1、Designation: D 6919 03Standard Test Method forDetermination of Dissolved Alkali and Alkaline EarthCations and Ammonium in Water and Wastewater by IonChromatography1This standard is issued under the fixed designation D 6919; the number immediately following the designation indicates the year oforigin
2、al adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method is valid for the simultaneous determi-nation of
3、 the inorganic alkali and alkaline earth cations,lithium, sodium, potassium, magnesium, and calcium, as wellas the ammonium cation in reagent water, drinking water, andwastewaters by suppressed and nonsuppressed ion chromatog-raphy.1.2 The anticipated range of the method is 0.05200 mg/L.The specific
4、 concentration ranges tested for this method foreach cation were as follows (measured in mg/L):Lithium 0.410.0Sodium 4.040.0Ammonium 0.410.0Potassium 1.220.0Magnesium 2.420.0Calcium 4.040.01.2.1 The upper limits may be extended by appropriatedilution or by the use of a smaller injection volume. In s
5、omecases, using a larger injection loop may extend the lower limits.1.3 It is the users responsibility to ensure the validity ofthese test methods for waters of untested matrices.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is therespon
6、sibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. For hazardsstatements specific to this test method, see 8.3.2. Referenced Documents2.1 ASTM Standards:D 1129 Terminology Relating to Wa
7、ter2D 1193 Specifications for Reagent Water2D 2777 Practice for Determination of Precision and Bias ofApplicable Methods of Committee D19 on Water2D 3370 Practices for Sampling Water2D 3856 Guide for Good Laboratory Practices in Laborato-ries Engaged in Sampling and Analysis of Water2D 4210 Practice
8、 for Interlaboratory Quality Control Proce-dures and Discussion on Reporting Low-Level Data2D 5810 Guide for Spiking into Aqueous Samples2D 5847 Practice for the Writing of Quality Control Speci-fications for Standard Test Methods for Water Analysis2D 5905 Practice for the Preparation of Substitute
9、Wastewa-ter23. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod, refer to Terminology D 1129.4. Summary of Test Method4.1 Inorganic cations and the ammonium cation, hereafterreferred to as ammonium, are determined by ion chromatog-raphy in water and wastewater samples from
10、a fixed samplevolume, typically 1050 L. The cationic analytes are sepa-rated using a cation-exchange material, which is packed intoguard and analytical columns.Adilute acid solution is typicallyused as the eluent.4.1.1 The separated cations are detected by using conduc-tivity detection. To achieve s
11、ensitive conductivity detection, itis essential that the background signal arising from the eluenthave low baseline noise. One means to achieve low back-ground noise is to combine the conductivity detector with asuppressor device that will reduce the conductance of theeluent, hence background noise,
12、 and also transform the sepa-rated cations into their more conductive corresponding bases.34.1.2 Detection can also be achieved without chemicalsuppression, whereby the difference between the equivalentionic conductance of the eluent and analyte cation is measureddirectly after the analytical column
13、. This test method willconsider both suppressed and nonsuppressed detection tech-nologies. The conductivity data is plotted to produce a chro-matogram that is used to determine peak areas. A chromato-graphic integrator or appropriate computer-based data systemis typically used for data presentation.
14、4.2 The cations are identified based on their retention timescompared to known standards. Quantification is accomplished1This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibility of Subcommittee D19.05 on Inorganic Constituentsin Water.Current edition
15、approved Aug. 10, 2003. Published September 2003.2Annual Book of ASTM Standards, Vol 11.01.3International Standard ISO 14911.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.by measuring cation peak areas and comparing them to thearea
16、s generated from known standards. The results are calcu-lated using a standard curve based on peak areas of knownconcentrations of standards in reagent water.5. Significance and Use5.1 This method is applicable to the simultaneous determi-nation of dissolved alkali and alkaline earth cations andammo
17、nium in water and wastewaters. Alkali and alkaline earthcations are traditionally determined by using spectroscopictechniques, such as AAS or ICP; whereas ammonium can bemeasured by using a variety of wet chemical methods, includ-ing colorimetry, ammonia-selective electrode, and titrimetry.However,
18、ion chromatography provides a relatively straight-forward method for the simultaneous determination of cations,such as lithium, sodium, potassium, calcium, magnesium, andammonium, in fewer than 2030 min.6. Interferences6.1 No individual interferences have been established, but itis possible that som
