EPA Document #: EPA/600/R-06/115
METHOD 200.5 DETERMINATION OF TRACE ELEMENTS IN DRINKING
WATER BY AXIALLY VIEWED INDUCTIVELY COUPLED
PLASMA - ATOMIC EMISSION SPECTROMETRY
Revision 4.2
October 2003
Theodore D. Martin
NATIONAL EXPOSURE RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U. S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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METHOD 200.5
DETERMINATION OF TRACE ELEMENTS IN DRINKING WATER BY AXIALLY
VIEWED INDUCTIVELY COUPLED PLASMA-ATOMIC EMISSION
SPECTROMETRY
1.0 SCOPE AND APPLICATION
1.1 Axially viewed inductively coupled plasma-atomic emission spectrometry
(AVICP-AES) is used to determine trace elements, as well as water matrix elements,
in drinking water and drinking water supplies. This method is applicable to the
following analytes:
Chemical Abstract Services
Analyte Abbreviation Registry Numbers (CASRN)
Aluminum
Antimony*
Arsenic*
Barium*
Beryllium*
Boron
Cadmium*
Calcium
Chromium*
Copper*
Iron
Lead*
Magnesium
Manganese
Nickel
Selenium*
Silica
Silver
Sodium
Tin
Vanadium
Zinc
(Al)
(Sb)
(As)
(Ba)
(Be)
(B)
(Cd)
(Ca)
(Cr)
(Cu)
(Fe)
(Pb)
(Mg)
(Mn)
(Ni)
(Se)
(Si02)
(Ag)
(Na)
(Sn)
(V)
(Zn)
7429-90-5
7440-36-0
7440-38-2
7440-39-3
7440-41-7
7440-42-8
7440-43-9
7440-70-2
7440-47-3
7440-50-8
7439-89-6
7439-92-1
7439-95.4
7439-96-5
7440-02-0
7782-49-2
7631-86-9
7440-22-4
7440-23-5
7440-31-5
7440-62-2
7440-66-6
* Designated primary drinking water contaminant.
1.2 For reference where this method is approved for use in compliance monitoring
program (e.g., Safe Drinking Water Act [SOWA]) consult both the appropriate
sections of the Code of Federal Regulation (40 CFR Part 141 § 141.23) and the
latest Federal Register announcements.
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1.3 This method provides a specific procedure utilizing axially-viewed plasma atomic
emission signals generated only by pneumatic nebulization for the analysis of all
analytes. Some AVICP-AES instruments are so configured that the emitted signal
can also be viewed alternately or simultaneously in a radial manner. Radially-
viewed signals for the determination of drinking water matrix elements (Ca, Mg and
Na) and silica are acceptable. The Ca and Mg data can be used in the calculation of
hardness.
1.4 When viewing sodium emission from the axial configuration, the ratio of signal
intensity to analyte concentration is not a linear response. Therefore, sodium should
be calibrated using multiple standard solutions of increasing concentration to
properly define the response ratio at various levels of concentration (see Sect. 7.8.2).
1.5 For drinking water compliance monitoring, a "total" element determination
(dissolved + suspended fractions) is required. When the measured turbidity on an
acid preserved sample is < 1 NTU, direct analysis, without sample digestion, is
permitted with the use of some approved spectrochemical methods. However, when
using this method, all samples are digested and preconcentrated prior to analysis
using the total recoverable digestion(1) step described in Section 11.1.
Preconcentrating the sample prior to analysis increases analytical sensitivity for
meeting the method detection limit (MDL) requirements given in Section 1.12.
Thus, when using this method, the need to measure sample turbidity prior to metal
analysis is eliminated.
1.6 Operative matrix effects can occur from elevated dissolved solids. Using this
technique, matrix effects have been observed when the concentration of calcium
and/or the combined concentrations of the matrix elements (Ca, Mg, and Na) and
silica exceed 125 mg/L and 250 mg/L, respectively. To verify that a matrix effect is
not operative, an LFM (see Sect. 9.4) must be analyzed when a primary contaminant
(see Sect. 1.1) concentration exceeds 80% of the established maximum contaminant
level (MCL) or action level. If the absence of a matrix interference can not be
verified, the sample must be analyzed by method of standard additions (MSA; see
Sect. 11.3) or another approved method (see Sect. 1.7 for special requirements for
lead).
1.7 When determining lead by this method, the instrument must be capable of analyzing
silica as well. Levels of silica that exceed 30 mg/L, when preconcentrated 2X,
cause a suppressive effect on lead determinations. For samples containing silica
above 30 mg/L and lead concentrations > 10 |ig/L, lead must be determined by
method of standard additions (MSA; see Sect. 11.3) or by another approved
compliance monitoring method. If the laboratory can not determine silica when
using this method, this method can not be used for compliance monitoring of lead.
1.8 When determining boron and silica, only plastic or PTFE labware should be used
from time of sample collection to completion of analysis. In this method, glassware
is specifically avoided and only the use of metal-free plastic labware is
recommended. Borosilicate glass should be avoided to prevent contamination of
these analytes.
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1.9 The total recoverable sample digestion procedure given in Section 11.1 is suitable
for the determination of silver in aqueous samples containing concentrations up to
0.1 mg/L. Also, samples prepared using the procedure may be analyzed for thallium
using EPA Method 200.9(2).
1.10 Compliance monitoring data for metal contaminants are normally reported in units
of mg/L; however, the data for the total recoverable analytes in this method are
noted in units of |ig/L. This difference is done to reduce or eliminate the listing of
non-significant zeros. When data are reported for compliance monitoring, the data
should be reported in the same units used to express the established MCL and to the
appropriate numerical level of significance.
1.11 MDLs for trace elements and linear ranges for the drinking water matrix elements
will vary with the wavelength selected and the spectrometer configuration and
operating conditions. Table 4 provides determined MDLs for the listed wavelengths
utilizing the instrument operating conditions given in Table 3. These values are
provided for comparative purposes for user self-evaluation when completing the
mandatory initial demonstration of performance. Meeting the exact same limits
listed in Table 4 is not necessarily a requirement for the use of this method. Users
of this method must document and have on file the required initial demonstration
performance data described in Section 9.2 prior to using the method for analysis
(see Sect. 1.12).
1.12 Users of this method for the purpose of SDWA compliance monitoring must achieve
and document MDLs for As, Be, Cd, Sb, Se, and Pb that are < a value of 1/5 their
respective MCL or action level.
2.0 SUMMARY OF METHOD
2.1 A 50 mL aliquot of a well-mixed, non-filtered, acid preserved aqueous sample is
accurately transferred to a clean 50-mL plastic disposable digestion tube containing
a mixture of nitric and hydrochloric acids. The aliquot is heated to 95 °C (± 2 °C),
evaporated to approximately 25 mL, covered with a ribbed plastic watch glass and
subjected to total recoverable solubilization with gentle refluxing for 30 minutes.
The sample is allowed to cool and diluted to 25 mL with reagent water to effect a
2X preconcentration. The sample is capped, mixed and now ready for analysis (The
time required to complete the sample preparation step is approximately 2.5 hours).
2.2 The analytical determinative step described in this method involves multi-elemental
determinations by AVICP-AES using sequential or simultaneous instruments. The
instruments measure characteristic atomic-line emission spectra by optical
spectrometry. Standard and sample solutions are nebulized by pneumatic
nebulization and the resulting aerosol is transported by argon carrier-gas to the
plasma torch. Element specific emission spectra are produced by a radio-frequency
inductively coupled plasma. The spectra are dispersed by a grating spectrometer,
and the intensities of the line spectra are monitored at specific wavelengths by a
photosensitive device. Photo currents from the photosensitive device are processed
and controlled by a computer system. A background correction technique is
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required to compensate for variable background contribution to the determination of
the analytes. Background should be measured adjacent to the analyte wavelength
during analysis. Possible interferences that can occur must be considered and
addressed appropriately as discussed in Section 4.
3.0 DEFINITIONS
3.1 CALIBRATION BLANK - A volume of reagent water acidified with the same acid
matrix reagents as in the calibration standards. The calibration blank is a zero
standard and is used to calibrate the AVICP instrument (Sects. 7.9.1).
3.2 CALIBRATION STANDARD (CAL) - A solution prepared from the dilution of
stock standard solutions. The CAL solutions contain the acid matrix reagents and
are used to calibrate the instrument response with respect to analyte concentration
(Sect. 7.8.1).
3.3 DISSOLVED ANALYTE - The concentration of analyte in an aqueous sample that
will pass through a 0.45-|im membrane filter assembly prior to sample acidification.
3.4 FIELD REAGENT BLANK (FRB) - An aliquot of reagent water that is placed in a
sample container in the laboratory and treated as a sample in all respects, including
shipment to the sampling site, exposure to the sampling site conditions, storage, acid
preservation, and all analytical procedures. The FRB is used to determine if method
analytes or interferences are present in the field environment (Sect. 8.2).
3.5 INSTRUMENT DETECTION LIMIT (IDL) - The concentration equivalent to the
analyte signal which is equal to three times the standard deviation of a series often
replicate measurements of the calibration blank signal at the same wavelength.
3.6 INSTRUMENT PERFORMANCE CHECK (IPC) SOLUTION - A solution of
method analytes in the acid matrix reagents used to evaluate the performance of the
instrument system with respect to a defined set of method criteria (Sects. 7.10.3 &
9.3.4).
3.7 LABORATORY DUPLICATES (LD1 and LD2) - Two aliquots of the same sample
taken in the laboratory and analyzed separately with identical procedures. Analyses
of LD1 and LD2 indicates precision associated with laboratory procedures, but not
with sample collection, preservation, or storage procedures.
3.8 LABORATORY FORTIFIED BLANK (LFB) - An aliquot of LRB to which known
quantities of the method analytes are added in the laboratory. The LFB is analyzed
exactly like a sample, and its purpose is to determine whether the methodology is in
control and whether the laboratory is capable of making accurate and precise
measurements (Sects. 7.9.3 & 9.3.2).
