
of Suspended Particulates in the Atmosphere (High Volume Method)."Z'
8.2. Technicon II Autoanalyzer
8.2*1. Flow Rates; The flow rates in the Autoanalyzer system
should be checked when the system is originally set up. It should also be
checked when any system substitutions are made. Disconnect the specific .
line as it leaves the pump and insert the line in a 10-ml graduated cylinder.
Operate the pump for 2 min. If the flow rate is in error by more than 5%,
change the pump tubing and recheck the flow.
The flow rates indicated in Figure 1 page 5 will produce the recom-
mended reagent ratios. Minor variations in flow can be tolerated as long
as they are constant, since they will be corrected for in the calibration
procedure.
8.2.2. Colorimeter Wavelength; The uncomplexed MTB at a pH of
12.4 has a maximum absorbance at 460 nm. The colorimeter wavelength accuracy
should be checked prior to use and annually thereafter. Maximum transmis-
sion of the filter should occur at 460 + 15 nm.
8*2.3. Concentration Standards; Dilute 50 ml of stock sulfate
solution containing 1,000 jxg S04=/ral to 500 ml with distilled water. This
intermediate sulfate solution contains 100 ^g S0^~/ml. If a linearizer
is used, pipette 15, 35, 50, 65, 80, and 95 ml of 100 ^g S04.-/ml solution
into separate 100-ml volumetric flasks and dilute to the mark with distilled
water. These solutions contain 15, 35, 50, 65, 80, and 95 M8 S0^~/ml,
respectively. If a linearizer is not used, pipette 5, 10, 10, 15, 20, 50,
60, and 75 ml of the 100 /ig S04=7ml solution into 100, 100, 50, 50, 100,
100, and 100 ml volumetric flasks and dilute to the mark with distilled
water. The solutions contain 5, 10, 20, 30, 40, 50, 60, and 75 ^tg S04~/ml,
respectively.
8.2.4. Autoanalyzer Start Up; Start up the analyzer and start
reagents flowing through the system. The sample in the flow cell must be
free of bubbles during operation. Refer to manufacturer's instructions for
general operating procedures. Set the sampling rate at 40, the wash time
at 12 sec, the range switch at 100, and the decimal switch at 000.
Operate the instrument until a stable baseline is obtained. This
normally requires a minimum of 30 rain. The turntable is loaded with dupli-
cate stanc'^rds in the following sequence; 0, 100, 0, followed by low to
high sulfate standards.
-------
8*2*4.1. Operation with Linear!zer: The linearizer switch
is set in the direct mode and the recorder is zeroed using the baseline
control and water blanks and spanned to 100% full scale using the standard
calibration control and a 100 ^g/ral'standard. The recorder is rezeroed when
the second set of water blanks reaches steady state. The linearizer is then
switched to the linear mode. When the 15 jig/ml standard reaches steady state,
adjust the 0 to 20 calibration control until the concentration indicator
reads 15 and activate the printer. The second 15 /ng/ml standard should validate
the setting by indicating the correct concentration. As the 35 /^tg/ml standard
reaches steady state, adjust the 20 to 40 calibration control until 35 jig/ml
is indicated. Continue to adjust each calibration control using the standard
which lies within its range until all calibration controls have been set.
The calibration controls are locked in position after they have been adjusted.
The adjustment of the linearizer needs to be repeated only when changing
lots of MTB or when a standard varies more than 3 ^g/ml from its true value.
8.2.4*2. Operation Without Linearizer; The recorder is
zeroed using the baseline control and water blanks and spanned to 100% full
scale using the standard calibration control and the 100 ^g/ml standard.
The recorder is rezeroed when the second set of water blanks reaches steady
state. The remaining standards are then processed and the recorded values
compared with their true values. The differences should be less than 3 /ng/ml.
Repeat span and zero adjustments if required. If acceptable readings cannot
be obtained, check analyzer operation, flow rates, and reagent concentrations
to locate problem.
When operating the automatic analyzer, air bubbles should
not be allowed to enter the ion-exchange column. If air bubbles become trapped,
the ion-exchange column should be replaced with a new column. A broadening
of the colorimeter output with a corresponding loss in peak height usually
indicates a performance decay in the pump tubing. At the first indication
of peak broadening the pump tubing should be replaced. Pump tubing normally
is good for at least 190 hr of operation.
8.2.5. 100% Adjustment; The full range of the recorder is used,
from 0 to 100%.
