ASTM D6919-03
(Test Method)Standard Test Method for Determination of Dissolved Alkali and Alkaline Earth Cations and Ammonium in Water and Wastewater by Ion Chromatography
Standard Test Method for Determination of Dissolved Alkali and Alkaline Earth Cations and Ammonium in Water and Wastewater by Ion Chromatography
SIGNIFICANCE AND USE
This method is applicable to the simultaneous determination of dissolved alkali and alkaline earth cations and ammonium in water and wastewaters. Alkali and alkaline earth cations are traditionally determined by using spectroscopic techniques, such as AAS or ICP; whereas ammonium can be measured by using a variety of wet chemical methods, including colorimetry, ammonia-selective electrode, and titrimetry. However, ion chromatography provides a relatively straightforward method for the simultaneous determination of cations, such as lithium, sodium, potassium, calcium, magnesium, and ammonium, in fewer than 20–30 min.
SCOPE
1.1 This test method is valid for the simultaneous determination of the inorganic alkali and alkaline earth cations, lithium, sodium, potassium, magnesium, and calcium, as well as the ammonium cation in reagent water, drinking water, and wastewaters by suppressed and nonsuppressed ion chromatography.
1.2 The anticipated range of the method is 0.05-200 mg/L. The specific concentration ranges tested for this method for each cation were as follows (measured in mg/L):Lithium0.4-10.0Sodium4.0-40.0Ammonium0.4-10.0Potassium1.2-20.0Magnesium2.4-20.0Calcium4.0-40.0
1.2.1 The upper limits may be extended by appropriate dilution or by the use of a smaller injection volume. In some cases, using a larger injection loop may extend the lower limits.
1.3 It is the user's responsibility to ensure the validity of these test methods for waters of untested matrices.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For hazards statements specific to this test method, see 8.3.
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Designation:D6919–03
Standard Test Method for
Determination of Dissolved Alkali and Alkaline Earth
Cations and Ammonium in Water and Wastewater by Ion
Chromatography
This standard is issued under the fixed designation D 6919; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope D 4210 Practice for Interlaboratory Quality Control Proce-
dures and Discussion on Reporting Low-Level Data
1.1 This test method is valid for the simultaneous determi-
D 5810 Guide for Spiking into Aqueous Samples
nation of the inorganic alkali and alkaline earth cations,
D 5847 Practice for the Writing of Quality Control Speci-
lithium, sodium, potassium, magnesium, and calcium, as well
fications for Standard Test Methods for Water Analysis
as the ammonium cation in reagent water, drinking water, and
D 5905 Practice for the Preparation of Substitute Wastewa-
wastewaters by suppressed and nonsuppressed ion chromatog-
ter
raphy.
1.2 The anticipated range of the method is 0.05–200 mg/L.
3. Terminology
The specific concentration ranges tested for this method for
3.1 Definitions—For definitions of terms used in this test
each cation were as follows (measured in mg/L):
method, refer to Terminology D 1129.
Lithium 0.4–10.0
Sodium 4.0–40.0
4. Summary of Test Method
Ammonium 0.4–10.0
Potassium 1.2–20.0
4.1 Inorganic cations and the ammonium cation, hereafter
Magnesium 2.4–20.0
referred to as ammonium, are determined by ion chromatog-
Calcium 4.0–40.0
raphy in water and wastewater samples from a fixed sample
1.2.1 The upper limits may be extended by appropriate
volume, typically 10–50 µL. The cationic analytes are sepa-
dilution or by the use of a smaller injection volume. In some
rated using a cation-exchange material, which is packed into
cases,usingalargerinjectionloopmayextendthelowerlimits.
guardandanalyticalcolumns.Adiluteacidsolutionistypically
1.3 It is the user’s responsibility to ensure the validity of
used as the eluent.
these test methods for waters of untested matrices.
