1、Designation: D4191 15Standard Test Method forSodium in Water by Atomic Absorption Spectrophotometry1This standard is issued under the fixed designation D4191; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revisio
2、n. 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 covers the determination of lowamounts of sodium in waters2having low solids content. Theapplicable range of thi
3、s test method is from 0.20 to 3.0 mg/Lwhen using the 589.6-nm resonance line. This range may beextended upward by dilution of an appropriate aliquot ofsample or by use of the less-sensitive 330.2-nm resonance line(see Test Method D3561). Many workers have found that thistest method is reliable for s
4、odium levels to 0.005 mg/L, but useof this test method at this low level is dependent on theconfiguration of the aspirator and nebulizer system available inthe atomic absorption spectrophotometer as well as the expe-rience and skill of the analyst. The precision and bias datapresented are insufficie
5、nt to justify use of this test method inthe 0.005 to 0.20-mg/L range.1.2 This test method has been used successfully with spikedreagent water. It is the analysts responsibility to assure thevalidity of the test method to other low dissolved solidsmatrices.1.3 The values stated in SI units are to be
6、regarded asstandard. The values given in parentheses are mathematicalconversions to inch-pound units that are provided for informa-tion only and are not considered standard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibili
7、ty 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.2. Referenced Documents2.1 ASTM Standards:3D1066 Practice for Sampling SteamD1129 Terminology Relating to WaterD1193 Specification for Reagent
8、 WaterD2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD3370 Practices for Sampling Water from Closed ConduitsD3561 Test Method for Lithium, Potassium, and SodiumIons in Brackish Water, Seawater, and Brines by AtomicAbsorption Spectrophotometr
9、yD4841 Practice for Estimation of Holding Time for WaterSamples Containing Organic and Inorganic ConstituentsD5810 Guide for Spiking into Aqueous SamplesD5847 Practice for Writing Quality Control Specificationsfor Standard Test Methods for Water Analysis3. Terminology3.1 DefinitionsFor definitions o
10、f terms used in this testmethod, refer to Terminology D1129.4. Summary of Test Method4.1 Sodium is determined by flame atomic absorption spec-trophotometry. The sodium content is determined by aspiratingthe low solids sample directly with no sample pretreatment.5. Significance and Use5.1 Sodium salt
11、s are very soluble, and sodium leached fromsoil and rocks tends to remain in solution. Water with a highratio of sodium to calcium is deleterious to soil structure.5.2 Sodium is not particularly significant in potable waterexcept for those persons having an abnormal sodiummetabolism, but water suppl
12、ies in some areas contain sufficientsodium to be a factor in the planning of sodium-free diets.5.3 The use of sodium salts is common in industry;therefore, many industrial wastewaters contain significantquantities of sodium. For high-pressure boiler feed-water eventrace amounts of sodium are of conc
13、ern.6. Interferences6.1 In the analysis of low-solids water, interferences areusually negligible.7. Apparatus7.1 Atomic Absorption Spectrophotometer for use at 589.6nm.1This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibility of Subcommittee D19.05 on
14、 Inorganic Constituentsin Water.Current edition approved Feb. 1, 2015. Published March 2015. Originallyapproved in 1982. Last previous edition approved in 2008 as D4191 08. DOI:10.1520/D4191-15.2Platte, J.A., and Marcy, V. M., “ANew Tool for the Water Chemist,” IndustrialWater Engineering, May 1965.
