1、Designation: D4658 15Standard Test Method forSulfide Ion in Water1This standard is issued under the fixed designation D4658; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicat
2、es the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method uses an ion-selective electrode todetermine sulfide ion in water. The test method is applicable inthe range from 0.04 to 4000 mg/L of sulfide.1.2
3、Precision data presented in this test method were ob-tained using reagent water only. It is the users responsibility toensure the validity of this test method for untested types ofwater.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thi
4、sstandard.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 determine the applica-bility of regulatory limitations prior to use. Sulf
5、ide samples,when acidified, can release highly toxic hydrogen sulfide gas.For a specific precautionary statement, see 7.5.2. Referenced Documents2.1 ASTM Standards:2D1129 Terminology Relating to WaterD1193 Specification for Reagent WaterD2777 Practice for Determination of Precision and Bias ofApplic
6、able Test Methods of Committee D19 on WaterD3370 Practices for Sampling Water from Closed ConduitsD4127 Terminology Used with Ion-Selective ElectrodesD5810 Guide for Spiking into Aqueous SamplesD5847 Practice for Writing Quality Control Specificationsfor Standard Test Methods for Water Analysis3. Te
7、rminology3.1 Definitions:3.1.1 For definitions of terms used in this test method, referto Terminology D1129.3.2 Definitions of Terms Specific to This Standard:3.2.1 For definitions of terms specific to this test method,refer to Terminology D4127.4. Summary of Test Method4.1 Sulfide ion is measured p
8、otentiometrically using asulfide ion-selective electrode in conjunction with a double-junction sleeve type reference electrode. Potentials are readusing a pH meter having an expanded millivolt scale capable ofbeing read to the nearest 0.1 mV, or a specific ion meter havinga direct concentration scal
9、e for sulfide ion.4.2 Samples are treated prior to analysis with sulfide anti-oxidant buffer (SAOB). This buffer fixes the solution pH at ahighly alkaline level and contains ascorbic acid to retard airoxidation of sulfide ion in solution.This ensures that the sulfidepresent occurs chiefly as S2ion r
10、ather than as complexed HS1or H2S that are present at lower pH values.5. Significance and Use5.1 Sulfide ion is found in ground waters and wastewater,causing odor and corrosion problems. If acidified, these waterscan release hydrogen sulfide, which is extremely toxic even atlow levels. This test met
11、hod provides a means for interference-free measurement of free sulfide ion.NOTE 1Sulfide forms complexes with hydrogen ions (HS1and H2S).In addition, sulfide ion forms soluble complexes with elemental sulfur(S22,S32,S42, etc.), tin, antimony, and arsenic ions.6. Apparatus6.1 pH Meter, with expanded
12、millivolt scale, or a specificion meter having a direct concentration scale for sulfide ion.6.2 Sulfide Ion-Selective Electrode.6.3 Reference Electrode, double-junction sleeve type with1.0 M potassium nitrate solution, pH adjusted to 13.5 with 1.0M sodium hydroxide in the outer sleeve.1This test met
13、hod is under the jurisdiction of ASTM Committee D19 on Waterand are the direct responsibility of Subcommittee D19.05 on Inorganic Constituentsin Water.Current edition approved March 15, 2015. Published April 2015. Originallyapproved in 1987. Last previous edition approved in 2009 as D4658 09. DOI:10
14、.1520/D4658-15.2For 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 e
15、nd of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States17. Reagents7.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the sp
16、ecifications of the Commit-tee onAnalytical Reagents of theAmerican Chemical Society.3Other grades may be used, provided it is first ascertained thatthe reagent is of sufficiently high purity to permit its usewithout lessening the accuracy of the determination.7.2 Purity of WaterUnless otherwise ind
17、icated, referenceto water shall be understood to mean reagent water conformingto Specification 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
18、test method. Type IIIwater was specified at the time of round robin testing of thismethod.7.3 Cadmium Nitrate Solution (0.1 M)Place 12.84 g ofcadmium oxide into a 125-mL beaker. Add 12 to 14 mL ofconcentrated nitric acid (sp gr 1.42), stir with a glass stirringrod, and add about 10 mL of water. Stir