4.1.1 The separated cations are detected by using conduc-
1.4 This standard does not purport to address all of the
tivity detection. To achieve sensitive conductivity detection, it
safety concerns, if any, associated with its use. It is the
is essential that the background signal arising from the eluent
responsibility of the user of this standard to establish appro-
have low baseline noise. One means to achieve low back-
priate safety and health practices and determine the applica-
ground noise is to combine the conductivity detector with a
bility of regulatory limitations prior to use. For hazards
suppressor device that will reduce the conductance of the
statements specific to this test method, see 8.3.
eluent, hence background noise, and also transform the sepa-
rated cations into their more conductive corresponding bases.
2. Referenced Documents
4.1.2 Detection can also be achieved without chemical
2.1 ASTM Standards:
suppression, whereby the difference between the equivalent
D 1129 Terminology Relating to Water
ionic conductance of the eluent and analyte cation is measured
D 1193 Specifications for Reagent Water
directly after the analytical column. This test method will
D 2777 Practice for Determination of Precision and Bias of
consider both suppressed and nonsuppressed detection tech-
Applicable Methods of Committee D19 on Water
nologies. The conductivity data is plotted to produce a chro-
D 3370 Practices for Sampling Water
matogram that is used to determine peak areas. A chromato-
D 3856 Guide for Good Laboratory Practices in Laborato-
graphic integrator or appropriate computer-based data system
ries Engaged in Sampling and Analysis of Water
is typically used for data presentation.
4.2 The cations are identified based on their retention times
1 compared to known standards. Quantification is accomplished
This test method is under the jurisdiction of ASTM Committee D19 on Water
and is the direct responsibility of Subcommittee D19.05 on Inorganic Constituents
in Water.
Current edition approved Aug. 10, 2003. Published September 2003.
2 3
Annual Book of ASTM Standards, Vol 11.01. International Standard ISO 14911.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D6919–03
by measuring cation peak areas and comparing them to the 7.1.1 Eluent Pump, capable of delivering 0.25–5 mL/min of
areas generated from known standards. The results are calcu- eluent at a pressure of up to 4000 psi.
lated using a standard curve based on peak areas of known 7.1.2 Injection Valve, a low dead-volume switching valve
concentrations of standards in reagent water. that allows the loading of a sample into a sample loop and
subsequent injection of the loop contents into the eluent
5. Significance and Use
stream.
5.1 This method is applicable to the simultaneous determi- 7.1.3 Guard Column, cation-exchange column typically
nation of dissolved alkali and alkaline earth cations and
packed with the same material used in the analytical column.
ammonium in water and wastewaters.Alkali and alkaline earth The purpose of this column is to protect the analytical column
cations are traditionally determined by using spectroscopic
from particulate matter and irreversibly retained material.
techniques, such as AAS or ICP; whereas ammonium can be 7.1.4 Analytical Column, separator column, packed with a
measured by using a variety of wet chemical methods, includ-
weak acid functionalized cation-exchange material, capable of
ing colorimetry, ammonia-selective electrode, and titrimetry. separating the ions of interest from each other, and from other
However, ion chromatography provides a relatively straight-
ions that commonly occur in the sample matrix. The chosen
forward method for the simultaneous determination of cations,
column must give separations equivalent to those shown in
such as lithium, sodium, potassium, calcium, magnesium, and Figs. 1 and 2.
ammonium, in fewer than 20–30 min.
7.1.5 Suppressor Device—If using the suppressed conduc-
tivity detection mode, the suppressor must provide peak-to-
6. Interferences
peak noise of <2 nS per minute of monitored baseline.