3.9 LABORATORY FORTIFIED SAMPLE MATRIX (LFM) - An aliquot of a
drinking water or drinking water supply sample to which known quantities of the
method analytes are added in the laboratory. The LFM is analyzed exactly like a
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sample, and its purpose is to determine whether the sample matrix contributes bias
to the analytical results. The background concentrations of the analytes in the
sample matrix must be determined in a separate aliquot and the measured values in
the LFM corrected for background concentrations (Sects. 1.6, 1.7 & 9.4).
3.10 LABORATORY REAGENT BLANK (LRB) - An aliquot of reagent water that is
treated exactly as a sample including exposure to all labware, equipment, and
reagents, that are used with other samples. The LRB is used to determine if method
analytes or other interferences are present in the laboratory environment, reagents,
or apparatus (Sects. 7.9.2 & 9.3.1).
3.11 LINEAR DYNAMIC RANGE (LDR) - The concentration range over which the
instrument response to an analyte is linear (Sect. 9.2.2).
3.12 MAXIMUM CONTAMINANT LEVEL (MCL) - The maximum permissible level
of a contaminant in water which is delivered to any user of a public water system.
3.13 METHOD DETECTION LIMIT (MDL) - The minimum concentration of an analyte
that can be identified, measured, and reported with 99% confidence that the analyte
concentration is greater than zero (Sects. 1.11, 1.12, 9.2.5 and Table 4).
3.14 PLASMA SOLUTION - A solution used to determine the nebulizer argon flow rate
or gas pressure that will produce the optimum net-signal-to-noise (S-B/B) needed
for the most requiring analyte included in the analytical scheme (Sects. 7.11 &
10.2).
3.15 QUALITY CONTROL SAMPLE (QC S) - A solution of method analytes of known
concentrations which is used to fortify an aliquot of LRB or sample matrix. The
QCS is obtained from a source external to the laboratory and different from the
source of calibration standards. It is used to check either laboratory or instrument
performance (Sects. 7.10.4 & 9.2.4).
3.16 SPECTRAL INTERFERENCE CHECK (SIC) SOLUTION - A solution of selected
method analytes of higher concentrations which is used to evaluate the procedural
routine for correcting known interelement spectral interferences with respect to a
defined set of method criteria (Sects. 4.1 & 9.3.5).
3.17 STANDARD ADDITION - The addition of a known amount of analyte to the
sample in order to determine the relative response of the detector to an analyte
within the sample matrix. The relative response is then used to assess either an
operative matrix effect or the sample analyte concentration (Sects. 1.6 & 11.3).
3.18 STOCK STANDARD SOLUTION - A concentrated solution containing one or
more method analytes prepared in the laboratory using assayed reference materials
or purchased from a reputable commercial source (Sect. 7.7).
3.19 TOTAL RECOVERABLE ANALYTE - For this method, the concentration of
analyte determined by the analysis of an unfiltered acid preserved drinking water
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sample following digestion by refluxing with hot dilute mineral acid(s) as specified
in the method (Sects. 1.5 & 11.1). Data are reported as a "total" element
determination - the combined concentrations of the dissolved and suspended
fractions of the sample.
4.0 INTERFERENCES
4.1 Spectral interferences are caused by background emission from continuous or
recombination phenomena, stray light from the line emission of high concentration
elements, overlap of a spectral line from another element, or unresolved overlap of
molecular band spectra. Except for interference from background emission and
possible stray light, which can usually be compensated for by subtracting the
background emission adjacent to the analyte wavelength peak, spectral interferences
associated with the analysis of drinking water are minimal. However, the absence of
interelement spectral interference should be verified. Criteria for determining an
interelement spectral interference is an apparent positive or negative
concentration on the analyte that is outside the 3-sigma control limits of the
calibration blank for the analyte. When an instrument equipped with a
conventional diffraction grating that provides 0.016 nm first order resolution is used
with the wavelengths in the noted spectral order and background correction
locations given in Table 1, no detectable concomitant interelement spectral
interferences occurs between the trace element analytes listed in this method at
concentrations < 20 mg/L. Since concentrations of trace elements in drinking water
and drinking water supplies are far below the level of 20 mg/L, an interelement
correction routine for trace analytes would be unnecessary for an instrument so
configured. On the other hand, the concentration of the water matrix elements can
be in excess of 100 mg/L. Fortunately, the matrix elements are not spectrally rich
and have few prominent lines to cause interelement spectral interference. Using this
method and analyzing single element solutions of 300 mg/L Ca, 200 mg/L Mg, 200
mg/L Na, and 100 mg/L Si, no spectral enhancement of other method analytes were
observed, thus not requiring interelement corrections. However, there are three
concerns worth noting: (1) yttrium, a commonly used internal standard, proved an
interference in the spectral region recommended for background correction on the
listed Ag wavelength (328.068 nm), (2) a similar situation occurs from molybdenum
on the spectral region recommended for background correction on the V wavelength
(292.402 nm), and (3) the listed Fe wavelength (271.441 nm) experiences an
apparent concentration increase of approximately 8% from cobalt (271.442 nm)
when the two analytes are present in equal concentration. Therefore, a quality
control check sample containing both iron and cobalt or both vanadium and
molybdenum should not be used to confirm the calibration standards when the Fe
271.441 nm and V 292.402 nm wavelengths are utilized.
Note: If wavelengths, noted spectral order, and background correction locations
different from those listed in Table 1 are used with this method, and/or the optical
resolution of the instrument utilized does not provide 0.016 nm first order resolution
or better, the absence of interelement spectral interference must be confirmed by
completing spectral scans over the wavelength area and background correction
locations to be utilized. The spectral scans should be completed using single
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element solutions of both trace and water matrix elements of concentrations noted
above that will verify nonexistent apparent analyte concentrations. If an
interelement spectral interference is detected, a correction routine that is operative
during analysis must be used with daily verification using SIC solutions, to
demonstrate that the routine meets the above criteria.
4.2 Physical interferences are effects associated with the sample nebulization and
transport processes. Changes in viscosity and surface tension can cause significant
inaccuracies, especially in samples containing high dissolved solids or high acid
concentrations. Physical interferences of the types described above have not been
evident in the analysis of most drinking waters. However, the use of a peristaltic
pump to regulate solution uptake rate and the use of mass flow controllers that
provide better control of the argon flow rates, especially for the nebulizer, improve
instrument stability and precision.
4.3 Chemical interferences include molecular-compound formation, ionization effects,
and solute-vaporization effects. In general, chemical interferences are highly
dependent on matrix type and the specific element. In radial ICP-AES, one way of
controlling these effects is careful selection of the observation height in the plasma.
However, for increased sensitivity, the total emission of the plasma is observed in
AVICP-AES, thus eliminating this useful option. To counteract ionization and
matrix interferences in AVICP-AES, some laboratories routinely use an ionization
buffer along with an internal standard added to both standards and samples alike in
the sample train using a peristaltic pump and mixing tee. Use of an ionization buffer
is permitted with this method provided the addition does not cause an interelement
spectral interference with a method analyte. However, in drinking water analyses
the use of an internal standard with pneumatic nebulization is discouraged because it
is not necessary and adds additional variance to the determination. The above stated
chemical interferences have not been observed using this method for drinking water
analyses when the operating conditions and preparations procedures are followed as
written.
4.4 Memory interferences result when analytes in a previous sample contribute to the
signals measured in a new sample. Memory effects can result from sample
deposition on the uptake tubing to the nebulizer and from the buildup of sample
material in the plasma torch and spray chamber. The site where these effects occur
is dependent on the element and can be minimized by flushing the system with a
rinse blank between samples (Sect. 7.9.4). The rinse times necessary for a particular
element should be estimated prior to analysis. For the water matrix elements this
may be achieved by aspirating a single element standard solution corresponding to
their LDRs (Sect. 3.11), while for the trace contaminants single element solutions
containing 10 mg/L are sufficient. The aspiration time should be the same as a
normal sample analysis period, followed by analysis of the rinse blank at designated
intervals. The length of time required to reduce analyte signal to within a factor of
10 times the calibration blank should be noted. Until the required rinse time is
established, this method requires a rinse period using the rinse blank of at least
30 sec between samples and standards. If a memory interference is suspected, the
sample should be re-analyzed after a long rinse period.
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5.0 SAFETY
5.1 The toxicity or carcinogenicity of each reagent used in this method have not been
fully established. Each chemical should be regarded as a potential health hazard and
exposure to these compounds should be as low as reasonably achievable. Each
laboratory is responsible for maintaining a current awareness file of OSHA
regulations regarding the safe handling of the chemicals specified in this method (3"5).
A reference file of material data handling sheets should also be made available to all
personnel involved in the chemical analysis. Specifically, concentrated nitric and
hydrochloric acids are moderately toxic and extremely irritating to skin and mucus
membranes. Use these reagents in a fume hood whenever possible and if eye or skin
contact occurs, flush with large volumes of water. Always wear safety glasses or a
shield for eye protection, protective clothing and observe proper mixing when
working with these reagents.
5.2 Acidification of samples should be done in a fume hood.
5.3 The inductively coupled plasma should only be viewed with proper eye protection
from the ultraviolet emissions.
5.4 It is the responsibility of the user of this method to comply with relevant disposal
and waste regulations. For guidance see Sections 14.0 and 15.0.
6.0 EQUIPMENT AND SUPPLIES
6.1 Axially viewed inductively coupled plasma emission spectrometer:
6.1.1 Computer-controlled emission spectrometer with background-correction
capability. The spectrometer must be capable of meeting and complying
with the requirements described and referenced in Section 2.2.
6.1.2 Radio-frequency generator compliant with FCC regulations.
6.1.3 Argon gas supply - High purity grade (99.99%). When analyses are
conducted frequently, liquid argon is more economical and requires less
frequent replacement of tanks than compressed argon in conventional
cylinders.
6.1.4 A variable speed peristaltic pump is required to deliver both standard and
sample solutions to the nebulizer.