15、3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.*A Summary of Changes section appears at the end of this stan
16、dardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1NOTE 1The manufacturers instructions should be followed for allinstrumental parameters. Wavelengths other than 589.6 nm may be usedonly if they have been determined to be equally sui
17、table.7.2 Sodium Hollow-Cathode LampsMultielement hollowcathode lamps are available and also have been found satis-factory.7.3 Pressure-Reducing ValvesThe supplies of fuel andoxidant shall be maintained at pressures somewhat higher thanthe operating pressure of the instrument by using suitablevalves
18、.8. Reagents8.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Societywhere such specifications are available.4Other
19、 grades may beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.8.2 Purity of WaterUnless otherwise indicated, referenceto water shall be understood to mean reagent water conformingto Specificati
20、on D1193, Type I. Other reagent water types maybe 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 test method. Type IIwater was specified at the time of round robin testing of thistest metho
21、d.8.3 Sodium Solution, Stock (1.0 mL = 1.0 mg Na)Commercially purchase or dry sodium chloride to constantweight at 105C. Dissolve 2.5418 g of the dry sodium chloride(NaCl) in water and dilute to 1 L with water.NOTE 2Certified sodium stock solutions of appropriate known purityare commercially availab
22、le through chemical supply vendors.8.4 Sodium Solution, Standard (1.00 mL = 0.1 mg Na)Dilute 100.0 mL of sodium stock solution to 1 L with water.8.5 Oxidant: Air, which has been passed through a suitablefilter to remove oil, water, and other foreign substances is theusual oxidant.8.6 Fuel: Acetylene
23、Standard, commercially availableacetylene is the usual fuel. Acetone, always present in acety-lene cylinders can affect analytical results. The cylinder shouldbe replaced at 345 kPa (50 psi) to avoid acetone carryover.8.6.1 Warning“Purified” grade acetylene containing aspecial proprietary solvent ra
24、ther than acetone should not beused with poly(vinyl chloride) tubing as weakening of thetubing walls can cause a potentially dangerous situation.9. Sampling9.1 Collect the samples in accordance with the applicableASTM test method as follows: Practices D3370 and PracticeD1066.10. Standardization10.1
25、Prepare 100 mL each of a blank and at least fourstandard solutions to bracket the expected sodium concentra-tion range of the samples to be analyzed by diluting thestandard sodium solution (8.4) with water. Prepare the stan-dards each time the test is to be performed or as determined byPractice D484
26、1. Select the standards to give zero, middle, andmaximum points for an analytical curve.10.2 Analyze at least four working standards containingconcentrations of sodium that bracket the expected sampleconcentration, prior to analysis of samples, to calibrate theinstrument. Aspirate the blank and the
27、standards and record theinstrument readings. Aspirate water between standards.10.3 Read directly in concentration if this capability isprovided with the instrument or prepare an analytical curve byplotting the absorbance versus concentration for each standardon linear graph paper.11. Procedure11.1 A
28、spirate each sample and determine its absorbance orconcentration. Aspirate water between samples.12. Calculation12.1 Calculate the concentration of sodium in the samples,in milligrams per litre, by either referring the absorbanceobtained for each sample by reading directly in concentrationif the cap
29、ability is provided with the instrument, or prepared ananalytical curve (10.3).12.2 If an aliquot of diluted sample was analyzed, multiplythe concentration of sodium, in milligrams per litre, by theappropriate dilution factor.13. Precision and Bias513.1 The overall and single-operator precision of t
30、his testmethod for eight laboratories, which include a total of twelveoperators analyzing each sample on three consecutive days,within its range for reagent water varies with the quantity beingmeasured according to Table 1.NOTE 3Only reagent water was used to obtain the precision statementsince this
31、 test method is designated for the determination of low amountsof sodium in low-solids water.13.2 Recoveries of known amounts of sodium (from sodiumchloride) in the series of prepared standards for the samelaboratories and operators were as given in Table 1.4Reagent Chemicals, American Chemical Soci
32、ety Specifications, 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. Pharmacopei
33、al Convention, Inc. (USPC), Rockville,MD.5Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D19-1080. ContactASTM CustomerService at serviceastm.org.TABLE 1 Determination of Bias for Sodium in Reagent Water byAtomic AbsorptionAmoun