8.2.6. Baseline Adjustment; The baseline is adjust to zero at
the beginning and after every 10th sample using a distilled water blank.
8.2.7. Calibration Standards; Standards are run at the beginning
and end of each day. If at the end of the day, the standards vary more than
3 jug/ml from their true value, the run is considered invalid and must be
repeated.
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8.2.8. Assay of Methylthmol Blue; The purity of commercial MTB
may vary considerably. It is, therefore, necessary to determine the barium
equivalency for each lot of MTB using the following procedure*
To 0.164 g of MTB in a 500-ml volumetric flask, add successively
75 ml of 0.0086 M barium chloride solution (6.2.14.), 4 ml of 1.0 N hydro-
chloric acid (6.2.13.), and make to 500 ml with 95% ethanol.
Pipette 2, 3, 4, 5, 6, 8, 10, 12, 14, 16, 17, 18, 19, and 20 ml
of 1,000 /^g S04=/ml solution (6.12.18.) into separate 100-ml volumetric
flasks and dilute to the mark with distilled water. Oiese solutions contain
20, 30, 40, 50, 60, 80, 100, 120, 140, 160, 170, 180, 190, and 200 fjig
S04~/ml, respectively.
Start up the analyzer using the above MTB solution in place of
the normal MTB solution. Operate the analyzer until a stable baseline is
obtained.
Span the analyzer using the 200 //g S04~/ml solution and proceed
to analyze in triplicate all of the above sulfate solutions. The analysis
should be conducted with the linearizer in the direct mode. Plot the data,
micrograms S04=/ml versus peak height, on linear graph paper. The plot will
consist of three intersecting straight lines as shown in Figure 3. The inter-
section of the first and second portions of the plot (1) indicates the sulfate
concentration required to react with the excess barium. The intersection
of the second and third portions of the plot (2) indicates the sulfate concen-
tration required to react with the complexed barium. Determine these two
intersects and calculate the purity and amount of MTB to be used for reagent
preparation as described in 9.1. and 9.2.
9. Calculations
[Mg S04/ml(p) - Oug S04/ml(c) + ^ug S04/ml(b))] x 50 x 12
MS
where :
MS SO^/ml, N = printout for sample (7.2.2.1.)
ug S04=/ml/c) = color correction (7.2.2.1.)
jtig S04=/ml/[3) = blank correction. This is the S04= content
of the filter reduced to g/ral for the mean 3/4 in.
x 8 in. filter strip (6.1.1*2.).
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0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190
SO4=/ml
Figure 3 - Plot of MTB Assay
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50 = correction to toal volume of the sample (7.21.1).
12 = correction to entire filter SC^ content (9 -f
3/4) (7.2.1.).
V = total volume of air through filter, nH (8.1.).
9.1. Calculation of MTB Purity:
[>g S04/ml(2) - MS S0£/»l(l)] FL x C x 866.73
% Purity = - x 10°
W x F2 x 2
where:
S04~/ml/2} = jug/ml reading from second intersection point 8.2.8
/tig/ml reading from first intersection point 8.2.8.
F-^ = flow rate in ml/min for sample line (normally 0.32)
C = molar concentration of stock solution (normally 1.041 x 10"*)
866.74 = molecular weight of MTB
W = weight of MTB in mg
F£ — flow rate in ml/min for MTB line (normally 0.7)
2 = value to calculate MTB concentration on basis of equivalents/liter.
9.2. Calculation of Weight of MTB;
Weight of material for analysis = 0.164 x 100
7, Purity from (9.1.)
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10. References
Lazrus, A. L., K. C. Hill, and J. P. Lodge, "A New Colorimetric
Microdetermination fo Sulfate Ion." Presented at the Technicon Sym-
posium, "Automation in Analytical Chemistry," New York, New York,
September 8, 1965.
"Appendix B - Reference Method for the Determination of Suspended
Particulates in the Atmosphere (High Volume Method)," Federal
Register, 36(84):8191-8194, April 30, 1971.
ASTM Standards (Water, Atmospheric Analysis), Part 23, October 1969
(p. 225).
"Guidelines for Development of a Quality Assurance Program - Reference
Method for the Determination of Suspended Particulates in the Atmos-
phere (High Volume Method)," EPA Environmental Monitoring Series,
EPA-R4-73-028b, June 1973.
ASTM Manual on Quality Control of Methods, Special Technical Pub-
lication 15-C, January 1951. Obtainable from ASTM, 1916 Race Street,
Philadelphia, Pennsylvania 19103.