6.1.5 (optional) A mass flow controller to regulate or monitor the argon flow
rate of the aerosol transport gas is highly recommended. Use of a mass
flow controller will provide more exacting control of reproducible plasma
conditions.
6.2 An analytical balance with capability to measure to 0.1 mg, for use in preparing
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standards and for weighing samples as may be required.
6.3 A temperature adjustable hot plate for preparing stock standard solutions.
6.4 A temperature adjustable block digester capable of maintaining a temperature of
95 °C for use with 50-mL plastic disposable digestion tube.
6.5 A gravity convection drying oven with thermostatic control capable of maintaining
180°C±5°C.
6.6 Air displacement pipetters capable of delivering volumes ranging from 50 |j,L to
10.0 mL with an assortment of high quality disposable pipet tips.
6.7 Labware - For determination of trace levels of elements, contamination and loss are
of prime consideration. Potential contamination sources include improperly cleaned
laboratory apparatus and general contamination within the laboratory environment
from dust, etc. A clean laboratory work area designated for trace element sample
handling should be used. Sample containers can introduce positive and negative
errors in the determination of trace elements by (1) contributing contaminants
through surface desorption or leaching, and (2) depleting element concentrations
through adsorption processes. All reusable labware (polyethylene,
polymethylpentene, PTFE, FEP, etc.) and plastic disposable digestion tubes, caps,
and watch glasses should be sufficiently clean for the task objectives. Several
cleaning procedures can provide clean labware. The procedure recommended for
reusable labware includes washing with a detergent solution, rinsing with tap water,
and soaking for 4 h or more in a mixture of 5% (v/v) FDSTO3 and 5% (v/v) HC1,
rinsing with reagent water and storing clean. (If digested LRBs indicate random
contamination, the plastic disposable digestion tubes, caps, and watch glasses should
be cleaned with 2% (v/v) FDSTO3 and rinsed with reagent water prior to use.)
Chromic acid cleaning solutions must be avoided because chromium is an analyte.
6.7.1 Plastic volumetric labware - PMP (polymethylpentene) or equivalent
metal free plastic volumetric flasks (50-mL to 500-mL capacities),
graduated cylinders (50-mL), and disposable metal-free plastic digestion
tubes with caps and watch glass covers.
6.7.2 (optional) PTFE Griffin beakers, 250-mL with PTFE covers for preparing
stock standards and reagents.
6.7.3 Narrow-mouth storage bottles, FEP (fluorinated ethylene propylene) and
LDPE (low density polyethylene) with screw closure, 60-mL to 500-mL
capacities.
6.7.4 One-piece stem FEP wash bottle with screw closure, 125-mL capacity.
7.0 REAGENTS AND STANDARDS
7.1 Reagents may contain elemental impurities which might affect analytical data. Only
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high-purity reagents that conform to the American Chemical Society specifications
must be used whenever possible. If the purity of a reagent is in question, analyze for
contamination. All acids used for this method should be of ultra high-purity grade
or equivalent. Trace metal grade acid may also be used if it can be verified by
analysis to be free of contamination. Suitable acids are available from a number of
manufacturers. Redistilled acids prepared by sub-boiling distillation are acceptable.
7.2 Hydrochloric acid, concentrated (sp.gr. 1.19) - HC1.
7.2.1 Hydrochloric acid (1+1) - Add 250 mL concentrated HC1 to 200 mL
reagent water and dilute to 500 mL.
7.2.2 Hydrochloric acid (1+20) - Add 10 mL concentrated HC1 to 200 mL
reagent water.
7.3 Nitric acid, concentrated (sp.gr. 1.41) - HNO3.
7.3.1 Nitric acid (1+1) - Add 250 mL concentrated HNO3 to 200 mL reagent
water and dilute to 500 mL.
7.3.2 Nitric acid (1+2) - Add 100 mL concentrated HNO3 to 200 mL reagent water.
7.3.3 Nitric acid (1+5) -Add 50 mL concentrated HNO3 to 250 mL reagent water.
7.3.4 Nitric acid (1+9) - Add 10 mL concentrated HNO3 to 90 mL reagent water.
7.4 Reagent water. All references to reagent water in this method refer to ASTM Type I
grade water(6).
7.5 Ammonium hydroxide, concentrated (sp. gr. 0.902).
7.6 Tartaric acid, ACS reagent grade.
7.7 Standard Stock Solutions - Stock standards may be purchased or prepared from
ultra-high purity grade chemicals (99.99 to 99.999% pure). All compounds must be
dried for 1 h at 105 °C, unless otherwise specified. It is recommended that stock
solutions be stored in acid-cleaned, never-used LDPE bottles for storage. Replace
stock standards when succeeding dilutions for preparation of calibration standards
can not be verified (see Sect. 9.2.4).
CAUTION: Many of these chemicals are extremely toxic if inhaled or
swallowed (Sect. 5.1). Wash hands thoroughly after handling.
Typical stock solution preparation procedures follow for 500-mL quantities, but for
the purpose of pollution prevention, the analyst is encouraged to prepare smaller
quantities when possible. Concentrations are calculated based upon the weight of
the pure element or upon the weight of the compound multiplied by the fraction of
the analyte in the compound.
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7.7.1 Aluminum solution, stock, 1 mL = 1000 |ig Al: Dissolve 0.500 g of
aluminum metal, weighed accurately to at least three significant figures, in
an acid mixture of 4.0 mL of (1+1) HC1 and 1.0 mL of concentrated HN03
in a beaker. Warm beaker slowly to effect solution. When dissolution is
complete, transfer solution quantitatively to a 500-mL PMP flask, add an
additional 5.0 mL of (1+1) HC1 and dilute to volume with reagent water.
7.7.2 Antimony solution, stock, 1 mL = 1000 |ig Sb: Dissolve 0.500 g of
antimony powder, weighed accurately to at least three significant figures,
in 10.0 mL (1+1) HNO3 and 5.0 mL concentrated HC1 in a beaker. Add
50 mL reagent water and 0.75 g tartaric acid. Warm solution slightly to
effect complete dissolution. Cool solution and add reagent water to
volume in a 500-mL PMP volumetric flask.
7.7.3 Arsenic solution, stock, 1 mL = 1000 |ig As: Dissolve 0.660 g of As2O3
(As fraction = 0.7574), weighed accurately to at least three significant
figures, in 50 mL of reagent water containing 5.0 mL concentrated
NH4OH in a beaker. Warm the solution gently to effect dissolution.
Acidify the solution with 10.0 mL concentrated HNO3 and dilute to
volume in a 500-mL PMP volumetric flask with reagent water.
7.7.4 Barium solution, stock, 1 mL = 1000 |ig Ba: Dissolve 0.719 g BaCO3
(Ba fraction = 0.6960), weighed accurately to at least three significant
figures, in a beaker containing 75 mL (1+2) HNO3 with heating and
stirring to degas and dissolve compound. Let solution cool and dilute with
reagent water in 500-mL PMP volumetric flask.
7.7.5 Beryllium solution, stock, 1 mL = 1000 jig Be: DO NOT DRY. Dissolve
9.823 g BeSCy4H2O (Be fraction = 0.0509), weighed accurately to at
least four significant figures, in reagent water, add 5.0 mL concentrated
HNO3, and dilute to volume in a 500-mL PMP volumetric flask with
reagent water.
7.7.6 Boron solution, stock, 1 mL = 1000 jig B: DO NOT DRY. Dissolve
2.859 g anhydrous H3BO3 (B fraction = 0.1749), weighed accurately to at
least four significant figures, in reagent water and dilute in a 500-mL PMP
volumetric flask with reagent water.
7.7.7 Cadmium solution, stock, 1 mL = 1000 |ig Cd: Dissolve 0.500 g Cd
metal, acid cleaned with (1+9) HNO3, weighed accurately to at least three
significant figures, in 25 mL (1+1) HNO3 in a beaker with heating to
effect dissolution. Let solution cool and dilute with reagent water in a
500-mL PMP volumetric flask.
7.7.8 Calcium solution, stock, 1 mL = 1000 |ig Ca: Suspend 1.249 g CaCO3
(Ca fraction = 0.4005), dried at 180 °C for 1 h before weighing, weighed
accurately to at least four significant figures, in reagent water and dissolve
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cautiously with a minimum amount of (1+1) HNO3. Add 5.0 mL
concentrated HNO3 and dilute in a 500-mL PMP volumetric flask with
reagent water.
7.7.9 Chromium solution, stock, 1 mL = 1000 |ig Cr: Dissolve 0.962 g CrO3
(Cr fraction = 0.5200), weighed accurately to at least three significant
figures, in 60 mL (1+5) HNO3. When dissolution is complete, dilute in a
500-mL PMP volumetric flask with reagent water.
7.7.10 Copper solution, stock, 1 mL = 1000 |ig Cu: Dissolve 0.500 g Cu metal,
acid cleaned with (1+9) HNO3, weighed accurately to at least three
significant figures, in 25 mL (1+1) HNO3 in a beaker with heating to
effect dissolution. Let solution cool and dilute in a 500-mL PMP
volumetric flask with reagent water.
7.7.11 Iron solution, stock, 1 mL = 1000 |ig Fe: Dissolve 0.500 g Fe metal, acid
cleaned with (1+1) HC1, weighed accurately to three significant figures, in
50 mL (1+1) HC1 in a beaker with heating to effect dissolution. Let
solution cool and dilute in a 500-mL PMP volumetric flask with reagent
water.
7.7.12 Lead solution, stock, 1 mL = 1000 jig Pb: Dissolve 0.799 g Pb(NO3)2
(Pb fraction = 0.6256), weighed accurately to at least three significant
figures, in a minimum amount of (1+1) FINO3. Add 10.0 mL (1+1) FDSTO3
and dilute in a 500-mL PMP volumetric flask with reagent water.
