1、Designation: D 6919 09Standard 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 () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 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 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 It is the users responsibility to ensure the validity ofthese test methods for waters of untested matric
6、es.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility 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 hazards
7、statements specific to this test method, see 8.3.2. Referenced Documents2.1 ASTM Standards:2D 1129 Terminology Relating to WaterD 1193 Specification for Reagent WaterD 2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD 3370 Practices for Sampli
8、ng Water from Closed ConduitsD 3856 Guide for Good Laboratory Practices in Laborato-ries Engaged in Sampling and Analysis of WaterD 4210 Practice for Intralaboratory Quality Control Proce-dures and a Discussion on Reporting Low-Level Data3D 5810 Guide for Spiking into Aqueous SamplesD 5847 Practice
9、for Writing Quality Control Specificationsfor Standard Test Methods for Water AnalysisD 5905 Practice for the Preparation of Substitute Wastewa-ter3. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod, refer to Terminology D 1129.4. Summary of Test Method4.1 Inorganic cations
10、 and the ammonium cation, hereafterreferred to as ammonium, are determined by ion chromatog-raphy in water and wastewater samples from a fixed samplevolume, typically 1050 L. The cationic analytes are sepa-rated using a cation-exchange material, which is packed intoguard and analytical columns.Adilu
11、te acid solution is typicallyused as the eluent.4.1.1 The separated cations are detected by using conduc-tivity detection. To achieve sensitive conductivity detection, itis essential that the background signal arising from the eluenthave low baseline noise. One means to achieve low back-ground noise
12、 is to combine the conductivity detector with asuppressor device that will reduce the conductance of theeluent, hence background noise, and also transform the sepa-rated cations into their more conductive corresponding bases.44.1.2 Detection can also be achieved without chemicalsuppression, whereby
13、the difference between the equivalentionic conductance of the eluent and analyte cation is measureddirectly after the analytical column. This test method will1This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibility of Subcommittee D19.05 on Inorganic
14、 Constituentsin Water.Current edition approved May 15, 2009. Published May 2009. Originallyapproved in 2003. Last previous edition approved in 2003 as D 6919 03.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book o
15、f ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn. The last approved version of this historical standard is referencedon www.astm.org.4International Standard ISO 14911.1*A Summary of Changes section appears at the end of this standard.Copy
16、right ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.consider 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 integ
17、rator or appropriate computer-based data systemis typically used for data presentation.4.2 The cations are identified based on their retention timescompared to known standards. Quantification is accomplishedby measuring cation peak areas and comparing them to theareas generated from known standards.
18、 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 andammonium in water and wastewaters. Al
19、kali 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, ion chromatography provides a rel
20、atively 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 some low-molecular-weight organic ba
21、ses(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 alkanolamines.6.1.1 High concentrations
22、 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 levels of sample acidity, that i
23、s, 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 isrecommended that columns used for ana
24、lysis 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 capacity and can tolerate acid co
25、ncentrations up to 10mM H+(pH 2.0), such as the trademarked IC-Pak C/MDcolumn.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, detergents, glassware,
26、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 Ion Chromatography Appara
27、tus, 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 pressure of up to 4000 p
28、si.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 analytical column.The pur
29、pose 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 other, and from otherions t
30、hat 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 baseline.7.1.6 Conduct
31、ivity 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 presentingthe detector output
32、 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 AnalyticalReagents of the American Che
33、mical Society,5where 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 samples in plasticware.Sodi
34、um 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 types5Reagent Chemicals, American Chemical Society Specificat
35、ions, AmericanChemical Society, Washington, DC. For Suggestions on the testing of reagents notlisted by the American Chemical Society, see Annual Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention,
36、 Inc. (USPC), Rockville,MD.D6919092may be used, provided it is first 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,FIG. 1 Example Chromatogr
37、am 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 Nonchemically Suppressed Conductivity Detection
38、(Single-Column Indirect Conductivity Detection)D6919093measured as total organic carbon (TOC), may significantlyerode the performance of this method 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; Sup
39、pressed Conductivity Detection(1.0 M methanesulfonic acid)Carefully add 48.040 g ofconcentrated 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 handled with care
40、. 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. Dilute to the mar
41、k 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 thefree acid) to a
42、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 anappropriate 0.22 to 0
43、.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 are also suitable fo
44、r 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 water and diluteto 1
45、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 water and dilute to
46、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 sulfate hetpahydrate
47、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 standards used for analysi
48、s 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 solutions.9. Precautio
49、ns9.1 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 Preservation10.1 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 l