6.1 No individual interferences have been established, but it
7.1.6 Conductivity Detector, a low-volume, flow-through,
is possible that some low-molecular-weight organic bases
temperature-controlled (typically at 35°C) conductivity cell
(amines) may have similar retention times to analytes of
equipped with a meter capable of reading 0–1000 µS/cm on a
interest, particularly later-eluting solutes, such as potassium,
linear scale.
magnesium, and calcium. Potential interferences include
7.1.7 Data System, a chromatographic integrator or
amines such as mono-, di-, and trimethylamines; mono-, di-,
computer-based data system capable of graphically presenting
and triethylamines; and alkanolamines.
the detector output signal versus time, as well as presenting the
6.1.1 High concentrations of analyte cations can interfere
integrated peak areas.
with the determination of low concentrations of other analyte
8. Reagents and Materials
cationswithsimilarretentiontimes.Forinstance,highlevelsof
sodium can interfere with the determination of low levels of
8.1 Purity of Reagents—Reagent-grade chemicals shall be
ammonium (that is, at ratios >1000:1).
used in all tests. Unless otherwise indicated, all reagents shall
6.1.2 High levels of sample acidity, that is, low pH, can also
conform to the specifications of the Committee on Analytical
interfere with this analysis by overloading the column, leading
Reagents of the American Chemical Society, where such
to poor peak shape and loss of resolution. The pH at which the
specifications are available. Other grades may be used, pro-
chromatographic separation begins to exhibit poor peak shape
vided it is first ascertained that the reagent is of sufficiently
depends upon the ion-exchange capacity of the column. It is
high purity to permit its use without reducing the accuracy of
recommended that columns used for analysis of acidic samples
the determination.
in conjunction with the suppressed conductivity version of this
NOTE 1—Prepare all reagents, standards, and samples in plasticware.
method be able to tolerate acid concentrations up to 50 mM
Sodium will leach from glassware and bias the quantification of sodium.
+
H (pH 1.3), such as the IonPact CS16 column. The columns
8.2 Purity of Water—Unless otherwise indicated, references
used with nonsuppressed conductivity detection typically have
towatershallbeunderstoodtomeanreagentwaterconforming
lower capacity and can tolerate acid concentrations up to 10
+
to Specification D 1193, Type IA. Other reagent water types
mM H (pH 2.0), such as the IC-Paky C/MD column.
may be used, provided it is first ascertained that the water is of
6.2 A slight decrease or increase in eluent strength often
sufficiently high purity to permit its use without adversely
allows interferences to elute after or before the peak of
affecting the bias and precision of the determination. For
concern.
example, neutral organic compounds in the reagent water,
6.3 Sodium is a common contaminant from many sources
measured as total organic carbon (TOC), may significantly
such as fingers, water, detergents, glassware, and other inci-
erode the performance of this method over time. It is recom-
dental sources. As a precaution, the user of this method is
mended that reagent water with less than 10 ppb TOC be used
advised to wear plastic gloves and use plasticware for all
for all prepared solutions in this method.
solutions,standards,andpreparedsamples.Inaddition,method
8.3 Eluent Concentrate; Suppressed Conductivity Detection
blanks should be monitored for background sodium contami-
(1.0 M methanesulfonic acid)—Carefully add 48.040 g of
nation.
7. Apparatus
Reagent Chemicals, American Chemical Society Specifications,Am. Chemical
7.1 Ion Chromatography Apparatus,analyticalsystemcom-
Soc., Washington, DC. For suggestions on the testing of reagents not listed by the
plete with all required accessories, including eluent pump,
American Chemical Society, see Analar Standards for Laboratory Chemicals,by
injector, syringes, columns, suppressor (if used), conductivity
BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopoeia and National
detector, data system, and compressed gasses (if required). Formulary, U.S. Pharmacopeial Convention, Inc. (USPC) Rockville, MD.
D6919–03
FIG. 1 Example Chromatogram of Dissolved Alkali and Alkaline Earth Cations, and Ammonium by Ion Chromatography Using
Suppressed Conductivity Detection
FIG. 2 Example QC Standard Chromatogram of Dissolved Alkali and Alkaline Earth Cations, and Ammonium by Ion Chromatography
Using Nonchemically Suppressed Conductivity Detection (Single-Column Indirect Conductivity Detection)
D6919–03
TABLE 1 Instrument Conditions for the Analysis of Dissolved
concentratedmethanesulfonicacidtoapproximately400mLof
Alkali and Alkaline Earth Cations and Ammonium by Ion
water in a 500–mL volumetric flask. Dilute to the mark and
Chromatography Using Suppressed Conductivity Detection
mix thoroughly.