1.1 .\1> Magnesium solution, stock, 1 mL = 1000 |ig Mg: Dissolve 0.500 g of
cleanly polished Mg ribbon, accurately weighed to at least three
significant figures, in slowly added 2.5 mL (1+1) HC1 (CAUTION:
reaction is vigorous). Add 10.0 mL (1+1) F£NO3 and dilute in a 500-mL
PMP volumetric flask with reagent water.
7.7.14 Manganese solution, stock, 1 mL = 1000 |ig Mn: Dissolve 0.500 g of
manganese metal, weighed accurately to at least three significant figures,
in 25 mL (1+1) HNO3 and dilute to volume in a 500-mL PMP volumetric
flask with reagent water.
7.7.15 Nickel solution, stock, 1 mL = 1000 |ig Ni: Dissolve 0.500 g of nickel
metal, weighed accurately to at least three significant figures, in 10.0 mL
hot concentrated FDSTO3, cool, and dilute in a 500-mL PMP volumetric
flask with reagent water.
7.7.16 Selenium solution, stock, 1 mL = 1000 |ig Se: Dissolve 0.703 g SeO2
(Se fraction = 0.7116), weighed accurately to at least three significant
figures, in 100 mL reagent water and dilute to volume in a 500-mL PMP
volumetric flask with reagent water.
7.7.17 Silica solution, stock, 1 mL = 1000 jig SiO2: DO NOT DRY. Dissolve
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1.482 g (NH4)2SiF6, weighed accurately to at least four significant figures,
in 100 mL (1+20) HC1 in a beaker with heating at 85 °C to effect
dissolution. Let solution cool and dilute in a 500-mL PMP volumetric
flask with reagent water.
7.7.18 Silver solution, stock, 1 mL = 1000 |ig Ag: Dissolve 0.500 g Ag metal,
weighed accurately to at least three significant figures, in 50 mL (1+1)
HNO3 in a beaker with heating to effect dissolution. Let solution cool and
dilute in a 500-mL PMP volumetric flask with reagent water.
7.7.19 Sodium solution, stock, 1 mL = 1000 |ig Na: Dissolve 1.271 g NaCl
(Na fraction = 0.3934), weighed accurately to at least four significant
figures, in reagent water. Add 5.0 mL concentrated HNO3 and dilute to
volume in a 500-mL PMP volumetric flask with reagent water.
7.7.20 Tin solution, stock, 1 mL = 1000 |ig Sn: Dissolve 0.500 g Sn shot,
weighed accurately to at least three significant figures, in an acid mixture
of 5.0 mL concentrated HC1 and 1.0 mL (1+1) HNO3 in a beaker with
heating to effect dissolution. Let solution cool, add 100 mL concentrated
HC1, and dilute to volume in a 500-mL PMP volumetric flask with reagent
water.
7.7.21 Vanadium solution, stock, 1 mL = 1000 |ig V: Dissolve 0.500 g V metal,
acid cleaned with (1+9) HNO3, weighed accurately to at least three
significant figures, in 25 mL (1+1) HNO3 in a beaker with heating to
effect dissolution. Let solution cool and dilute in a 500-mL PMP
volumetric flask with reagent water.
7.7.22 Zinc solution, stock, 1 mL = 1000 |ig Zn: Dissolve 0.500 g Zn metal, acid
cleaned with (1+9) HNO3, weighed accurately to at least three significant
figures, in 25 mL (1+1) HNO3 in a beaker with heating to effect
dissolution. Let solution cool and dilute in a 500-mL PMP volumetric
flask with reagent water.
7.8 Calibration Standard Solutions.
7.8.1 Mixed Calibration Standard Solutions - For total recoverable analyses
prepare mixed calibration standard solutions by combining appropriate
volumes of the stock solutions in 500-mL PMP volumetric flasks
containing 20 mL (1+1) HNO3 and 10 mL (1+1) HC1 and dilute to volume
with reagent water. Prior to preparing the mixed standards, each stock
solution should be analyzed separately to determine possible spectral
interferences or the presence of impurities. Care should be taken when
preparing the mixed standards to ensure that the elements are compatible
and stable together. To minimize the opportunity for contamination by the
containers, it is recommended to transfer the mixed-standard solutions to
acid-cleaned, never-used FEP fluorocarbon (FEP) bottles for storage.
Fresh mixed standards should be prepared, as needed, with the realization
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that concentrations can change on aging. Calibration standards not
prepared from primary standards must be initially verified using a certified
reference solution. Recommended wavelengths and calibration
concentrations are listed in Table 1. Typical calibration standard
combinations are given in Table 2.
7.8.2 Sodium Multi-point Calibration Standards - To determine elevated
concentrations of Na in drinking water and drinking water supplies using
the recommended wavelength, Na is determined using a multi-point
analytical calibration usable to 160 mg/L. Prepare in a mixture of 2%
HNO3 (v/v) and 1% HC1 (v/v) a calibration blank and six calibration
standards at concentrations of 5, 10, 20, 40, 80, and 160 mg/L,
respectively. To create the multi-point calibration, curve-fit the response
of the blank and standards and store as a computer file. This calibration is
standardized before each period of analysis using the calibration blank and
the mixed calibration standard solution containing 20 mg/L Na
(Sect. 7.8.1). A new multi-point calibration should be prepared whenever
there is a change in analytical performance caused by either a change in
instrument hardware or operating conditions. (Of the 990 ground water
samples analyzed in the National Inorganic Radionuclide Survey, Na was
reported below 90 mg/L in 84% of the samples.)
7.9 Blanks - Four types of blanks are required for this method. The calibration blank is
used in establishing the analytical curve, the laboratory reagent blank is used to
assess possible contamination from the laboratory procedure, the laboratory fortified
blank is used to assess routine laboratory performance and a rinse blank is used to
flush the uptake system to reduce memory interferences.
7.9.1 The calibration blank is prepared by diluting 20 mL (1+1) HNO3 and 10
mL (1+1) HC1 in a 500-mL PMP volumetric flask to volume with reagent
water. Store the prepared blank solution to an acid-cleaned, never-used
500-mL FEP bottle. This bottle should be dedicated for reuse and storage
of this solution.
7.9.2 The laboratory reagent blank (LRB) is prepared by carrying 50 mL of
reagent water through the entire analytical procedure. The LRB must
contain all the reagents in the same volumes as used in processing the
samples.
7.9.3 The laboratory fortified blank (LFB) is prepared in the same manner as the
LRB, and fortified by adding 1.0 mL of the fortifying solution (7.10.1) to
50 mL of LRB. The LFB must be carried through the entire analytical
procedure. The analyte concentrations fortified in the LFB are as follows:
4 |ig/L Be; 5 |ig/L Cd; 6 |ig/L Sb; 10 |ig/L As; 15 |ig/L Pb; 50 |ig/L Ag,
Mn, Se, Sn and V; 100 |ig/L B, Cr and Ni; 200 |ig/L Al; 300 |ig/L Fe;
1000|ig/LBa, CuandZn.
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7.9.4 The rinse blank is prepared by acidifying reagent water in an acid-cleaned
LDPE bottle to concentrations of 2% (v/v) HNO3 + 2% (v/v) HC1.
7.10 Quality Control Solutions.
7.10.1 Fortifying solution - The fortifying solution is used to prepare the
laboratory fortified blank (LFB) and laboratory fortified matrix (LFM)
solutions. The fortifying solution should be prepared in a 100-mL PMP
volumetric flask, containing a mixture of 4 mL (1+1) HNO3 and 2 mL
(1+1) HC1, by combining the following listed aliquot volumes of each
stock standard and the low-level stock fortifying solution (7.10.2) and
diluting to volume with reagent water: 5 mL Ba, Cu & Zn and the low-
level stock fortifying solution; 1.5 mL Fe; 1.0 mL Al; 0.5 mL B, Cr & Ni;
and 0.25 mL Ag, Mn, Se, Sn & V. Store in a new, acid-cleaned LDPE
bottle. The analyte concentrations in the fortifying solution are as follows:
50 mg/L Ba, Cu & Zn; 15 mg/L Fe; 10 mg/L Al; 5.0 mg/L B, Cr & Ni;
2.5 mg/L Ag, Mn, Se, Sn & V; 0.75 mg/L Pb; 0.50 mg/L As; 0.30
mg/L Sb; 0.25 mg/L Cd; and 0.20 mg/L Be.
7.10.2 Low-level stock fortifying solution - The low-level stock fortifying
solution is used to prepare the fortifying solution described in Section
7.10.1. The low-level stock fortifying solution is prepared in a 50-mL
PMP volumetric flask, containing a mixture of 2 mL (1+1) HNO3 and
1 mL (1+1) HC1, by combining the following listed aliquot volumes of
each stock standard and diluting to volume with reagent water: 750 jiL Pb
(15 mg/L); 500 |iL As (10 mg/L); 300 |iL Sb (6 mg/L); 250 |iL Cd
(5 mg/L); and 200 jiL Be (4 mg/L). (The concentration in parenthesis is
that of the analyte in the low-level stock.) Store in a new, acid-cleaned
LDPE bottle dedicated for reuse and repeated storage of this solution.
7.10.3 Instrument Performance Check (IPC) Solution - The IPC solution is used
to periodically verify instrument performance during analysis. It should
be prepared by combining method analytes at appropriate concentrations
in the same acid mixture (2% HNO3 + 1% HC1) as the calibration
standards. Silver should be limited to < 100 |ig/L; while Al and Fe should
be made to a concentration of 2 mg/L; Ca, Mg, and SiO2 made to 5 mg/L;
and Na to a concentration of 10 mg/L. For all other analytes, a
concentration of 200 |ig/L is recommended. The IPC should be prepared
in a PMP (metal-free plastic) volumetric flask to avoid B and SiO2
contamination. Store the IPC solution in a new, acid-cleaned FEP bottle
dedicated for reuse and repeated storage of this solution.
NOTE: If the instrument readout system incorporates the use of a dilution
factor (0.5) to report original sample concentration prior to processing,
and the IPC solution is analyzed in the same manner as the samples, the
reported IPC concentrations will be half the concentrations listed above.
