1、Designation: D 4191 08Standard Test Method forSodium in Water by Atomic Absorption Spectrophotometry1This standard is issued under the fixed designation D 4191; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revis
2、ion. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of lowamounts of sodium in waters2having low solids content. Theapplicable range of th
3、is 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 D 3561). Many workers have found that thistest method is reliable for
4、 sodium 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 insuffic
5、ient 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 b
6、e regarded asstandard. No other units of measurement are included in thisstandard.1.4 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 d
7、etermine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:D 1066 Practice for Sampling SteamD 1129 Terminology Relating to WaterD 1193 Specification for Reagent WaterD 2777 Practice for Determination of Precision and Bias ofApplicable Test Methods o
8、f Committee D19 on WaterD 3370 Practices for Sampling Water from Closed ConduitsD 3561 Test Method for Lithium, Potassium, and SodiumIons in Brackish Water, Seawater, and Brines by AtomicAbsorption SpectrophotometryD 5810 Guide for Spiking into Aqueous SamplesD 5847 Practice for Writing Quality Cont
9、rol Specificationsfor Standard Test Methods for Water Analysis3. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod, refer to Terminology D 1129.4. Summary of Test Method4.1 Sodium is determined by flame atomic absorption spec-trophotometry. The sodium content is determined b
10、y aspiratingthe low solids sample directly with no sample pretreatment.5. Significance and Use5.1 Sodium salts 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 particula
11、rly significant in potable waterexcept for those persons having an abnormal sodium metabo-lism, but water supplies 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; there-fore, many industrial wastewaters con
12、tain significant quantitiesof sodium. For high-pressure boiler feed-water even traceamounts of sodium are of concern.6. Interferences6.1 In the analysis of low-solids water, interferences areusually negligible.7. Apparatus7.1 Atomic Absorption Spectrophotometer for use at 589.6nm.NOTE 1The manufactu
13、rers instructions should be followed for allinstrumental parameters. Wavelengths other than 589.6 nm may be usedonly if they have been determined to be equally suitable.7.2 Sodium Hollow-Cathode LampsMultielement hollowcathode lamps are available and also have been found satis-factory.1This test met
14、hod is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibility of Subcommittee D19.05 on Inorganic Constituentsin Water.Current edition approved Oct. 1, 2008. Published October 2008. Originallyapproved in 1982. Last previous edition approved in 2003 as D 4191 03.2Platte
15、, J. A., and Marcy, V. M., “A New Tool for the Water Chemist,” IndustrialWater Engineering, May 1965 .1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.7.3 Oxidant: Air, which has been passed through a suitablefilter to remove oil, wat
16、er, and other foreign substances is theusual oxidant.7.4 Fuel: AcetyleneStandard, commercially availableacetylene is the usual fuel. Acetone, always present in acety-lene cylinders can affect analytical results. The cylinder shouldbe replaced at 50 psig (345 kPa) to avoid acetone carryover.7.4.1 War
17、ning: “Purified” grade acetylene containing aspecial proprietary solvent rather than acetone should not beused with poly(vinyl chloride) tubing as weakening of thetubing walls can cause a potentially hazardous situation.7.5 Pressure-Reducing ValvesThe supplies of fuel andoxidant shall be maintained
18、at pressures somewhat higher thanthe operating pressure of the instrument by using suitablevalves.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 A
19、nalytical Reagents of the American Chemical Societywhere such specifications are available.3Other 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 otherwis
20、e indicated, referenceto water shall be understood to mean reagent water conformingto Specification D 1193, 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 o
21、f the test method. Type IIwater was specified at the time of round robin testing of thistest method.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 wit
22、h water.NOTE 2Certified sodium stock solutions are commercially availablethrough 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.9. Sampling9.1 Collect the samples in accordance with the applicableASTM test method
23、as follows: Practices D 3370 and PracticeD 1066.10. Standardization10.1 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-dard
24、s each time the test is to be performed. Select the standardsto give zero, middle, and maximum points for an analyticalcurve.10.2 Aspirate the blank and the standards and record theinstrument readings. Aspirate water between standards.10.3 Prepare an analytical curve by plotting the absorbanceversus
25、 concentration for each standard on linear graph paper.Alternatively, read directly in concentration if this capability isprovided with the instrument.11. Procedure11.1 Aspirate each sample and determine its absorbance orconcentration. Aspirate water between samples.12. Calculation12.1 Calculate the