34、tAdded,mg/LAmountFound,mg/LStSoBias %0.20 0.184 0.053 0.024 8.01.20 1.25 0.094 0.028 + 4.172.70 2.81 0.129 0.081 + 4.07D4191 15213.3 Precision and bias for this test method conforms toPractice D2777 77, which was in place at the time ofcollaborative testing. Under the allowances made in 1.4 ofPracti
35、ce D2777 13, these precision and bias data do meetexisting requirements for interlaboratory studies of CommitteeD19 test methods.14. Quality Control14.1 In order to be certain that analytical values obtainedusing these test methods are valid and accurate within theconfidence limits of the test, the
36、following QC procedures mustbe followed when analyzing sodium.14.2 Calibration and Calibration Verification:14.2.1 Analyze at least four working standards containingconcentrations of sodium that bracket the expected sampleconcentration, prior to analysis of samples, to calibrate theinstrument (see 1
37、0.2). The calibration correlation coefficientshall be equal to or greater than 0.990.14.2.2 Verify instrument calibration after standardization byanalyzing a standard at the concentration of one of thecalibration standards. The concentration of a mid-range stan-dard should fall within 615 % of the k
38、nown concentration.Analyze a calibration blank to verify system cleanliness.14.2.3 If calibration cannot be verified, recalibrate theinstrument.14.2.4 It is recommended to analyze a continuing calibra-tion blank (CCB) and continuing calibration verification(CCV) at a 10 % frequency. The results shou
39、ld fall within theexpected precision of the method or 615 % of the knownconcentration.14.3 Initial Demonstration of Laboratory Capability:14.3.1 If a laboratory has not performed the test before, or ifthere has been a major change in the measurement system, forexample, new analyst, new instrument, e
40、tc., a precision andbias study must be performed to demonstrate laboratorycapability.14.3.2 Analyze seven replicates of a standard solutionprepared from an Independent Reference Material containing amid-range concentration of sodium. The matrix and chemistryof the solution should be equivalent to th
41、e solution used in thecollaborative study. Each replicate must be taken through thecomplete analytical test method including any sample preser-vation and pretreatment steps.14.3.3 Calculate the mean and standard deviation of theseven values and compare to the acceptable ranges of bias inTable 1. Thi
42、s study should be repeated until the recoveries arewithin the limits given in Table 1. If a concentration other thanthe recommended concentration is used, refer to PracticeD5847 for information on applying the F test and t test inevaluating the acceptability of the mean and standard devia-tion.14.4
43、Laboratory Control Sample (LCS):14.4.1 To ensure that the test method is in control, analyzea LCS containing a known concentration of sodium with eachbatch (laboratory-defined or twenty samples). The laboratorycontrol samples for a large batch should cover the analyticalrange when possible. The LCS
44、must be taken through all of thesteps of the analytical method including sample preservationand pretreatment. The result obtained for a mid-range LCSshall fall within 615 % of the known concentration.14.4.2 If the result is not within these limits, analysis ofsamples is halted until the problem is c
45、orrected, and either allthe samples in the batch must be reanalyzed, or the results mustbe qualified with an indication that they do not fall within theperformance criteria of the test method.14.5 Method Blank:14.5.1 Analyze a reagent water test blank with eachlaboratory-defined batch. The concentra
46、tion of sodium foundin the blank should be less than 0.5 times the lowest calibrationstandard. If the concentration of sodium is found above thislevel, analysis of samples is halted until the contamination iseliminated, and a blank shows no contamination at or abovethis level, or the results must be
47、 qualified with an indicationthat they do not fall within the performance criteria of the testmethod.14.6 Matrix Spike (MS):14.6.1 To check for interferences in the specific matrixbeing tested, perform a MS on at least one sample from eachlaboratory-defined batch by spiking an aliquot of the samplew
48、ith a known concentration of sodium and taking it through theanalytical method.14.6.2 The spike concentration plus the background concen-tration of sodium must not exceed the high calibration stan-dard. The spike must produce a concentration in the spikedsample that is 2 to 5 times the analyte conce
49、ntration in theunspiked sample, or 10 to 50 times the detection limit of thetest method, whichever is greater.14.6.3 Calculate the percent recovery of the spike (P) usingthe following formula:P 5 100AVs1V! 2 BVs#/CV (1)where:A = analyte known concentration (mg/L) in spiked sample,B = analyte known concentration (mg/L) in unspikedsample,C = known concentration (mg/L) of analyte in spikingsolution,Vs= volume (mL) of sample used, andV = volume (mL) of spiking solution added.14.6.4 The percent recovery of the spike shall fall within thelimits, based on the analyte