7.10.4 Quality Control Sample (QCS) - Analysis of a QCS is required for initial
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and periodic verification of calibration standards or stock standard
solutions in order to verify instrument performance. The QCS must be
obtained from outside source different from the standard stock solutions
and prepared in a PMP volumetric flask using the same acid mixture as the
calibration standards. The concentration of the analytes in the QCS
solution should be sufficient to meet the data quality objectives given in
Section 9.2.4. The concentrations may range from 200 |ig/L for sensitive
analytes such as Be and Cd to > 2.0 mg/L for Al, Ca, Fe, Mg, Na, and
SiO2. However, the concentration of Ag should be limited to 0.1 mg/L or
less to ensure complete solubility and stability. The QCS solution should
be stored in a new, acid-cleaned LDPE bottle and analyzed as needed to
meet data-quality needs. A fresh solution should be prepared quarterly or
more frequently as needed.
7.11 Plasma Solution - The plasma solution is used for determining the nebulizer argon
flow rate or gas pressure that will produce the optimum net-signal-to-background
noise (S-B/B) ratio needed for the most requiring analytes included in the method
without degrading the performance of the other analytes. The two analytes that
present the greatest challenge are Sb and As because of the low MCLs and limited
analytical sensitivity. The combined 1 mg/L solution is prepared by adding 100 jiL
of the Sb stock standard (7.7.2) and a 100 jiL of the As stock standard (7.7.3) to a
mixture of 4 mL (1+1) HNO3 and 2 mL (1+1) HCL in a 100-mL PMP volumetric
and diluting to volume with reagent water. Store the solution in a new, acid-cleaned
LPDE bottle for repeated use as necessary.
8.0 SAMPLE COLLECTION. PRESERVATION. AND STORAGE
8.1 For the determination of trace and water matrix elements in drinking water and
drinking water supplies, samples are not filtered, but acidified with (1+1) nitric acid
to a pH < 2 (3 mL of [1+1] acid per liter of sample should be sufficient).
Preservation may be done at the time of collection; however, to avoid the hazards of
strong acids in the field, transport restrictions and possible contamination, it is
recommended that the samples be returned to the laboratory within two weeks of
collection and acid preserved upon receipt in the laboratory. Following
acidification, the sample should be mixed, held for sixteen hours, and then verified
to be pH < 2 just prior to withdrawing an aliquot for sample processing. If for some
reason, such as high alkalinity, the sample pH is verified to be > 2, more acid must
be added and the sample held for sixteen hours until verified to be pH < 2. If
properly preserved, the sample can be held up to 6 months.
8.2 If required by the data user, a field reagent blank (Sect. 3.4) should be prepared and
analyzed in the same manner as a collected sample. Use the same type of container
and acid as used in sample collection.
9.0 QUALITY CONTROL
9.1 Each laboratory using this method is required to operate a formal quality control
(QC) program. The minimum requirements of this program consists of an initial
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demonstration of laboratory capability, and the periodic analysis of laboratory
reagent blanks, fortified blanks and other laboratory solutions as a continuing check
on performance. The laboratory is required to maintain performance records that
define the quality of the data thus generated.
9.2 Initial Demonstration of Performance (mandatory).
9.2.1 The initial demonstration of performance is used to characterize instrument
performance (determination of linear dynamic ranges and analysis of
quality control samples) and laboratory performance (determination of
method detection limits) prior to analyses conducted by this method.
9.2.2 Linear dynamic range (LDR) - The upper limit of the LDR must be
established for each wavelength used for the analysis of the drinking water
matrix analytes: Ca, Mg and silica. It must be determined from a linear
calibration prepared using the established instrument operating conditions.
The LDR should be determined by analyzing succeedingly higher standard
concentrations of the analyte until the observed analyte concentration is no
more than 10% below the stated concentration of the standard. Determined
LDRs must be documented and kept on file. The LDR which may be used
for the analysis of samples should be judged by the analyst from the
resulting data. Determined sample analyte concentrations that are greater
than 90% of the determined upper LDR limit must be diluted and
reanalyzed. The LDRs should be verified as required for certification or
whenever, in the judgment of the analyst, a change in analytical
performance caused by either a change in instrument hardware or operating
conditions would dictate they be redetermined.
9.2.3 Non-linear dynamic range - The upper limit of the non-linear calibration
used for the determination of Na is the highest standard used to describe the
calibration curve. The non-linear calibration must be established using the
same instrument operating conditions used for analysis. Determined
sample concentrations that are > 10% above the upper limit for Na must be
diluted and reanalyzed. The upper limit should be verified as required for
certification or whenever, in the judgment of the analyst, a change in
analytical performance caused by either a change in instrument hardware or
operating conditions would dictate they be redetermined.
9.2.4 Quality control sample (QCS) - When beginning the use of this method, on
a quarterly basis, after the preparation of stock or calibration standard
solutions, or as required to meet data-quality needs, verify the calibration
standards and acceptable instrument performance with the preparation and
analysis of a QCS (Sect. 7.10.4.) To verify the calibration standards, the
determined mean concentrations from 3 analyses of the QCS must be
within ± 5% of the stated values. If the calibration standard can not be
verified, performance of the determinative step of the method is
unacceptable. The source of the problem must be identified and corrected
before either proceeding on with the initial determination of method
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detection limits or continuing with on-going analyses.
9.2.5 Method detection limit (MDL) - MDLs must be established for all
wavelengths utilized for trace element determinations in total recoverable
digestates. MDLs are determined using reagent water (blank) fortified to a
concentration ranging from the instrument detection limit (IDL) to
approximately two times the IDL(7) (see Table 4 for typical levels). To
determine MDL values, take seven replicate aliquots of the fortified reagent
water and process through the entire total recoverable analytical procedure.
Perform all calculations defined in the method and report the concentration
values in the appropriate units. Calculate the MDL as follows:
MDL = (t) x (S)
where: t = students' t value for a 99% confidence level and
a standard deviation estimate with n-1 degrees
of freedom (t = 3.14 for seven replicates).
S = standard deviation of the replicate analyses.
Note: If the relative standard deviation (RSD) from the analyses of the
seven aliquots is < 10% and neither random nor reagent contamination is
operative, the concentration used to determine the analyte MDL may have
been inappropriately high for the determination. If so, this could result in
the calculation of an unrealistically low MDL. In this case the MDL
determination should be repeated using a lower concentration. Although
data can be reported down to the MDL, the associated variability (RSD
> 30%) at the MDL concentration is very high. A more realistic reporting
limit is the estimated upper limit of the 95% confidence interval about the
MDL. This limit is based on the 97.5 percentile of chi square over
associated 6 degrees of freedom and is computed by multiplying the MDL
by a factor of 2.2(8). Typical single laboratory MDLs and reporting limits
values using this method are given in Table 4.
The MDLs must be sufficient to meet data quality needs and detect analytes
at the required levels according to compliance monitoring regulation
(Sect. 1.2). Specifically, the determined MDLs for the analytes: As, Be,
Cd, Sb, Se and Pb must be < 1/5 their respective MCL or action level
before this method can be used for compliance monitoring. MDLs should
be determined as required for laboratory certification, when a new operator
begins work or whenever, in the judgment of the analyst, a change in
analytical performance caused by either a change in instrument hardware or
operating conditions would dictate they be redetermined.
9.3 Assessing Laboratory Performance (mandatory)
9.3.1 Laboratory reagent blank (LRB) - The laboratory must analyze at least one
LRB (Sect. 7.9.2) with each batch of 20 or fewer samples. LRB data are
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used to assess contamination from the laboratory environment. LRB values
that exceed the MDL indicate laboratory or reagent contamination should
be suspected. When LRB values for the trace analytes are above the
calculated reporting limit (2.2 times the analyte MDL), fresh aliquots of the
samples must be prepared and analyzed again for the affected analytes after
the source of contamination has been corrected and acceptable LRB values
have been obtained.
9.3.2 Laboratory fortified blank (LFB) - The laboratory must analyze at least one
LFB (Sect. 7.9.3) with each batch of samples. Calculate accuracy as
percent recovery using the following equation:
LFB
R= X 100
where: R = percent recovery.
LFB = laboratory fortified blank determined concentration.
s = concentration equivalent of analyte added to fortify
the LRB solution.
If the recovery of any analyte falls outside the required control limits of
90-110%, that analyte is judged to be out of control, and the source of the
problem should be identified and resolved before continuing analyses.
9.3.3 The laboratory must use LFB analyses data to assess laboratory
performance against the appropriate required control limits of 90-110%
(see Sect.9.3.2). When sufficient internal performance data become
available (usually a minimum of twenty to thirty analyses), optional control
limits can be developed from the mean percent recovery (x) and the
standard deviation (S) of the mean percent recovery. These data can be
used to establish the upper and lower control limits as follows:
UPPER CONTROL LIMIT = x + 3S
LOWER CONTROL LIMIT = x - 3S
The optional control limits must be equal to or better than the appropriate
required control limits. After each five to ten new recovery measurements,
new control limits can be calculated using only the most recent twenty to
thirty data points. Also, the standard deviation (S) data should be used to
establish an on-going precision statement for the level of concentrations
included in the LFB. These data must be kept on file and be available for
review.
9.3.4 Instrument performance check (IPC) solution - The laboratory must initially
and periodically verify that the instrument calibration is within required
control limits. For all determinations the laboratory must analyze the IPC
solution (Sect. 7.10.3) and a portion of the calibration blank immediately
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following calibration, after every tenth sample and at the end of the sample
run. Analysis of the calibration blank should always be less than the
calculated reporting limit (2.2 times the analyte MDL) for the trace
elements. Analysis of the IPC solution immediately following calibration
must verify that the instrument is within ± 5% of calibration. Subsequent
analyses of the IPC solution must be within ± 10% of calibration. If the
calibration can not be verified within the specified limits, reanalyze both
the IPC solution and the calibration blank. If the second analysis confirms
calibration to be outside the limits, sample analysis must be discontinued,
the cause determined, corrected and/or the instrument recalibrated. All
samples following the last acceptable IPC solution analysis must be
reanalyzed. The analyses data of the IPC solution should be kept on file
with the sample analyses data.
