1、Designation: D 4191 03Standard 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 (e) 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
3、this 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 f
4、or 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 insuff
5、icient 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 This standard does not purport to ad
6、dress 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.2. Referenced Documents2.1 ASTM Standards:D 1066 Practi
7、ce for Sampling Steam3D 1129 Terminology Relating to Water3D 1192 Specification for Equipment for Sampling Waterand Steam in Closed Conduits3D 1193 Specification for Reagent Water3D 2777 Practice for Determination of Precision and Bias ofApplicable Methods of Committee D-19 on Water3D 3370 Practice
8、for Sampling Water from Closed Conduits3D 3561 Test Method for Lithium, Potassium, and SodiumIons in Brackish Water, Seawater, and Brines by AtomicAbsorption Spectrophotometry4D 5810 Guide for Spiking into Aqueous Samples3D 5847 Practice for the Writing Quality Control Specifica-tions for Standard T
9、est Methods for Water Analysis33. 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 by aspiratingthe low solids samp
10、le 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 particularly significant in potable wate
11、rexcept 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 contain significant quantitiesof s
12、odium. 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 manufacturers instructions should be fol
13、lowed 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 method is under the jurisdiction o
14、f ASTM Committee D19 on Waterand is the direct responsibility of Subcommittee D19.05 on Inorganic Constituentsin Water.Current edition approved Jan. 10, 2003. Published January 2003. Originallyapproved in 1982. Last previous edition approved in 1997 as D 4191 97.2Platte, J. A., and Marcy, V. M., “A
15、New Tool for the Water Chemist,” IndustrialWater Engineering, May 1965.3Annual Book of ASTM Standards, Vol 11.01.4Annual Book of ASTM Standards, Vol 11.02.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshoh
16、ocken, PA 19428-2959, United States.7.3 Oxidant: Air, which has been passed through a suitablefilter to remove oil, water, and other foreign substances is theusual oxidant.7.4 Fuel: AcetyleneStandard, commercially availableacetylene is the usual fuel. Acetone, always present in acety-lene cylinders
17、can affect analytical results. The cylinder shouldbe replaced at 50 psig (345 kPa) to avoid acetone carryover.7.4.1 Caution“Purified” grade acetylene containing aspecial proprietary solvent rather than acetone should not beused with poly(vinyl chloride) tubing as weakening of thetubing walls can cau
18、se a potentially hazardous situation.7.5 Pressure-Reducing ValvesThe supplies of fuel andoxidant shall be maintained 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. U
19、nless 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.5Other grades may beused, provided it is first ascertained that the reagent is ofsufficientl
20、y 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 Specification D 1193, Type I. Other reagent water types maybe used provided it is first ascertain
21、ed 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 method.8.3 Sodium Solution, Stock (1.0 mL = 1.0 mg Na)Drysodium chloride to constant weigh
22、t at 105C. Dissolve 2.5418g of the dry sodium chloride (NaCl) in water and dilute to 1 Lwith 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
23、water.9. Sampling9.1 Collect the samples in accordance with the applicableASTM test method as follows: Practices D 3370, PracticeD 1066, and Specification D 1192.10. Standardization10.1 Prepare 100 mL each of a blank and at least fourstandard solutions to bracket the expected sodium concentra-tion r
24、ange 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. Select the standardsto give zero, middle, and maximum points for an analyticalcurve.10.2 Aspirate the blank and the standards and record theinstr
25、ument readings. Aspirate water between standards.10.3 Prepare an analytical curve by plotting the absorbanceversus 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 sam
26、ple 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 to a prepared analytical curve (10.3)or reading directly in co
27、ncentration if the capability is providedwith the instrument.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 Bias613.1 The overall and single-operator precision of this testmethod for
28、 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 test method is de
29、signated 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 1.13.3 Precision and bias for this test method conforms toPrac
30、tice D 2777 77, which was in place at the time ofcollaborative testing. Under the allowances made in 1.4 ofPractice D 2777 98, 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 analy
31、tical values obtainedusing these test methods are valid and accurate within the5“Reagent Chemical, American Chemical Society Specifications,” Am. Chemi-cal Soc., Washington, DC. For suggestions on the testing of reagents not listed bythe American Chemical Society, see “Analar Standards for Laborator
32、y Chemicals,”BDH Ltd., Poole, Dorset, U.K., and the “United States Pharmacopeia.”6Supporting data are available from ASTM Headquarters. Request RR: D19-1080.TABLE 1 Determination of Bias for Sodium in Reagent Water byAtomic AbsorptionAmountAdded,mg/LAmountFound,mg/LStSoBias %0.20 0.184 0.053 0.024 8
33、.01.20 1.25 0.094 0.028 + 4.172.70 2.81 0.129 0.081 + 4.07D4191032confidence 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 three working standards containingconcentrations of sodium that bra
34、cket 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 batch run to ensure con
35、tamination 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 concentration.14.2.3 If ca
36、libration 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 precision andbias study
37、 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 used in thecollabor
38、ative study. Each replicate must be taken through thecomplete analytical test method including any sample preser-vation and pretreatment steps. The replicates may be inter-spersed with samples.14.3.3 Calculate the mean and standard deviation of theseven values and compare to the acceptable ranges of
39、 bias inTable 1. This 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 PracticeD 5847 for information on applying the F test and t test inevaluating the acceptability of the mean and stan
40、dard devia-tion.14.4 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 or 10 samples. If large numbers of samples are analyzedin the batch, analyze the LCS after every 10 samples. Thelaboratory
41、control samples for a large batch 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 t
42、he result is not within these 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:1
43、4.5.1 Analyze a reagent water 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 b
44、lankshows no contamination at 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 samp
45、le from eachbatch by spiking an 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 t
46、he spikedsample that is 2 to 5 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 conce
47、ntration (mg/L) in spiked sample,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) added with spike.14.6.4 The percent recovery of the spike shall fall within thelimits, based on the analyte
48、concentration, listed 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 t
49、he batch must be analyzed 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
