903978006
U.S. ENVIRONMENTAL PROTECTION AGENCY
MIDDLE ATLANTIC REGION-III 6th and Walnut Streets, Philadelphia, Pennsylvania 19106
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EPA 903/9-78-006
ANALYSIS OF SULFUR IN FUEL OILS BY
ENERGY-DISPERSIVE X-RAY FLUORESCENCE
January 1978
Technical Paper No. 15
Annapolis Field Office
Region III
Environmental Protection Agency
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Annapolis Field Office
Region III
Environmental Protection Agency
ANALYSIS OF SULFUR IN FUEL OILS BY
ENERGY-DISPERSIVE X-RAY FLUORESCENCE
E. R. Trovato
J. W. Barron
J. L. Slayton
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DISCLAIMER
The mention of trade names or commercial products in this report
is for illustration purposes and does not constitute endorsement or
recommendation by the U.S. Environmental Protection Agency.
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INTRODUCTION
Sulfur oxides have long been recognized as significant air
pollutants. With increased usage of sulfur containing fuels, an
increase in atmospheric sulfur dioxide content will become an
ever more important problem. Legislation has been passed governing
the allowable levels of sulfur in fuels in an attempt to control
this source of air pollution.
Energy-dispersive x-ray fluorescence (EDXRF) can provide a
rapid, non-destructive method of analysis of sulfur in fuel oils.
Because the EDXRF system is automated and minimal sample preparation
procedures are involved, a reduction in the time and cost of
analysis is possible.
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EXPERIMENTAL
Materials
Sulfur standards of: 2.14, 1.05, 0.268, and 0.211 weight
percent sulfur in fuel oil were obtained from the National
Bureau of Standards. In addition, sulfur standards prepared
by commercial sources were obtained with concentrations in
weight percent sulfur of: 2.02, 1.06, and 0.49. Actual
samples analyzed by wavelength-dispersive x-ray fluorescence
with the following weight percent sulfur concentrations were
also analyzed: 2.95, 2.10, 2.05, 2.00, 1.61, and 0.33.
Zinc, barium, and lead standards were prepared from Conostan
Metallic-Organic standards.
Equipment
A Finnigan 900 Series energy dispersive x-ray fluorescence
spectrometer and data system were used for all EDXRF analyses.
Procedure
The determination of sulfur in fuel oils follows the procedure
outlined-in ASTM D2622-671: Standard Method of Test for Sulfur
in Petroleum Products (X-Ray Spectrographic Method) with
minor changes in the procedure to accommodate the energy
dispersive equipment. A brief outline of the procedure follows:
a. Place the sample in an open cell sample cup over which
0.25-mil Mylar film has been stretched and attached
with a. snap-on ring. Attach microporous film to the
open-end of the sample cup to prohibit the oil
from escaping.
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b. Place the samples in the x-ray beam, apply vacuum,
and allow the atmosphere in the x-ray chamber to
come to equilibrium. Instrument operating conditions
are found in Table III.
c. Determine the intensity of the SK^ peak at 2.307 Kev
and make background measurements adjacent to the peak.
d. If the sample contains interfering elements in
concentrations greater than those listed in ASTM
D2622-67, dilute the sample by weight with white oil.
Calibration
a. Determine the net SK-, intensity for all standards
and samples.
b. Determine the weight percent sulfur by ratio against
the 2.14 weight percent sulfur standard reference
material using net intensities or by comparison to a
calibration curve of sulfur net intensity vs. concentration.
c. Measure a sensitivity standard at frequent intervals
and determine the net counting rate for each sample.
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RESULTS AND DISCUSSION
Commercially obtained standards, NBS standards, and previously
analyzed field samples were analyzed by energy dispersive x-ray
fluorescence. The accuracy results shown in Table I and precision
results shown in Table II, indicate the high degree of precision and
accuracy obtainable by this method of analysis. The average recovery
was 97# (Table I) and a plot (Figure I) of found weight percent sul-
fur vs. known weight percent sulfur gives a correlation coefficient
of 0.999. A paried-t test applied to the data indicates that there
is no difference between the found and known values at a 95/5 confi-
dence level. An average standard deviation of 0.02 weight percent
sulfur was found over the 0.16 to 2.00 weight percent sulfur range.
A plot of the standard calibration curve (Figure II) is linear with
a correlation coefficient of 0.9997, further facilitating analysis by
this method.
The minimum detectable amount2, defined as 3x(intensity of the
background)1/2, is 0.11 weight percent sulfur; this is below the
majority of legislated limits of sulfur concentration in fuel oil in
the United States3.
The analysis of fuel oil samples by energy-dispersive x-ray
fluorescence is accurate and precise, requires minimal sample
preparation, and is non-destructive. It also simultaneously deter-
mines sulfur and its interfering elements, phosphorus, zinc, barium,
calcium, and chlorine. These factors combine to produce an overall
increase in the efficiency of analysis of sulfur in fuel oils.
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TABLE I
Comparison of Sulfur Results Found by Classical and EDXRF Methods
Date of
Analysis
10-28-75
8-12-76
2-11-77
2-14-77
4-27-77
Origin
Field Sample
Field Sample
Field Sample
Secondary Std.
Field Sample
Field Sample
Secondary Std.
Field Sample
Field Sample
Field Sample
Field Sample
Secondary Std.