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APPENDIX F
Protocol for Ion Chromatographic Analyses of Sulfate and Nitrate
1. Equipment
1.1 lon-Chromatograph. Dionex System 10 Ion Chromatograph, Dionex Corp.,
1228 Titan Way, Sunnyvale, CA 9^087.
1.2 Varian A-25 Recorder and Spectra-Physics Autolab Minigrator Model
23000-010. (Spectra Physics, 2905 Stender Way, Santa Clara, CA 95051)
1.3 Containers. To hold extraction solution and subsequent storage of
samples, U oz. polypropylene containers with plastic screw-caps.
l.U Filters (extraction). 0.^5 y disposable filter unit (Swinnex-25
Filter Unit, Millipore , or equivalent).
1.5 Syringes. 12 cc disposable syringes, without needle, graduations
0.2 cc. (Monoject Sterile Disposable Syringe, Cat. No. 512S, or
equivalent)
2. Reagents
2.1 Deionized, filtered water. (D.F. H20 for all reagents and suppressor
column rinse.) To minimize introduction of background ions into the
system, the water should be deionized to a resistance of approximately
15 megohms, or conductivity of 0.1 to 1.0 micromho/cm. The water
should be free of particles larger than 0.20 ym to avoid the accumula-
tion of residue or debris in the ion-exchange beads or flow system.
Fill reservoir labelled "H^O" in the chromatograph.
* When filling reservoirs, avoid air bubbles which may cause pumps to lose
their prime - see instruction manual for this procedure.
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2.2 Eluant. Prepare 0.003 M NaHC03 - 0.002U M Wa2C03 solution as
follows: In a 2-liter volumetric flask, dissolve 1.008 g NaHC03
(sodium bicarbonate, MCB, Cat. No. SX320 or equivalent) and
1.0175 gNa2C03 (sodium carbonate, MCB, Cat. No. SX395-CB705 or
equivalent) with deionized filtered water prepared as in 2.1
above. Invert gently to dissolve, make to the mark with deionized
water, mix. Transfer to the eluant reservoir labelled "EI" or
%
"E2" in the chromatograph. Add an additional 2 liters to make
a total of 1* liters, and mix well.
2.3 Regenerant. Prepare 1 N E2SO^ as follows: Into a 2 liter volumetric
flask containing approximately 1 liter of deionized filtered water,
introduce 111 ml of concentrated sulfuric acid, mix, cool. Make
to the mark with deionized water, mix. Fill reservoir labelled
"Regenerant" in the chromatograph. Add an additional 2 liters
to make a total of U liters, and mix well.
2.k Stock Standard Sulfate Solution (1000 yg sulfate/ml). Dry (NHtt)2SOtt
(ammonium sulfate, NBS certified) powder at 105°C for U hours, cool
in a desiccator. Dissolve 1.376 g of the dried ammonium sulfate
in deionized water and dilute to 1 liter.
2.5 Stock Standard Nitrate Solution (1000 pg nitrate/ml). Dry KN03
(potassium nitrate, NBS certified) powder at 105°C for k hours,
cool in a desiccator. Dissolve 1.631 g of the dried potassium
nitrate in deionized filtered water and dilute to 1 liter.
* When filling reservoirs, avoid air bubbles which may cause pumps to lose
their prime - see instruction manual for this procedure.
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2.6 Nitrate-Sulfate Working Standards. Prepare working standards of
0, 5, 10, 20, 1*0 160 pg/ml nitrate and sulfate concentrations.
To obtain the best accuracy and precision, weigh out the required
amounts of stock standards into small beakers, and then transfer
the contents to Class A volumetric flasks. The samples are then
bracketed by at least four standards during analysis. Samples
of higher concentration (outside the 10 ymho range) are set aside,
diluted, and analyzed at a later time.
Working Standard ml or gms of Nitrate ml or gms of Sulfate
yg/ml Hitrate-Sulfate Stock Std. Added Stock Std. Added
0
5
10
20
160
0
0.50
1.00
2.00
16.00
0
0.50
1.00
2.00
16.00
In each case, after addition of both stock standards to a 100 ml
Class A volumetric flask, add sufficient double distilled water
to the mark.
3. Analytical Procedure (Note: Read the chromatograph and integrator
instruction manuals before proceeding).
3.1 Integrator-Recorder Operation. If the range of the sample is known
beforehand (e.g., 0 to 80 yg/ml), it is possible to optimize the
recorder response by adjusting the integrator attenuation and
recorder span. For general operation on the 10 ymho to scale, so
that the recorder response corresponds 1 to 1 with the Dionex meter,
the controls are set as below.