26、 concentration of sodium in the samples,in milligrams per litre, by either referring the absorbanceobtained for each sample to a prepared analytical curve (10.3)or reading directly in concentration if the capability is providedwith the instrument.12.2 If an aliquot of diluted sample was analyzed, mu
27、ltiplythe concentration of sodium, in milligrams per litre, by theappropriate dilution factor.13. Precision and Bias413.1 The overall and single-operator precision of this testmethod for eight laboratories, which include a total of twelveoperators analyzing each sample on three consecutive days,with
28、in 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 test method is designated for the determination of low amountsof sodium in low-solids water.13.2 Recoveries of known amounts of sod
29、ium (from sodiumchloride) in the series of prepared standards for the samelaboratories and operators were as given in Table 1.13.3 Precision and bias for this test method conforms toPractice D 2777 77, which was in place at the time ofcollaborative testing. Under the allowances made in 1.4 ofPractic
30、e D 2777 06, 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 the3Reagent Chemicals, American Chemic
31、al Society 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. Phar
32、macopeial Convention, Inc. (USPC), Rockville,MD.4Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR: D19-1080.TABLE 1 Determination of Bias for Sodium in Reagent Water byAtomic AbsorptionAmountAdded,mg/LAmountFound,mg/LStSoBias %0.2
33、0 0.184 0.053 0.024 8.01.20 1.25 0.094 0.028 + 4.172.70 2.81 0.129 0.081 + 4.07D4191082confidence limits of the test, the following QC procedures mustbe followed when analyzing sodium.14.2 Calibration and Calibration Verification:14.2.1 Analyze at least four working standards containingconcentration
34、s of sodium that bracket the expected sampleconcentration, prior to analysis of samples, to calibrate theinstrument. The calibration correlation coefficient shall beequal to or greater than 0.990. In addition to the initialcalibration blank, a calibration blank shall be analyzed at theend of the bat
35、ch run to ensure contamination was not a problemduring the batch analysis.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 known concen
36、tration.14.2.3 If calibration cannot be verified, recalibrate theinstrument.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, etc., a pre
37、cision 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 the solution
38、 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. This study sh
39、ould be repeated until the recoveries arewithin the limits given in Table 1. If a concentration other thanthe recommended concentration is used, refer to PracticeD 5847 for information on applying the F test and t test inevaluating the acceptability of the mean and standard devia-tion.14.4 Laborator
40、y 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 or 10 samples. If large numbers of samples are analyzedin the batch, analyze the LCS after every 10 samples. Thelaboratory control samples for a large ba
41、tch should cover theanalytical range when possible. The LCS must be takenthrough all of the steps of the analytical method includingsample preservation and pretreatment. The result obtained fora mid-range LCS shall fall within 615 % of the knownconcentration.14.4.2 If the result is not within these
42、limits, analysis ofsamples is halted until the problem is corrected, 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
43、test blank with each batch.The concentration of sodium found in the blank should be lessthan 0.5 times the lowest calibration standard. If the concen-tration of sodium is found above this level, analysis of samplesis halted until the contamination is eliminated, and a blankshows no contamination at
44、or above this level, or the resultsmust be qualified with an indication that they do not fall withinthe performance criteria of the test method.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 eachbatch by spiking a
45、n aliquot of the sample with a knownconcentration of sodium and taking it through the analyticalmethod.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
46、 times the analyte concentration 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 5 100 AVs1 V! 2 BVs# / CV (1)where:A = analyte concentration (mg/L) in spiked samp
47、le,B = analyte concentration (mg/L) in unspiked sample,C = concentration (mg/L) of analyte in spiking solution,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 concentration, listed
48、 in GuideD 5810, Table 1. If the percent recovery is not within theselimits, a matrix interference may be present in the sampleselected for spiking. Under these circumstances, one of thefollowing remedies must be employed: the matrix interferencemust be removed, all samples in the batch must be anal
49、yzed bya test method not affected by the matrix interference, or theresults must be qualified with an indication that they do not fallwithin the performance criteria of the test method.NOTE 4Acceptable spike recoveries are dependent on the concentra-tion of the component of interest. See Guide D 5810 for additionalinformation.14.7 Duplicate:14.7.1 To check the precision of sample analyses, analyze asample in duplicate with each batch. If the concentration of theanalyte is less than five times the detection limit for the analyte,a matrix spike duplicate (MSD) shoul