19、 thoroughly, add anadditional 40 to 50 mL of water, washing off the glass stirringrod with part of the water. Transfer to a 1-L volumetric flaskand dilute to 1000 mL with water.7.4 Lead Perchlorate Solution (0.1 M)Commerciallyavailable. Alternatively, it can be prepared using lead perchlo-rate and w
20、ater. Dissolve 46.02 g of the salt in water using a 1-Lvolumetric flask and dilute to 1000 mL with water.7.5 Sodium Sulfide Solution, StockPrepare sodium sulfidestock solution from sodium sulfide hydrate (Na2S9H2O).Alternatively, certified sodium sulfide stock solutions of knownpurity are commercial
21、ly available through chemical supplyvendors and may be used. (WarningAll sulfide solutionpreparation and measurement must be performed in a hood toavoid breathing noxious fumes.)7.5.1 Precise standards cannot be prepared by weighing thesalt because of the large and variable water of hydration.Instea
22、d, prepare a saturated sodium sulfide solution by addingapproximately 100 g of the Na2S9H2O to approximately 100mLof water, shake well, stopper securely, and allow it to stand,at least overnight.7.5.2 To prepare the sodium sulfide stock solution, pipette 1mL of the saturated solution described above
23、 into 50 mL ofSAOB (7.6), and dilute to 100 mL with water.7.6 Sulfide Anti-Oxidant Buffer (SAOB)In a 1000-mLbeaker containing approximately 600 mLof water, add 200 mLof 10 M sodium hydroxide (or 80 g pellets), 35 g of ascorbicacid, and 67 g of disodium EDTA. Stir until everythingdissolves and transf
24、er the solution to a 1000-mL volumetricflask. Dilute to the mark with water. The solution compositionis as follows; 2 M NaOH; 0.2 M ascorbic acid, and 0.2 Mdisodium EDTA (dihydrate).NOTE 2Freshly prepared SAOB, when stored in a tightly stopperedbottle, has a shelf life of approximately two weeks, if
25、 opened frequently.When oxidized, the solution turns dark brown and should be discarded.7.7 Zinc Acetate Solution (2.0 M)Dissolve 43.90 g of zincacetate Zn(C2H3O2)22H2O in water, using a 100 mL volu-metric flask, and dilute to 100 mL with water.8. Sampling and Storage8.1 Collect samples in accordanc
26、e with Practices D3370.8.2 Samples should be taken with a minimum of aeration toavoid air oxidation of sulfide or loss of volatile hydrogensulfide from the sample. Preserve samples by adding 0.2 mL (4drops) of 2 M zinc acetate (equivalent to 128 mg/L S=2) and0.05 mL (1 drop) of 6 M sodium hydroxide
27、to a 100-mL bottle.Fill the bottle completely with the sample and stopper it. Thereshould be no air bubbles trapped under the stopper. If theconcentration of sulfide is greater than approximately 100mg/L, the amounts of both reagents should be increased.8.3 Sulfide in samples that have been “preserv
28、ed” with zincacetate can be determined without special treatment, sinceSAOB contains EDTA to redissolve the zinc and free thesulfide. The entire sample is used for analysis, and since theresults will be given in milligrams sulfide per litre, the samplevolume must be known.8.4 The standards must be t
29、reated the same as the samples.9. Calibration9.1 Prepare four calibration standards each day using100-mL volumetric flasks as follows:9.1.1 Standard A5.00 mL of sodium sulfide stocksolution, 50 mLof SAOB (use a graduated cylinder), and diluteto a total volume of 100 mL with water.9.1.2 Standard B1.0
30、0 mL of sodium sulfide stocksolution, 50 mLof SAOB (use a graduated cylinder), and diluteto a total volume of 100 mL with water.9.1.3 Standard C2.00 mL of calibration standard A,50mL of SAOB (use a graduated cylinder), and dilute to a totalvolume of 100 mL with water.9.1.4 Standard D1.00 mL of calib
31、ration standard A,50mL of SAOB (use a graduated cylinder), and dilute to a totalvolume of 100 mL with water.9.2 The concentrations of the calibration standards, inmilligrams per litre, are based on a 50 mL standard volumediluted 1:1 with SAOB and are calculated from theconcentration, S, of the sodiu
32、m sulfide stock solution asdetermined by titration:A = 0.1SB = 0.02SC = 0.002SD = 0.001S9.3 Prepare a calibration curve by immersing the electrodepair in each of the calibration standards, beginning with themost dilute, and record the stable electrode potential millivoltreading developed in each. Co
33、nstruct a graph using this data,3Reagent Chemicals, American Chemical 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.,
34、and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.D4658 152using semilog paper. Record the sulfide ion concentrations onthe logarithmic scale and the millivolt readings on the linearscale (Fig. 1). A specific ion meter having a direct