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Varian A-25 Recorder
Span: 1.0 volt. Adjust the recorder zero and span so that they
coincide with the Dionex meter readings.
Chart Speed: 10 inches per hour, when the 3 x 500 mm anion column
is used.
Minigrator Model 23000-010
The most important parameters are set as below:
Peak Width (PW) = 99
Slope Sensitivity (SS) = 99999
Baseline (BL) =1.0
Trailing Peak (TP) = 1
The following parameters are inactivated: MA, SP, PL, BI, 62, and
T2. TI is set at a time which eliminates early peaks, just prior
to elution of the nitrate curve. (Determine by experience)
3.2 Put the toggle switch on the front panel of the chromatograph
in the LOAD position; using a syringe, inject 2 ml of sample solution
into the injection port. Leave the syringe in place during chroma-
tography.
3.3 Using the OFFSET COARSE or FINE knobs, adjust the indicator needle
on the SPECIFIC CONDUCTANCE meter to 0.0.
3.U Flip the toggle switch to the INJECT position, at the same time
start the integrator or strip chart. After 15-30 seconds, flip
the toggle switch back into the LOAD position.
3.5 Record the sample I.D. on the chart.
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3.6 After the run is completed, rinse the sample loop with 3 ml of
deionized filtered water with the toggle switch still in the
LOAD position.
3.T Inject the next sample as described in Sections 3.2 through 3.6.
Note: The system will use approximately k liters of eluant per day.
U. Chromatograph Start-Up (Review lon-Chromatograph Instrument Manual)
U.I Using the regulator on a dry air or nitrogen compressed gas cylinder,
adjust the pressure to 90-100 psi for the air actuated valves in
the chromatograph. Flip the toggle labelled AIR, on the front
panel of the chromatograph, to the ON position.
U.2 Flip the toggle labelled POWER to the ON position.
U.3 Place the toggle labelled FLUSH down.
INJECT
U.U Place the toggle labelled 0/. down.
Ei
U.5 Place the toggle labelled l up.
WATER
k.6 Place the toggle labelled E2 up if EX is empty.
U.7 Place the toggle labelled E2 down if reservoir EX is full.
H.8 Place the toggle labelled ANALYT up.
U.9 Place the toggle labelled SUPPRESS up.
U.10 Flip the toggle labelled PUMP to the ON position. Adjust the
vernier dial on the front pump so that the flow rate is appropriate,
e.g. , 2.5 ml min. (The flow ate may be checked by disconnecting the
output tubing from the suppressor column and placing the tubing in
a graduated cylinder). Allow the system to run for 30 minutes
before beginning the integrator calibration, or until the baseline
drift is reasonably stable. Check for leaks in the tubing connections.
Wear safety glasses when opening the column door. Check reservoir
levels.
- 18U -
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U.ll Turn MODE switch to LIN.
H.12 Turn yMHO FULL SCALE to 10.
U.13 Set SPECIFIC CONDUCTANCE needle to 5.0 or 10.00 with the OFFSET
COARSE and FINE knobs. (Allow sufficient positive baseline to
account for any negative drift).
5- Standards and Calibration
5-1 Inject 3 ml of each of the standards described in paragraph 2.6.
Record -the reading by automatic integration and by measuring the
recorder trace (chromatogram) peak height.
5.2 Calculate regression lines separately for nitrate and sulfate
plotting recorder response versus concentration.
6. Regeneration of Suppressor Column
6.1 At the end of each day's run, the suppressor column required
regeneration as indicated by a color change in the column resin
bed from tan to whitish tan, or by a swift rise in the conductance.
6.2 On the chromatograph, make the following settings:
6.2.1 Flip toggle switch labelled PUMPS to the OFF position. Set
the switch labelled MODE to ZERO.
6.2.2 Flip toggle switch labelled SUPPRESS to the down position.
Check the liquid levels in the regenerant and "H20" reservoirs.
6.2.3 Set TIME MIN indicators to 10 on REG side and 50 on RIN side.
6.2.^ Depress the green button labelled START, the rear pump should
begin pumping. Set the vernier on the rear pump to approximately
90.
6.2.5 The cycle of regeneration is now automatic. At the end of
the cycle, the pump will stop and the suppressor column will
be tan colored. The cycle may be stopped prematurely by
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depressing the red colored button labelled RESET.