9.3.5 Spectral interference check (SIC) solution - For this method using the listed
wavelengths, the specified background locations, and an instrument with
first order resolution of 0.016 nm or better, verification of interelement
spectral interference is not required. However, if method flexibility,
allowing the use of different wavelengths, spectral orders, and background
correction locations requires an interelement correction routine for spectral
interference, it must be verified daily with the use of SIC solutions
(see Sect. 4.1 for listed criteria and description of required testing).
9.4 Assessing Total Recoverable Analyte Recovery and Data Quality
9.4.1 Sample non-homogeneity and the chemical nature of the sample matrix can
affect analyte recovery and the quality of the data. In the analysis of
finished drinking water, these aspects are rarely an issue. However, source
water for a drinking water supply can have varying turbidity. Taking
separate aliquots from the sample for replicate and fortified analyses can, in
some cases, assess the effect. Unless otherwise specified by the data user,
laboratory or program, the following laboratory fortified matrix (LFM)
procedure (Sect. 9.4.2) is required.
9.4.2 The laboratory must add a known amount of each analyte to a minimum of
10% of the routine samples. The LFM aliquot must be a duplicate of the
aliquot used for sample analysis and fortified prior to sample preparation.
The added analyte concentration must be the same as that used in the
laboratory fortified blank (Sect. 7.9.3). Over time, samples from all routine
sample sources should be fortified.
9.4.3 Calculate the percent recovery for each analyte, corrected for analyte
background concentrations greater than the calculated reporting limit
measured in the unfortified sample, and compare these values to the
designated LFM recovery range of 85-115%. Percent recovery may be
calculated using the following equation:
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c.-c
R= x 100
where: R = percent recovery.
Cs = fortified sample concentration.
C = sample background concentration (>2.2 X MDL).
s = concentration equivalent of analyte
added to fortify the sample.
9.4.4 If the recovery of any analyte falls outside the designated LFM recovery
range, and the laboratory performance for that analyte is shown to be in
control (Sect. 9.3), the recovery problem encountered with the fortified
sample is judged to be matrix related, not system related. If the analyte in
question is a primary contaminant (Sect. 1.1), under certain circumstances
additional analyses may be required (see Sects. 1.6 and 1.7). For a primary
contaminant not requiring additional analysis, for a secondary contaminant,
or non-regulated analyte, the data user should be informed that the result
for that analyte is suspect due to matrix effects.
9.4.5 Where reference materials are available, they should be analyzed to provide
additional performance data. The analysis of reference samples is a
valuable tool for demonstrating the ability to perform the method
acceptably.
10.0 CALIBRATION AND STANDARDIZATION
10.1 Specific wavelengths and calibration concentrations are listed in Table 1. Other
wavelengths may be substituted if they can provide the needed sensitivity and are
corrected for spectral interference (see Sect. 4.1). However, because of the
difference among various makes and models of spectrometers, specific instrument
operating conditions are not required. The instrument and operating conditions
utilized for determination must be capable of providing data of acceptable quality
(see Sect. 1.12) to the drinking water program and data user. The analyst should
follow the instructions provided by the instrument manufacturer; however,
instrument operating conditions used to collect the single laboratory performance
data included in this method are listed in Table 3 and are provided as a
recommendation. Once operating conditions are established, it is intended that daily
calibration will be accomplished using a calibration blank and a single analyte
concentration.
10.2 Prior to using this method, optimize the plasma operating conditions. The purpose
of plasma optimization is to provide a maximum net signal-to-background ratio
(S-B/B) for the determination of As and Sb, the most requiring elements in the
analytical array. The use of a mass flow controller to regulate or monitor the
nebulizer gas flow rate greatly facilitates the procedure. The following procedure is
recommended:
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10.2.1 Ignite the plasma, and using the conditions listed in Table 3 as a guide,
select appropriate incident if power and plasma gas flows. Allow the
instrument to become thermally stable before beginning. This usually
requires approximately 30 minutes of operation. Set the aerosol argon flow
rate through the nebulizer at approximately 650 mL per minute or at the
instrument manufacturer's recommended pressure setting if the flow rate
can not be measured. Following the instrument manufacture's instructions,
optically profile the instrument to provide maximum signal for all
wavelengths. While aspirating reagent water and using the As channel
signal, adjust the horizontal and vertical position of the torch to provide
minimum signal intensity. This should align the optics with the center of
the sample channel of the plasma and minimize background noise.
10.2.2 After profiling the torch, aspirate the plasma solution (Sect. 7.11) and while
following the instrument manufacturer's instructions, adjust the aerosol
carrier gas flow rate through the nebulizer and collect signal intensity
readings (S) at equal incremental flow settings on either side of the initial
flow rate setting. Suggested flow rates (mL/min) settings are: 590, 600,
610, 620, 630, 640, 650, 660, 670, 680, 690 and 700. (NOTE: If nebulizer
flow rates can not be measured, incremental pressure settings that control
flow should be used.) After acid rinsing to eliminate any possible memory
effect, repeat the same operation using an acid blank solution and collect
the blank signal intensity readings (B) at the same respective flow settings.
Calculate the S-B/B ratio for As and Sb at each flow setting. Plot, on the
same graph, the calculated ratios and the blank intensity readings versus the
argon flow rates. The intensity counts for the blank signal should decrease
at a uniform rate as the argon flow rate increases, while the calculated
S-B/B ratios for Sb should increase. At the lower flow rate settings, the As
ratios should remain nearly constant; however, at some point the As ratio
will start to decrease with an increase in flow rate. The flow rate where the
As ratio begins to decrease (2% or more) is the limiting flow and the flow
rate just prior to the limiting flow should be selected for routine operation.
Record the nebulizer gas flow rate or pressure setting for future reference.
If the nebulizer is replaced with a new or different nebulizer, repeat this
optimization procedure.
10.2.3 After establishing the nebulizer gas flow rate, determine the solution uptake
rate of the nebulizer in mL/min by aspirating a known volume calibration
blank for a period of at least 3 minutes. Divide the spent volume by the
aspiration time (in minutes) and record the uptake rate. Set the peristaltic
pump to deliver the uptake rate in a steady even flow.
10.2.4 The final instrument operating condition, selected as being optimum,
should provide acceptable instrument detection limits and method detection
limits for all trace analytes. Refer to Table 4 for comparison of IDLs and
MDLs, respectively.
10.2.5 Before daily calibration and after the instrument warmup period, the
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nebulizer gas flow should be reset to the determined optimized flow. If a
mass flow controller is being used, it should be reset to the recorded
optimized flow rate. In order to maintain reliable MDLs, the nebulizer gas
flow rate should be the same from day-to-day (<2% change).
10.3 Before using the procedure (Sect. 11.0) to analyze samples, there must be data
available documenting initial demonstration of performance. The required data and
procedures are described in Sections 9.2.2, 9.2.3, 9.2.4, and 9.2.5. These data must
be generated using the same instrument operating conditions and respective
calibration routines used for sample analysis (see Sect. 11.2). These documented
data must be kept on file and be available for review by the data user.
10.4 After completing the initial demonstration of performance, but before analyzing
samples, the laboratory, if needed, must establish and initially verify the
interelement spectral interference correction routine to be used during sample
analysis. A general description concerning spectral interference and the analytical
requirements for background correction are given in Sections 4.1 and 9.3.5. Once
established, the entire routine must be verified on a daily basis by analyzing SIC
solution(s) resulting in response data that falls within the 3-sigma control limits of
the calibration blank of the analyte (Sect. 4.1).
11.0 PROCEDURE
11.1 Sample Preparation (Total Recoverable Digestion) - For the determination of trace
analytes and water matrix elements in drinking water and source water supply, using
a 50-mL PMP graduated cylinder, transfer a 50 mL (± 0.5 mL) aliquot from a well-
mixed, acid preserved sample to a 50-mL clean digestion tube containing a mixture
of 1.0 mL (1+1) HNOj (Sect. 7.3.1) and 0.5 mL (1+1) HC1 (Sect. 7.2.1). (The acids
should be added to the digestion tube using an air displacement pipetter - see Sect.
6.6.) Place the digestion tube in the block digester (Sect. 6.4). (The block digester
should be located in a clean fume hood.) Power the digestion block to preselected
settings to evaporate the sample at a temperature of 95 °C (± 2 °C). Preconcentrate
the sample until the volume has been reduced to approximately 25 mL. Cover the
digestion tube with a plastic watch glass and reflux the sample for 30 minutes. (The
time required to complete this step should approximate 2.5 h.) Once the refluxing
step is complete, remove the digestion tube from the block digester and allow the
sample to cool. When cool, using the volume gradation marks on the digestion tube,
adjust the sample volume to 25 mL with reagent water (Sect. 7.4). Cap the digestion
tube and mix. The sample is now ready for analysis. Because the effects of various
matrices on the stability of analytes in low concentration can not be characterized,
all analyses should be performed as soon as possible after the completed
preparation.
11.2 Sample Analysis
11.2.1 Prior to daily calibration of the instrument, inspect the sample introduction
system, including the nebulizer, torch, injector tube and uptake tubing, for
salt deposits, dirt and debris that would restrict solution flow and affect
200.5-24
-------
instrument performance. Clean the system when needed or on a daily basis.
11.2.2 Configure the instrument system to the selected power and operating
conditions as determined in Sections 10.1 and 10.2.
11.2.3 The instrument should be allowed to become thermally stable before
calibration and analyses. This usually requires at least 30 minutes of
operation. After instrument warmup, complete any required optical
profiling or alignment routines particular to the instrument.