35、concentra-tion scale for sulfide ion may be used.10. Standardization10.1 The concentration of the sodium sulfide stock solutionmust be determined by potentiometric titration before proceed-ing with the calibration.10.2 Take 50 mL of sodium sulfide stock solution, and addto it 25 mL of SAOB and 25 mL
36、 of water. Titrate using thesulfide and double-junction reference electrodes as the end-point indicator, and either the lead perchlorate or cadmiumnitrate solution as the titrant.10.3 Calculate the concentration (S) of sodium sulfide stocksolution in mg/L as follows:S 5 mL of0.1 M lead perchlorate o
37、r cadmium nitrate! 364.12 (1)where:64.12 = (0.1 mole/L titrant 32.06 g/mole S 1000 mg/g)/ 50 mL sulfide stock.11. Procedure11.1 Pipette a sample into an equal volume of SAOB, stirthoroughly without vortex, and allow it to stand for 3 to 5 min.Place the electrodes in the solution, record the stable e
38、lectrodepotential, and determine the sulfide ion concentration of thesample from the calibration curve.11.2 Between samples, rinse the electrodes with water, blotdry, and immerse in a “blank” solution of 50 mLSAOB plus 50mL water.11.3 To measure the next sample, blot the electrodes dry andrepeat 11.
39、1.12. Precision and Bias412.1 The instability of sulfide ion in the presence of oxygenmakes conventional round robin testing (the distribution of“unknowns” to a number of laboratories) an impossibility. Forthat reason, and with the concurrence and advice of the ResultsAdvisor, this test method was t
40、ested as described here, so thatusers of this test method might have some guidance as to thevalidity of their results.12.2 On each of three days, operators in each of sixlaboratories standardized a sodium sulfide stock solution asdescribed in Section 10. Full calibration, using four standardsprepare
41、d by dilution of the standardized stock solution, wascarried out five times on each day by each operator, and thepotential values were recorded.12.3 The five replicates at each level were averaged andstandard deviations were calculated. By averaging the standarddeviation values in segments of the co
42、ncentration range, Table1 was developed. Since the sodium sulfide stock solutionsvaried from day to day, this approach was chosen to providethe most useful information. The data show the averagestandard deviation in millivolts (from which concentrationvariations may be calculated) that an average us
43、er may expectat the concentrations indicated.12.4 An additional, rather unusual, treatment of the data isshown in Fig. 2. Each of the nominal concentration values isplotted against the average of five potential values obtained forit (72 points), as if all had been obtained by one laboratory.Letters
44、are used to indicate which data came from whichlaboratory. The straight line combines data taken by sixdifferent operators using six different electrode pairs on threedifferent days at 72 different concentrations, with all laborato-ries using the same procedure. It is intended only to provide apoten
45、tial user of this test method with a practical, if notcompletely statistically valid, estimate of the kinds of resultswhich can be expected.12.5 The testing described was carried out using reagentwater only. It is the users responsibility to ensure the validityof this test method for untested types
46、of water.12.6 This precision statement has been reviewed and ap-proved by the Results Advisor, with the concurrence of theTechnical Operations Section of Executive SubcommitteeD19.90 at their meeting on November 5, 1985 for conformanceto Section 1.4 of Practice D2777 13.13. Quality Control13.1 In or
47、der to be certain that analytical values obtainedusing these test methods are valid and accurate within theconfidence limits of the test, the following QC procedures mustbe followed when analyzing sulfide ion.13.2 Calibration and Calibration Verification:13.2.1 Analyze at least three working standar
48、ds containingconcentrations of sulfide ion that bracket the expected sampleconcentration, prior to analysis of samples, to calibrate theinstrument. The calibration correlation coefficient shall beequal to or greater than 0.990.13.2.2 Verify instrument calibration after standardization byanalyzing a
49、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.13.2.3 If calibration cannot be verified, recalibrate theinstrument.4Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D19-1127. ContactASTM CustomerService at serviceastm.org.FIG. 1 Typical Electrode Response to Sulfide IonD4658 15313.2.4 It is recommended to analyze a blank and continuingcalibration verification (CCV)
