ASTM D4658-2008 Standard Test Method for Sulfide Ion in Water.pdf

1、Designation: D 4658 08Standard Test Method forSulfide Ion in Water1This standard is issued under the fixed designation D 4658; 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 indic

2、ates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 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 th

4、isstandard.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. Sul

5、fide samples,when acidified, can release highly toxic hydrogen sulfide gas.For a specific precautionary statement, see Note 2.2. Referenced Documents2.1 ASTM Standards:2D 1129 Terminology Relating to WaterD 1193 Specification for Reagent WaterD 2777 Practice for Determination of Precision and Bias o

6、fApplicable Test Methods of Committee D19 on WaterD 3370 Practices for Sampling Water from Closed ConduitsD 4127 Terminology Used with Ion-Selective ElectrodesD 5810 Guide for Spiking into Aqueous SamplesD 5847 Practice for Writing Quality Control Specificationsfor Standard Test Methods for Water An

7、alysis3. Terminology3.1 Definitions: For definitions of terms used in this testmethod, refer to Terminology D 1129.3.2 Definitions of Terms Specific to This Standard:3.2.1 For definitions of terms specific to this test method,refer to Terminology D 4127.4. Summary of Test Method4.1 Sulfide ion is me

8、asured potentiometrically 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 concentrat

9、ion scale 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

10、 S2ion rather than as complexedHS1or 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 t

11、est method 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 ex

12、panded millivolt scale, or a specificion meter having a direct concentration scale for sulfide ion.6.2 Sulfide Ion-Selective Electrode.1This test method is under the jurisdiction of ASTM Committee D19 on Waterand are the direct responsibility of Subcommittee D19.05 on Inorganic Constituentsin Water.

13、Current edition approved Aug. 15, 2008. Published August 2008. Originallyapproved in 1987. Last previous edition approved in 2003 as D 4658 03.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards vo

14、lume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6.3 Reference Electrode, double-junction sleeve type with1.0 M potassium nitrate solution, pH adjusted

15、to 13.5 with 1.0M sodium hydroxide in the outer sleeve.7. Reagents7.1 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 onAnalytical Reagents of theAmerican Chemical S

16、ociety.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 indicated, referenceto water shall be understood to mean reagent water conforming

17、to 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 of the test method. Type IIIwater was specified at the time of round robin testing o

18、f 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 thoroughly, add anadditional 40 to 50 mL of water, washing off the glass sti

19、rringrod 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 water. Dissolve 46.02 g of the salt in water using a 1-Lvolumetric flask and d

20、ilute to 1000 mL with water.7.5 Sodium Sulfide Solution, StockPrepare sodium sulfidestock solution from sodium sulfide hydrate (Na29H2O).NOTE 2Warning: All sulfide solution preparation and measurementmust be performed in a hood to avoid breathing noxious fumes.7.5.1 Precise standards cannot be prepa

21、red by weighing thesalt because of the large and variable water of hydration.Instead, 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 s

22、odium sulfide stock solution, pipette 1mL of the saturated solution described above 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

23、 ascorbicacid, and 67 g of disodium EDTA. Stir until everythingdissolves and transfer 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 3Freshly prepared SAOB, when s

24、tored in a tightly stopperedbottle, has a shelf life of approximately two weeks, if 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 ofzinc acetate Zn(C2H3O2)22H2O in water, using a 100 mLvolumetric flask, and di

25、lute to 100 mL with water.8. Sampling and Storage8.1 Collect samples in accordance with Practices D 3370.8.2 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

26、 acetate (equivalent to 128 mg/L S=2) and0.05 mL (1 drop) of 6 M sodium hydroxide 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 o

27、f both reagents should be increased.8.3 Sulfide in samples that have been “preserved” 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 millig

28、rams sulfide per litre, the samplevolume must be known.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 stock solu-tion, 45 mL of SAOB (use a graduated cylinder), and dilute to100 mL with water.9.1.2 Stan

29、dard B1.00 mL of sodium sulfide stock solu-tion, 50 mL of SAOB (use a graduated cylinder), and dilute to100 mL with water.9.1.3 Standard C2.00 mL of calibration standard A,50mL of SAOB (use a graduated cylinder), and dilute to 100 mLwith water.9.1.4 Standard D1.00 mL of calibration standard A,50mL o

30、f SAOB (use a graduated cylinder), and dilute to 100 mLwith water.9.2 The concentrations of the calibration standards, inmilligrams per litre, are calculated from the concentration, S,ofthe sodium sulfide stock solution as determined by titration:A = 0.05SB = 0.01SC = 0.001SD = 0.0005S9.3 Prepare a

31、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. Construct a graph using this data,using semilog paper. Record the sulfide ion concentrations onthe logar

32、ithmic scale and the millivolt readings on the linearscale (Fig. 1).10. Standardization10.1 The concentration of the sodium sulfide stock solutionmust be determined by potentiometric titration before proceed-ing with the calibration.3Reagent Chemicals, American Chemical Society Specifications, Ameri

33、canChemical 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, Inc. (USPC

34、), Rockville,MD.D465808210.2 Take 50 mL of sodium sulfide stock solution, and addto it 25 mL of SAOB and 25 mL 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 Calcul

35、ate the concentration (S) of sodium sulfide stocksolution in mg/L as follows:S 5 mL of 0.1 M lead perchlorate or cadmium nitrate!364.1211. 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 solu

36、tion, record the stable electrodepotential, 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 ele

37、ctrodes dry andrepeat 11.1.12. 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 ResultsAdviso

38、r, this test method was tested 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, us

39、ing four standardsprepared 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 val

40、ues in segments of the concentration 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 calcu

41、lated) that an average user 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 b

42、y one laboratory.Letters 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 intend

43、ed only to provide apotential 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 m

44、ethod for untested types 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 D 2777 06.13.

45、 Quality Control13.1 In order 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 l

46、east three working standards 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. In addition to the initialcalibration blank, a

47、 calibration blank shall be analyzed at theend of the batch run to ensure contamination was not a problemduring the batch analysis.13.2.2 Verify instrument calibration after standardization byanalyzing a standard at the concentration of one of thecalibration standards. The concentration of a mid-ran

48、ge stan-dard should fall within 615 % of the known concentration.13.2.3 If calibration cannot be verified, recalibrate theinstrument.13.3 Initial Demonstration of Laboratory Capability:13.3.1 If a laboratory has not performed the test before, or ifthere has been a major change in the measurement sys

49、tem, forexample, new analyst, new instrument, etc., a precision andbias study must be performed to demonstrate laboratorycapability.13.3.2 Analyze seven replicates of a standard solutionprepared from an Independent Reference Material containing amid-range concentration of sulfide ion. The matrix and chem-istry of the solution should be equivalent to the solution usedin the collaborative study. Each replicate must be taken throughthe complete analytical test method including any samplepreservation and pretreatment steps. The replicates may beinterspersed