11.2.4 For initial and daily operation, calibrate the instrument according to the
instrument manufacturer's recommended procedures, using mixed
calibration standard solutions (Sect. 7.8.1) and the calibration blank
(Sect. 7.9.1). A peristaltic pump must be used to introduce all solutions to
the nebulizer. To allow equilibrium to be reached in the plasma, aspirate
all solutions for 20 sec after reaching the plasma before beginning
integration of the background corrected signal to accumulate data. To
reduce measurement variance, use the average value of replicate integration
periods of the signal to be correlated to analyte concentration. (Suggested
data collection period for all determinations: 5 replicate 24 sec periods [8
sec on the wavelength peak and 8 sec on each BKGD location] = 120 sec.)
Flush the system with the rinse blank (Sect. 7.9.4) for a minimum of 30
seconds (Sect. 4.4) between each standard.
11.2.5 After completion of the initial requirements of this method (Sects. 10.3 and
10.4), samples should be analyzed in the same operational manner used in
the calibration routine with the rinse blank also being used between all
sample solutions and quality control check solutions.
11.2.6 During sample analysis the laboratory must comply with the required
quality control described in Sections 9.3 and 9.4.
11.2.7 Determined water matrix element concentrations that are 90% or more of
the upper limit of the analyte LDR, or in the case of Na above the multi-
point calibration range, must be diluted with reagent water that has been
acidified in the same manner as the calibration blank and reanalyzed.
11.2.8 To ensure an accurate determination for compliance monitoring, a primary
contaminant must be reanalyzed by either method of standard additions
(see Sect. 11.3), or by another approved method, when the concentration of
that primary contaminant determined by the normal analytical routine
(Sect. 11.2) is > 80% of the established MCL, or action level, and the
required LFM analysis does not verify the absence of a matrix interference
(see Sects. 1.6&9.4).
11.2.9 Report data as directed in Section 12.
11.3 If the method of standard additions (MSA) is used, standards are added at one or
200.5-25
-------
more levels to portions of a prepared sample. This technique(9) compensates for
enhancement or depression of an analyte signal by a matrix. It will not correct for
additive interferences such as contamination, interelement interferences, or baseline
shifts. This technique is valid in the linear range when the interference effect is
constant over the range, the added analyte responds the same as the endogenous
analyte, and the signal is corrected for additive interferences. The simplest version
of this technique is the single-addition method. This procedure calls for two
identical aliquots of the sample solution to be taken. To the first aliquot, a small
volume of standard is added, while to the second aliquot, a volume of acid blank is
added equal to the standard addition. The sample concentration is calculated by the
following:
S2 x Vj x C
Sample Cone =
,ig/L (SrS2)xV
2
where: C = Concentration of the standard solution (|ig/L)
Sj = Signal for fortified aliquot
S2 = Signal for unfortified aliquot
Vj = Volume of the standard addition (L)
V2 = Volume of the sample aliquot (L) used for MSA
12.0 DATA ANALYSIS AND CALCULATIONS
12.1 Sample data for the water matrix elements (Ca, Mg and Na) and silica should be
reported in units of mg/L. For compliance monitoring, total recoverable trace
elements should be reported in the same units used to express the MCL or action
level. If there is no established MCL, the trace element should be reported in |ig/L.
12.2 For water matrix analytes, multiply the solution analyte concentrations by the
dilution factor, 0.5, and report the data with allowance for sample dilution when
analyte concentrations exceed 90% or more of the LDR upper limit, and in the case
of Na when the analytical range is exceeded. Round the data to the thousandth place
and report up to three significant figures. Do not report analyte concentrations
below the IDL.
12.3 For total recoverable trace element analytes, multiply solution analyte
concentrations by the dilution factor 0.5, round off the data values (|ig/L) to the
nearest tenths place and report analyte concentrations up to three significant figures.
For drinking water compliance monitoring, do not report data below the analyte
reporting limit calculated from the laboratory determined MDL data (see Sect.
9.2.5). Typical MDLs and calculated reporting limits are given in Table 4.
12.4 The QC data obtained during the analyses provide an indication of the quality of the
sample data and should be provided with the sample results.
200.5-26
-------
13.0 METHOD PERFORMANCE
13.1 Listed in Table 4 are typical single laboratory total recoverable MDLs for the
sample procedure given in Sections 11.1, followed by analysis using pneumatic
nebulization. They were determined for the recommended wavelengths using
simultaneous AVICP-AES and the operating conditions given in Table 3. The
MDLs were determined in reagent blank matrix (best case situation) fortified with
the respective analyte concentration also listed in Table 4.
13.2 Data obtained from single laboratory method testing are summarized in Tables 5 and
6. Table 5 lists precision (RSD) and average recovery data for SRM 1643c that was
analyzed along with the drinking water samples listed in Table 6. The drinking
water samples were prepared using the procedure given in Section 11.1. Table 6
lists data for 4 different tap water matrices (two well water supplies, one surface
water supply, and a home cistern supply). Five unfortified aliquots were prepared to
determine sample background concentrations and four aliquots for each LFM. For
primary and secondary contaminants, the LFMs were fortified to a concentration
equivalent to the respective analyte MCL. Data for the analysis of the water matrix
elements and silica are listed at the bottom of sample data sheet.
14.0 POLLUTION PREVENTION
14.1 Pollution prevention encompasses any technique that reduces or eliminates the
quantity or toxicity of waste at the point of generation. Numerous opportunities for
pollution prevention exist in laboratory operation. The EPA has established a
preferred hierarchy of environmental management techniques that places pollution
prevention as the management option of first choice. Whenever feasible, laboratory
personnel should use pollution prevention techniques to address their waste
generation (e.g., Sect. 7.7). When wastes cannot be feasibly reduced at the source,
the Agency recommends recycling as the next best option.
14.2 For information about pollution prevention that may be applicable to laboratories
and research institutions, consult Less is Better: Laboratory Chemical Management
for Waste Reduction., available from the American Chemical Society's Department
of Government Relations and Science Policy, 1155 16th StreetN.W., Washington
D.C. 20036, or on-line at http://membership.acs.org/c/ccs/pub_9.htm.
15.0 WASTE MANAGEMENT
15.1 The Environmental Protection Agency requires that laboratory waste management
practices be conducted consistent with all applicable rules and regulations. The
Agency urges laboratories to protect the air, water, and land by minimizing and
controlling all releases from hoods and bench operations, complying with the letter
and spirit of any sewer discharge permits and regulations, and by complying with all
solid and hazardous waste regulations, particularly the hazardous waste
identification rules and land disposal restrictions. For further information on waste
management consult The Waste Management Manual for Laboratory Personnel,
available from the American Chemical Society at the address listed in the
200.5-27
-------
Section 14.2.
16.0 REFERENCES
1. U.S. Environmental Protection Agency. Sample Preparation Procedure for
Spectrochemical Determination of Total Recoverable Elements - Method 200.2,
Revision 2.8, May 1994 (EPA-600/R-94/111).
2. U.S. Environmental Protection Agency. Determination of Trace Elements by
Stabilized Temperature Graphite Furnace Atomic Absorption - Method 200.9,
Revision 2.2, May 1994 (EPA-600/R-94/111).
3. Carcinogens - Working With Carcinogens, Department of Health, Education, and
Welfare, Public Health Service, Center for Disease Control, National Institute for
Occupational Safety and Health, Publication No. 77-206, Aug. 1977. Available from
the National Technical Information Service (NTIS) as PB-277256.
4. OSHA Safety and Health Standards, General Industry, (29 CFR 1910), Occupational
Safety and Health Administration, OSHA 2206, (Revised, January 1976).
5. Safety in Academic Chemistry Laboratories, American Chemical Society
Publication, Committee on Chemical Safety, 3rd Edition, 1979.
6. American Society for Testing and Materials. Standard Specification for Reagent
Water, Dl 193-77. Annual Book of ASTM Standards, Vol. 11.01. Philadelphia, PA,
1991.
7. Code of Federal Regulations 40, Ch. 1, Pt. 136 Appendix B.
8. Glaser, J.A.,D.L. Foerst, G.D. McKee, S.A. Quave, and W.L. Budde, "Trace
Analyses for Waste waters," Environ. Sci. Technol.. 15 (1981) 1426-1435.
9. Winefordner, J.D., Trace Analysis: Spectroscopic Methods for Elements, Chemical
Analysis, Vol. 46, pp. 41-42.
200.5-28
-------
17.0 TABLES. DIAGRAMS. FLOWCHARTS. AND VALIDATION DATA
TABLE 1. WAVELENGTHS, BACKGROUND CORRECTION LOCATIONS,
AND RECOMMENDED CALIBRATION
Analyte
Wavelength3
(nm)
Location
For BKGD.
Correction
(nm)
Calibrate
to
(mg/L)
Aluminum
Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Calcium
Chromium
Copper
Iron
Lead
Magnesium
Manganese
Nickel
Selenium
Silica (SiO2)
Silver
Sodium
Tin
Vanadium
Zinc
308.215
206.833x2
189.042x2
493.409
313.042
249.678x2
226.502x2
315.887
267.716
324.754
271.441
220.353x2
279.079
257.610
231.604x2
196.090x2
251.611
328.068
330.232
189.980
292.402
206.200
+0.033
-0.009
-0.009
+0.033
+0.033
+0.016
+0.016
+0.033
+0.033
+0.033
+0.033
+0.016
+0.033
+0.033
+0.016
-0.009
+0.033
+0.033
+0.033
-0.018
+0.033
+0.033
5
0.5
0.5
1
0.1
1
0.1
20
0.5
2
5
0.5
20
0.5
0.5
0.5
21.4
0.1
20
0.2
0.5
0.5
The wavelengths listed in the noted spectral order are recommended because of their
sensitivity and overall acceptability. Other wavelengths may be substituted if they can
provide the needed sensitivity and are treated with the same corrective techniques for
spectral interference (see Sect. 4.1).
Suggested concentration for instrument calibration. Other calibration limits in the linear
ranges may be used.