Eluent: 26 mM methanesulfonic acid
Flow rate: 1.5 mL/min
NOTE 2—Methanesulfonic acid is a corrosive, strong acid that should
Column: Dionex IonPac CG16/CS16
be handled with care. Always handle this reagent in a fume hood while
Sample Loop: 10 µL
wearing gloves and eye protection.
Detection: Suppressed conductivity
8.4 Eluent Analysis Solution; Suppressed Conductivity De- Suppressor: CSRS ULTRA
Background: ~2 µS
tection (26 mM methanesulfonic acid)—Add26.0mLofeluent
Solutes: 1 = lithium (1.0 mg/L), 2 = sodium (1.0 mg/L),
stock (8.3) to a 1–L plastic volumetric flask containing
3 = ammonium (1.0 mg/L), 4 = potassium (1.0 mg/L),
5 = magnesium (1.0 mg/L), 6 = calcium (1.0 mg/L)
approximately 500 mL of water. Dilute to the mark and mix
thoroughly. The eluent analysis solution must be filtered
throughanappropriate0.22–or0.45–µmfilteranddegassedby
vacuum sonication or helium sparging prior to use.
8.8 Blank—The blank standard is a portion of the water
8.5 Eluent Analysis Solution; Nonsuppressed Conductivity
used to prepare the cation working solutions.
Detection (3 mM nitric acid)—Add 29 mg of EDTA (as the
free acid) to a 1–Lplastic volumetric flask containing approxi- 9. Precautions
mately 500 mL of water. Using a magnetic stir bar, mix for 10
9.1 These methods address the determination of low con-
min. Add 30 mL of 100 mM nitric acid, or 189 µL of
centrations of cations.Accordingly, every precaution should be
concentrated nitric acid. Dilute to the mark and mix thor-
taken to ensure the cleanliness of sample containers, as well as
oughly.Theeluentanalysissolutionmustbefilteredthroughan
other materials and apparatus that come in contact with the
appropriate 0.22– to 0.45–µm filter and degassed by vacuum
sample.
sonication or helium sparging prior to use.
8.6 Standard Solutions, Stock (1000 mg/L)—Prepare all
10. Sampling and Sample Preservation
standard solutions in plasticware. It is recommended that the
10.1 CollectthesampleinaccordancewithPracticeD 3370,
user purchase certified stock standard solutions. Stock stan-
as applicable.
dards typically used for AAS are also suitable for the prepa-
10.2 Samplesmustbecollectedinplasticcontainersthatare
ration of cation working standards.
clean and free of artifacts and interferences. The suitability of
NOTE 3—Neutral pH cation standards are preferred. Alternatively, the containers must be demonstrated for each new lot by
prepare stock standard solutions from the following salts, as described
performing a container blank and laboratory fortified container
below:
blank.
10.3 Samplesthatwillnotbeanalyzedimmediatelymustbe
8.6.1 Ammonium Solution, Stock (1000 mg/L)—Dissolve
2.965 g of anhydrous ammonium chloride in water and dilute preserved with sulfuric acid to a pH of 2. Whereas samples to
+
be analyzed for cations are typically preserved with nitric acid,
to 1 L volumetrically; 1.00 mL = 1.00 mg NH .
8.6.2 Lithium Solution, Stock (1000 mg/L)—Dissolve 6.108 sulfuric acid is recommended for ammonium. Add 0.8 mL
concentrated H SO /L of sample and store at 4°C. The pH of
g of anhydrous lithium chloride in water and dilute to 1 L
2 4
+
volumetrically; 1.00 mL = 1.00 mg Li . samples preserved in this manner should be between 1.5 and 2,
although some wastewaters may require more conce
...
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