19、e low-molecular-weight organic bases(amines) may have similar retention times to analytes ofinterest, particularly later-eluting solutes, such as potassium,magnesium, and calcium. Potential interferences includeamines such as mono-, di-, and trimethylamines; mono-, di-,and triethylamines; and alkano
20、lamines.6.1.1 High concentrations of analyte cations can interferewith the determination of low concentrations of other analytecations with similar retention times. For instance, high levels ofsodium can interfere with the determination of low levels ofammonium (that is, at ratios 1000:1).6.1.2 High
21、 levels of sample acidity, that is, low pH, can alsointerfere with this analysis by overloading the column, leadingto poor peak shape and loss of resolution. The pH at which thechromatographic separation begins to exhibit poor peak shapedepends upon the ion-exchange capacity of the column. It isreco
22、mmended that columns used for analysis of acidic samplesin conjunction with the suppressed conductivity version of thismethod be able to tolerate acid concentrations up to 50 mMH+(pH 1.3), such as the IonPact CS16 column. The columnsused with nonsuppressed conductivity detection typically havelower
23、capacity and can tolerate acid concentrations up to 10mM H+(pH 2.0), such as the IC-Paky C/MD column.6.2 A slight decrease or increase in eluent strength oftenallows interferences to elute after or before the peak ofconcern.6.3 Sodium is a common contaminant from many sourcessuch as fingers, water,
24、detergents, glassware, and other inci-dental sources. As a precaution, the user of this method isadvised to wear plastic gloves and use plasticware for allsolutions, standards, and prepared samples. In addition, methodblanks should be monitored for background sodium contami-nation.7. Apparatus7.1 Io
25、n Chromatography Apparatus, analytical system com-plete with all required accessories, including eluent pump,injector, syringes, columns, suppressor (if used), conductivitydetector, data system, and compressed gasses (if required).7.1.1 Eluent Pump, capable of delivering 0.255 mL/min ofeluent at a p
26、ressure of up to 4000 psi.7.1.2 Injection Valve, a low dead-volume switching valvethat allows the loading of a sample into a sample loop andsubsequent injection of the loop contents into the eluentstream.7.1.3 Guard Column, cation-exchange column typicallypacked with the same material used in the an
27、alytical column.The purpose of this column is to protect the analytical columnfrom particulate matter and irreversibly retained material.7.1.4 Analytical Column, separator column, packed with aweak acid functionalized cation-exchange material, capable ofseparating the ions of interest from each othe
28、r, and from otherions that commonly occur in the sample matrix. The chosencolumn must give separations equivalent to those shown inFigs. 1 and 2.7.1.5 Suppressor DeviceIf using the suppressed conduc-tivity detection mode, the suppressor must provide peak-to-peak noise of 2 nS per minute of monitored
29、 baseline.7.1.6 Conductivity Detector, a low-volume, flow-through,temperature-controlled (typically at 35C) conductivity cellequipped with a meter capable of reading 01000 S/cm on alinear scale.7.1.7 Data System, a chromatographic integrator orcomputer-based data system capable of graphically presen
30、tingthe detector output signal versus time, as well as presenting theintegrated peak areas.8. Reagents and Materials8.1 Purity of ReagentsReagent-grade chemicals shall beused in all tests. Unless otherwise indicated, all reagents shallconform to the specifications of the Committee on AnalyticalReage
31、nts of the American Chemical Society,4where suchspecifications are available. Other grades may be used, pro-vided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without reducing the accuracy ofthe determination.NOTE 1Prepare all reagents, standards, and samp
32、les in plasticware.Sodium will leach from glassware and bias the quantification of sodium.8.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent water conformingto Specification D 1193, Type IA. Other reagent water typesmay be used, provided it is first
33、 ascertained that the water is ofsufficiently high purity to permit its use without adverselyaffecting the bias and precision of the determination. Forexample, neutral organic compounds in the reagent water,measured as total organic carbon (TOC), may significantlyerode the performance of this method
34、 over time. It is recom-mended that reagent water with less than 10 ppb TOC be usedfor all prepared solutions in this method.8.3 Eluent Concentrate; Suppressed Conductivity Detection(1.0 M methanesulfonic acid)Carefully add 48.040 g of4Reagent Chemicals, American Chemical Society Specifications, Am.