T. Chromatograph Shut Dovn
T.I Flip the toggle switch labelled PUMP to the OFF position.
7.2 If the regeneration cycle is in process, and premature termination
is necessary, depress the red button labelled RESET.
7.3 Make sure the integrator is off (LINE button has been depressed
and indicator lights are off).
7.U Flip toggle switch labelled POWER to the OFF position.
7.5 Flip AIR toggle switch to the OFF position.
7.6 Turn off regulator on compressed air or nitrogen cylinder.
7-7 Protect the integrator from dust using a plastic cover.
7.8 If the chromatograph is to be shut down for a long period of time
(e.g., 2 months) rinse both columns with distilled water beforehand.
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APPENDIX G
Protocol for Extraction of Organics from Aqueous Extracts of Atmospheric
Partieulates for Use in Interference Studies of Sulfate Methods
Objective
To extract the .organics from aqueous extracts from atmospheric particulate
matter -without co-extraction of sulfate.
X1
Procedure
About 2kOO ml of an aqueous extract obtained from extraction at 85-100°C
of 60 loaded 8 x 10" hi-vol filter samples was filtered through Whatman #2
filter paper. The filtrate was transferred into three 2 liter beakers and
evaporated on a steam bath to about 0.6 liter (total). This was acidified
with HC1 and the 0.6 liter extracted with three 100 ml portions of 1:1 v/v
butanol-chloroform. The aqueous phase was evaporated to near dryness and
extracted with 100 ml of butanol-chloroform. The UOO ml of organic extract
was washed twice with 100 ml distilled water. No sulfate could be detected
in the wash water (tested with aminoperimidine). The organic solvent was
then evaporated to dryness on the steam bath. The brown, resinous residue
was dissolved in 20 ml water containing 0.5 ml of k N NHi+OB in a petri dish.
The petri dish was heated for 5 minutes to evaporate excess ammonia. The
solution was diluted and filtered with washing into a 250 ml volumetric
flask and made up to 250 ml with distilled water.
Result
The pH of the solution so obtained was 6.5 and the color intensity about 2
at \ = UOO nm. Comparison of this absorbance with that of the remaining
yellow aqueous solution indicated 6U% extraction of the chromophoric organics.
The colored organics in the remaining solution was hydrophilic at all pH
values and could not be easily extracted or freed of sulfate.
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
NO.
EPA 60Q/4-79-D?R
3. RECIPIENT'S ACCESSIOWNO.
c. I.E A\O SUBTITLE
IMPROVEMENT AND EVALUATION OF METHODS FOR SULFATE
ANALYSIS
5. REPORT DATE
April 1979
6. PERFORMING ORGANIZATION CODE
AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
B.
E.
R. Appel,
L. Kothy,
E. M. Hoffer, M. Haik,
and J. J. Wesolowski
W. Wehermeister,
9, PERFORMING ORGANIZATION NAME AND ADDRESS
Air and Industrial Hygiene Laboratory Section
California Department of Health
2151 Berkeley Way
Berkeley. California 94704
10. PROGRAM ELEMENT NO.
1AD883
11. CONTRACT/GRANT NO.
Grant R-805-447-1
12. SPONSORING AGENCY NAME AND ADDRESS
Office of Research and Development
Environmental Monitoring and Support Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final Report 1977-78
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
A simpler and faster procedure for the manual turbidimetric analysis of sulfate
has been developed and evaluated. This method as well as a turbidimetric procedure
using SulfaVer , automated methyl thymol blue (MTB) procedures for analysis in the
0-100 yg/ml and 0-10 yg sulfate/ml ranges, and the Dionex Ion Chromatograph were
evaluated for accuracy, precision, working range, interference effects, and degree of
agreement using atmospheric samples. Using EPA sulfate audit strips, all methods
showed accuracies within 8% of the accepted value, and coefficients of variation with
atmospheric samples of <_ 6%. Colloidal clay and yellow, water soluble organics
isolated from atmospheric samples caused interference with all methods. All the
methods studied provide reliable analyses for 24-hour hi-vol filter samples. The
automated MTB method, modified for use in the 0-10 yg/ml range as suggested by Colovos.
offers excellent potential for analysis of low volume samples such as those provided
by a dichotomous sampler network.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
Air Pollution and Control
Environment
Air Monitoring
Measurement Methods
Sulfates
68A
43F
8. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (ThisReport)
IIMPI
21. NO. OF PAGES
197
20. SECURITY CLASS (Thispage)
22. PRICE
EPA Form 2220-1 (9-73)
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