NBS
Secondary Std.
NBS
NBS
NBS
NBS
Secondary Std.
NBS
NBS
NBS
Secondary Std,
NBS
correlation coefficient = .999
Classical
wt. % S
2.95
2.10
2.05
2.02
2.00
1.61
1.06
2.94
2.10
2.00
1.61
1.06
1.05
0.49
0.268
0.211
1.05
0.211
1.06
1.05
1.05
0.268
0.24
0.211
EDXRF
wt. % S
2.98
2.07
2.05
1.94
2.04
1.68
0.99
3.04
2.13
2.04
1.67
1.01
1.04
0.48
0.264
0.206
1.02
0.155
1.00
1.06
1.03
0.231
0.22
0.192
% R*_
101.0
98.6
100.0
96.0
102.0
104.3
93.4
103.4
101.4
102.0
103.7
95.3
99.0
98.0
98.5
97.6
97.1
73.4
94.3
101.0
98.1
86.2
91.7
91.0
mean
s
97. %
6.7%
t-statistic = .540
degrees of freedom
= 23
*R - Recovered
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Figure I: Plot of Found Weight Percent Sulfur vs Known Weight Percent Sulfur
30!
Found
wt. % S
r = .9990
m = 1.028
b = -0.04027
zir
Known wt. % S
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TABLE II
Results of Duplicate Analyses of Field Samples
Duplicate I
wt. % S
.16
.16
.16
.16
.16
Duplicate II
wt. % S
.17
.17
.19
.21
.17
s = .02% S
difference
Toi
.01
.03
.05
.01
0.3-1.0%
.72
.96
.99
.93
.59
.44
.72
.98
.98
.91
.58
.44
s = .01% S
0
.02
.01
.02
.01
0
> 1.0%
99
03
04
05
74
09
.96
1.63
92
01
00
04
74
08
94
63
.07
.02
.04
.01
0
.01
.02
0
s = .02% S
s = (E(d2) /2k) *
where: s = standard deviation
d = difference between duplicates
k = number of samples
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TABLE III
Instrument Operating Conditions
Date
of Voltage Amperage Time Collimator
Analysis Kv ma sec Path Filter diameter mm
10-28-75 10 4 500 vacuum none 1
8-12-76 10 1 500 vacuum none 6
2-11-77 10 0.8 500 vacuum none 6
2-14-77 10 0.8 1000 vacuum none 6
4-27-77 10 0.8 1000 vacuum none 6
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-igure II: Plot of SKa Net Intensity vs Weight Percent Sulfur
;
300
Net I
(c/sec)
200
100
,
°
/
/
j
i
j
•
/'
/
/
/
r = .9997
m = 144.99
/ b = -5.246
/
/
t
/
/
/
y
/
/
f
/
/
/
/
/
••^ | - -- f » ^
J .5 1.0 1.5 2.0
Weight % Sulfur
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REFERENCES
1. ASTM D2622-67, ASTM Standards on Petroleum Products and Lubricants,
ASTM Committee D-2, September 1967
2. Bertin, Eugene P., Principles and Practice of X-Ray Spectrometric
Analysis, Plenum Press, New York, 1975
3. Martin, Werner and Stern, Arthur C., The World's Air Quality
Management Standards, Volume II: The Air Quality
Management Standards of the United States, U.S.
Environmental Protection Agency, Office of Research
and Development, Wash., D.C., 1974, pg. 113-124
4. U.S. Environmental Protection Agency, Office of Water Programs
Operations, National Training and Operational Technology
Center, Participant's Handbook for the Drinking Water
Chemical Laboratory Certification Course, pg. E9-20
ACKNOWLEDGEMENTS
We would like to thank: Dr. Jungers, EPA, RTF; Mr. Al Curry,
Aerospace Fuels Lab; Mr. Mae Dill, AFB, Tampa, Fla.; and Mr. Al Kewing,
Mobil Oil, Paulsboro, N.J. for providing analyzed samples and
commercial standards utilized.
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA 903/9-78-006
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Analysis of Sulfur in Fuel Oils by Energy Dispersive
X-ray Fluorescence
5. REPORT DATE
January 1978
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
E. R. Trovato, J. W. Barron, J. L. Slayton
8. PERFORMING ORGANIZATION REPORT NO.
Technical Paper 13
10. PROGRAM ELEMENT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Annapolis Field Office, Region III
U.S. Environmental Protection Agency
Annapolis Science Center
Annapolis, Maryland 21/401
2BD144
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
Same
13. TYPE OF REPORT AND PERIOD COVERED
In House; Final
14. SPONSORING AGENCY CODE
EPA/903/00
15. SUPPLEMENTARY NOTES
16. ABSTRACT
Energy dispersive x-ray fluorescence was used to analyze for sulfur in oil in
commercially prepared standards, NBS standards and laboratory samples. The
technique of energy dispersive x-ray fluorescence for sulfur was found to be
accurate, precise, and required minimal sample preparation. In addition it
was non-destructive, and enabled the simultaneous determination of sulfur and
its interfering elements: phosphorus; zinc; barium; calcium; and chlorine.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
X-ray Fluorescence Sulfur Analysis
Sulfur Determination Fuel Oil
Energy-dispersive X-ray
Fluorescence Sulfur
Analysis
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