35、 ChemicalSoc., Washington, DC. For suggestions on the testing of reagents not listed by theAmerican Chemical Society, see Analar Standards for Laboratory Chemicals,byBDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopoeia and NationalFormulary, U.S. Pharmacopeial Convention, Inc. (USPC) R
36、ockville, MD.D6919032FIG. 1 Example Chromatogram of Dissolved Alkali and Alkaline Earth Cations, and Ammonium by Ion Chromatography UsingSuppressed Conductivity DetectionFIG. 2 Example QC Standard Chromatogram of Dissolved Alkali and Alkaline Earth Cations, and Ammonium by Ion ChromatographyUsing No
37、nchemically Suppressed Conductivity Detection (Single-Column Indirect Conductivity Detection)D6919033concentrated methanesulfonic acid to approximately 400 mLofwater in a 500mL volumetric flask. Dilute to the mark andmix thoroughly.NOTE 2Methanesulfonic acid is a corrosive, strong acid that shouldbe
38、 handled with care. Always handle this reagent in a fume hood whilewearing gloves and eye protection.8.4 Eluent Analysis Solution; Suppressed Conductivity De-tection (26 mM methanesulfonic acid)Add 26.0 mL of eluentstock (8.3) to a 1L plastic volumetric flask containingapproximately 500 mL of water.
39、 Dilute to the mark and mixthoroughly. The eluent analysis solution must be filteredthrough an appropriate 0.22 or 0.45m filter and degassed byvacuum sonication or helium sparging prior to use.8.5 Eluent Analysis Solution; Nonsuppressed ConductivityDetection (3 mM nitric acid)Add 29 mg of EDTA (as t
40、hefree acid) to a 1L plastic volumetric flask containing approxi-mately 500 mL of water. Using a magnetic stir bar, mix for 10min. Add 30 mL of 100 mM nitric acid, or 189 L ofconcentrated nitric acid. Dilute to the mark and mix thor-oughly. The eluent analysis solution must be filtered through anapp
41、ropriate 0.22 to 0.45m filter and degassed by vacuumsonication or helium sparging prior to use.8.6 Standard Solutions, Stock (1000 mg/L)Prepare allstandard solutions in plasticware. It is recommended that theuser purchase certified stock standard solutions. Stock stan-dards typically used for AAS ar
42、e also suitable for the prepa-ration of cation working standards.NOTE 3Neutral pH cation standards are preferred. Alternatively,prepare stock standard solutions from the following salts, as describedbelow:8.6.1 Ammonium Solution, Stock (1000 mg/L)Dissolve2.965 g of anhydrous ammonium chloride in wat
43、er and diluteto 1 L volumetrically; 1.00 mL = 1.00 mg NH4+.8.6.2 Lithium Solution, Stock (1000 mg/L)Dissolve 6.108g of anhydrous lithium chloride in water and dilute to 1 Lvolumetrically; 1.00 mL = 1.00 mg Li+.8.6.3 Sodium Solution, Stock (1000 mg/L)Dissolve 2.541g of anhydrous sodium chloride in wa
44、ter and dilute to 1 Lvolumetrically; 1.00 mL = 1.00 mg Na+.8.6.4 Potassium Solution, Stock (1000 mg/L)Dissolve3.481 g of anhydrous potassium phosphate monobasic in waterand dilute to 1 L volumetrically; 1.00 mL = 1.00 mg K+.8.6.5 Magnesium Solution, Stock (1000 mg/L)Dissolve10.144 g of magnesium sul
45、fate hetpahydrate in water anddilute to 1 L volumetrically; 1.00 mL = 1.00 mg Mg2+.8.6.6 Calcium Solution, Stock (1000 mg/L)Dissolve 3.668g of calcium chloride dihydrate in water and dilute to 1 Lvolumetrically; 1.00 mL = 1.00 mg Ca2+.8.7 Cation Working StandardsAll calibration standardsand standard
46、s used for analysis should be prepared in 100mLvolumetric flasks, as described below.Standard concentration mg/L!5stock volume added mL! 1000 mg/L!100 mL!Example:10 mg/L Na 51 mL Na stock 1000 mg/L Na!100 mL!8.8 BlankThe blank standard is a portion of the waterused to prepare the cation working solu
47、tions.9. Precautions9.1 These methods address the determination of low con-centrations of cations.Accordingly, every precaution should betaken to ensure the cleanliness of sample containers, as well asother materials and apparatus that come in contact with thesample.10. Sampling and Sample Preservat
48、ion10.1 Collect the sample in accordance with Practice D 3370,as applicable.10.2 Samples must be collected in plastic containers that areclean and free of artifacts and interferences. The suitability ofthe containers must be demonstrated for each new lot byperforming a container blank and laboratory
49、 fortified containerblank.10.3 Samples that will not be analyzed immediately must bepreserved with sulfuric acid to a pH of 2. Whereas samples tobe analyzed for cations are typically preserved with nitric acid,sulfuric acid is recommended for ammonium.5Add 0.8 mLconcentrated H2SO4/L of sample and store at 4C. The pH ofsamples preserved in this manner should be between 1.5 and 2,although some wastewaters may require more concentratedH2SO4to achieve this pH. This pH increases the holding timeto 28 days.11. Preparation of Apparatus11.1