200.5-29
-------
TABLE 2. MIXED STANDARD SOLUTIONS
Solutiona Analytes
I As, Be, Cd, Pb, Sb, Se, V, and Zn
II Ba, Cr, Fe, Mn, Ni, Sn, and SiO2
III Al, Cu, Ca, Mg, and Na
IV Ag and B
See Section 7.8.1
TABLE 3. AXIALLY VIEWED INDUCTIVELY COUPLED PLASMA
INSTRUMENT OPERATING CONDITIONS
rf power 950 watts
Argon supply liquid argon
Argon pressure 60 psi
Coolant argon flow rate 20 L/min
Aerosol carrier argon
pressure 27 psi
flow rate 635 mL/min
Auxiliary (plasma)
argon flow rate 0.5 L/min
Sample uptake rate
controlled to 1.6 mL/min
200.5-30
-------
TABLE 4. DETECTION AND REPORTING LIMITS
ANALYTE
Ag
Al
As
B
Ba
Be
Ca
Cd
Cr
Cu
Fe
Mg
Mn
Na
Ni
Pb
Sb
Se
SiO2
Sn
V
Zn
INSTRUMENT^
DETECT. LIMIT
mg/L |ig/L
0.2
3
2
0.5
0.03
0.03
0.02
0.2
0.2
0.2
5
0.02
0.07
0.4
0.6
1
1
2
0.01
1
0.2
0.4
MDL
SPIKE
|ig/L
0.5
4.0
2.5
0.8
0.08
0.04
-
0.4
0.4
0.4
10
0.08
.
1.3
3.0
2.0
3.0
-
1.0
0.6
0.6
METHOD
DETECTION LIMIT
(MDL^ ^g/L
0.2
2.2
1.4
0.3
0.05
0.02
-
0.1
0.2
0.3
o o
J.J
0.06
.
0.6
1.1
0.9
1.3
-
0.5
0.2
0.4
CALCULATED00
REPORTING
LIMIT. ne/L
0.5
4.9
3.1
0.7
0.2
0.1
-
0.3
0.5
0.7
7.3
0.2
.
1.4
2.5
2.0
2.9
-
1.1
0.5
0.9
Instrument detection limits are used as reporting limits for matrix elements.
The listed calculated reporting limits have been rounded up to the tenths place to fully meet the
2.2 multiple criteria and to eliminate the listing of insignificant numbers. Because of rounding
up to the tenths place, the reporting limits listed for Ba and Be are multiples of 4 and 5 times
their respective MDLs.
200.5-31
-------
TABLE 5. SRM(1643c) PRECISION AND ACCURACY DATA
ANALYTE
NIST - 1643 c
CERTIFIED VALUE
ua/L
DETERMINED
CONC. STD.
ua/L DEV.
AVERAGE
RECOVERY
RSD
Ag
Al
As
B
Ba
Be
Cd
Cr
Cu
Fe
Mn
Ni
Pb
Se
V
Zn
2.21 ± 0.30
114.6 ± 5.1
82.1 ± 1.2
119.0 ± 1.4
49.6 ± 3.1
23.2 ± 2.2
12.2 ± 1.0
19.0 ± 0.6
22.3 ± 2.8
106.9 ± 3.0
35.1 ± 2.2
60.6 ± 7.3
35.3 ± 0.9
12.7 ± 0.7
31.4 ± 2.8
73.9 ± 0.9
2.1
125
83.7
114
49.2
22.5
11.9
18.0
22.9
106
34.5
57.4
34.4
11.9
28.3
74.4
0.82
5.1
1.9
0.5
0.52
0.33
0.13
0.21
0.74
2.8
0.4
0.58
1.2
0.7
0.15
0.52
95%
109%
102%
96%
99%
97%
98%
103%
99%
99%
98%
95%
97%
94%
93%
101%
3.9%
4.1%
2.2%
0.4%
1.0%
1.5%
1.1%
1.2%
3.2%
2.7%
1.2%
1.0%
3.5%
5.9%
0.5%
0.7%
ANALYTE
NIST-1643c
CERTIFIED VALUE
ma/L
DETERMINED
CONC. STD.
ma/L DEV.
AVERAGE
RECOVERY
RSD
Ca
Mg
Na
36.8 ±
9.45 ±
12.19 ±
1.4
0.27
0.36
37.0
9.61
12.6
0.32
0.16
0.09
101%
102%
103%
0.9%
1.6%
0.7%
200.5-32
-------
TABLE 6. TRACE ELEMENT PRECISION AND RECOVERY DATA
TAP WATER - REGION 5 SURFACE WATER SUPPLY
ANALYTE
SAMPLE
CONC. STD.
|ig/L DEV.
AVERAGE
Spike RECOVERY
|ig/L
RSD
Ag
Al
As
B
Ba
Be
Cd
Cr
Cu
Fe
Mn
Ni
Pb
Sb
Se
Sn
V
Zn
<0.5
18
<3.1
34.8
37.7
<0.1
<0.3
<0.5
3.3
<7.3
0.4
1.5
<2.5
<2.0
<2.9
<1.1
<0.5
5.6
1.3
-
0.9
0.4
-
.
_
0.09
_
0.01
0.1
.
-
-
_
-
0.1
100
200
10.0
100
2000
4.0
5.0
100
1000
300
50
100
15.0
6.0
50
50
50
2000
100
105
105
101
100
100
98
99
101
99
98
99
100
100
104
102
100
99
1.2
1.5
4.2
1.5
1.3
1.4
1.8
1.3
1.3
1.5
1.1
1.0
2.2
5.3
2.0
2.0
1.4
1.0
Sample concentration below the calculated reporting limit.
Analysis of Water Matrix Elements
Sample RSD
Analyte Cone. mg/L
Ca
Mg
Na
SiO2
34.6
9.64
26.4
5.23
1.4
1.6
2.9
1.6
200.5-33
-------
TABLE 6. TRACE ELEMENT PRECISION AND RECOVERY DATA (Cont'd.)
TAP WATER - REGION 5 WELL WATER SUPPLY
ANALYTE
SAMPLE
CONC. STD.
|ig/L DEV.
AVERAGE
Spike RECOVERY
|ig/L
RSD
Ag
Al
As
B
Ba
Be
Cd
Cr
Cu
Fe
Mn
Ni
Pb
Sb
Se
Sn
V
Zn
<0.5
<4.9
17.7
96.0
107
<0.1
<0.3
<0.5
<0.7
552
15.0
<1.4
<2.5
<2.0
<2.9
<1.1
<0.5
6.2
-
0.3
0.7
0.7
-
.
_
-
2.7
0.1
-
.
_
-
_
-
0.36
100
200
10.0
100
2000
4.0
5.0
100
1000
300
50
100
15.0
6.0
50
50
50
2000
97
103
101
102
97
97
96
93
98
103
95
94
97
97
101
102
95
95
1.2
1.1
1.2
0.9
1.0
1.4
1.9
1.3
1.1
1.1
1.1
1.3
4.7
7.4
1.2
1.2
1.3
1.5
Sample concentration below the calculated reporting limit.
Analysis of Water Matrix Elements
Sample RSD
Analyte Cone. mg/L
Ca
Mg
Na
SiO2
69.9
28.0
57.9
12.3
0.6
0.7
1.9
0.8
200.5-34
-------
TABLE 6. TRACE ELEMENT PRECISION AND RECOVERY DATA (Cont'd.)
TAP WATER - REGION 6 WELL WATER SUPPLY
ANALYTE
SAMPLE
CONC.
STD.
DEV.
AVERAGE
Spike RECOVERY
|ig/L
RSD
Ag
Al
As
B
Ba
Be
Cd
Cr
Cu
Fe
Mn
Ni
Pb
Sb
Se
Sn
V
Zn
<0.5
<4.9
<3.1
56.4
203
<0.1
<0.3
1.3
155
8.6
0.6
3.3
<2.5
<2.0
4.1
4.4
11.5
26.4
-
-
1.2
3.6
-
.
0.07
2.7
1.9
0.02
0.2
.
_
0.5
0.1
0.2
0.5
100
200
10.0
100
2000
4.0
5.0
100
1000
300
50
100
15.0
6.0
50
50
50
2000
100
102
101
104
100
102
96
96
100
96
97
98
105
98
100
102
98
98
1.2
1.6
2.3
1.4
1.4
1.4
1.9
1.1
1.3
1.7
1.3
1.4
2.5
3.6
1.1
1.0
1.4
1.4
Sample concentration below the calculated reporting limit.
Analysis of Water Matrix Elements
Sample RSD
Analyte Cone. mg/L
Ca
Mg
Na
SiO2
44.6
9.26
41.0
26.2
1.6
1.6
1.7
1.6
200.5-35
-------
TABLE 6. TRACE ELEMENT PRECISION AND RECOVERY DATA (Cont'd.)
TAP WATER - CISTERN WATER SUPPLY
ANALYTE
SAMPLE
CONC. STD.
|ig/L DEV.
AVERAGE
Spike RECOVERY
|ig/L
RSD
Ag
Al
As
B
Ba
Be
Cd
Cr
Cu
Fe
Mn
Ni
Pb
Sb
Se
Sn
V
Zn
<0.5
31.3
<3.1
6.6
3.3
<0.1
<0.3
<0.5
262
13
0.6
<1.4
<2.5
<2.0
<2.9
<1.1
<0.5
14.2
0.9
-
0.2
0.05
-
.
_
1.5
1.9
0.01
-
.
_
-
_
-
3.4
100
200
10.0
100
2000
4.0
5.0
100
1000
300
50
100
15.0
6.0
50
50
50
2000
98
104
102
100
98
96
94
95
99
95
94
95
101
103
95
95
97
95
1.2
1.7
7.8
1.2
1.4
1.2
1.1
1.1
1.7
1.3
1.2
1.7
1.6
3.2
1.2
1.6
1.3
1.2
Sample concentration below the calculated reporting limit.
Analysis of Water Matrix Elements
Sample RSD
Analyte Cone. mg/L
Ca
Mg
Na
SiO2
10.1
0.68
2.3
2.07
0.7
1.0
1.1
0.6
200.5-36
------- |