1、Designation: D 4193 08Standard Test Method forThiocyanate in Water1This standard is issued under the fixed designation D 4193; 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. Scope*1.1 This test method covers the quantitative colorimetriclaboratory measurement of dissolved thiocyanate in water,waste water, and saline water in the range from 0.1
3、 to 2.0 mg/L.For higher concentrations, use an aliquot from the dilutedsample.1.1.1 ValidationThis test method was validated over therange of 0.07 to 1.42 mg/L. This test method was validated atnine laboratories at four levels. This test method may be validfor reporting results down to lower levels
4、as validated inindividual user laboratories.1.1.2 ApplicationThis test method has been validated inreagent water, Type II, in multiple laboratories and 7 naturalwaters, 1 laboratory effluent, 1 steel mill effluent, and 2dechlorinated and treated sanitary effluents in single laborato-ries. It is the
5、users responsibility to assure the validity of thetest method on any untested matrices.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns, if any, associat
6、ed 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. For specific hazardstatements, see Section 9.2. Referenced Documents2.1 ASTM Standards:2D 1129 Terminol
7、ogy Relating to WaterD 1192 Guide for Equipment for Sampling Water andSteam in Closed Conduits3D 1193 Specification for Reagent WaterD 2036 Test Methods for Cyanides in WaterD 2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD 3370 Practices fo
8、r Sampling Water from Closed ConduitsD 3856 Guide for Good Laboratory Practices in Laborato-ries Engaged in Sampling and Analysis of WaterD 4210 Practice for Intralaboratory Quality Control Proce-dures and a Discussion on Reporting Low-Level Data3D 4841 Practice for Estimation of Holding Time for Wa
9、terSamples Containing Organic and Inorganic ConstituentsD 5788 Guide for Spiking Organics into Aqueous SamplesD 5789 Practice for Writing Quality Control Specificationsfor Standard Test Methods for Organic Constituents3D 5847 Practice for Writing Quality Control Specificationsfor Standard Test Metho
10、ds for Water AnalysisD 7237 Test Method for Aquatic Free Cyanide with FlowInjection Analysis (FIA) Utilizing Gas Diffusion Separa-tion and Amperometric DetectionD 7365 Practice for Sampling, Preservation and MitigatingInterferences in Water Samples for Analysis of CyanideE60 Practice for Analysis of
11、 Metals, Ores, and RelatedMaterials by Molecular Absorption SpectrometryE 275 Practice for Describing and Measuring Performanceof Ultraviolet, Visible, and Near-Infrared Spectrophotom-eters3. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod, refer to Terminology D 1129.4. S
12、ummary of Test Method4.1 This test method consists of thiocyanate reacting withferric ions at a pH of2toform a colored complex which isdetermined colorimetrically at 460 nm and adheres to BeersLaw.4.2 Industrial wastes may be highly colored and containvarious interfering organic compounds which must
13、 be removedby adsorption on macroreticular resin4prior to analysis.5. Significance and Use5.1 This test method is useful for analysis of many naturalwaters that contain thiocyanate from organic decomposition1This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct r
14、esponsibility of Subcommittee D19.06 on Methods forAnalysis forOrganic Substances in Water.Current edition approved May 1, 2008. Published June 2008. Originallyapproved in 1982. Last previous edition approved in 2002 as D 4193 02.2For referenced ASTM standards, visit the ASTM website, www.astm.org,
15、orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn.4Spencer, R. R., Leenheer, J., and Marti, V. C., “Automated ColorimetricDetermination of Thiocyanate, Thiosulfate, and T
16、etrathionate in Water, AOAC94th Annual Meeting, Washington, DC, 1980.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.products and waste water discharges. Some industri
17、al wastes,such as those from the metallurgical processing of gold ores,steel industry, petroleum refining, and coal gasification, maycontain significant concentrations of thiocyanate. Thiocyanateper se is not recognized as a toxic chemical compound.However, when chlorinated, thiocyanate is converted
18、 to thehighly toxic and volatile cyanogen chloride at high pH.Oxidation of thiocyanate may also release toxic hydrogencyanide. The user of the method is advised to perform holdingtime studies in accordance with Practice D 4841 wheneveroxidants are present in the samples.5.1.1 For information on the
19、impact of cyanogens andcyanide compounds, seeAppendix X1 of Test Method D 2036.6. Interferences6.1 Hexavalent chromium interference is removed by ad-justing the pH to 2 with concentrated nitric acid and addingferrous sulfate. Raising the pH to 8.5-9 with sodium hydroxideprecipitates Fe (III) and Cr
20、(III) as the hydroxides, which areremoved by filtration.6.2 Reducing agents that reduce Fe (III) to Fe (II), thuspreventing formation of the ferric thiocyanate complex, aredestroyed by a few drops of hydrogen peroxide.6.3 High concentrations of cyanide in proportion to theconcentration of thiocyanat
21、e will react with the iron to formcolored complexes.6.4 Colored or interfering organic compounds must beremoved by adsorption on macroreticular adsorption resin priorto analysis.NOTE 1Examples of interfering compounds are fluoride, phosphate,oxalate, arsenate, tartrate, borate, etc. which form compl
22、exes with iron.5Production of a red color with ferric ions is typical of phenols, enols,oximes, and acetates.66.5 Oxidation of thiocyanate may also react to form cya-nides, resulting in low results. The user of the method isadvised to perform holding time studies in accordance withPractice D 4841 wh
23、enever oxidants are present in the samples.6.6 Removal of sulfides for cyanide analysis preservationmay result in reaction of cyanide to form thiocyanate. Use aseparate sample for thiocyanate analysis than the one preservedfor cyanide analysis.7. Apparatus7.1 Spectrophotometer or Filter Photometer,
24、suitable forabsorbance measurements at 460 nm and using a 5-cm cell.Filter photometers and photometric practices used in this testmethod shall conform to Practice E60. Spectrophotometersshall conform to Practice E 275.7.2 ColumnChromatographic, glass, 12-mm inside diam-eter by 600-mm length, equippe
25、d with a reservoir and stop-cock, or a 50-mL buret with a glass wool plug and a funnelattached with a short piece of tubing.8. Reagents and Materials8.1 Purity of ReagentsReagent-grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to t
26、he specifications of the Commit-tee onAnalytical Reagents of theAmerican Chemical Society.78.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent water conformingto Specification D 1193, Type I or II, and demonstrated to befree of specific interference
27、for the test being performed.8.3 Acetone.8.4 Ferric Nitrate Solution (404 g/L)Dissolve 404 g offerric nitrate (Fe(NO3)39H2O) in about 800 mL of water.Addto this solution 80 mL of concentrated nitric acid. Mix anddilute to 1 L with water.8.5 Hexane.8.6 Hydrogen Peroxide Solution(H2O2), 30 %.8.7 Macro
28、reticular Resin8, 18- to 50-mesh or equivalent.8.8 Methyl Alcohol.8.9 Nitric AcidConcentrated HNO3, sp gr 1.42.8.10 Nitric Acid (0.1 M)Mix 6.4 mLof concentrated nitricacid in about 800 mL of water. Dilute to 1 L with water andmix.8.11 Thiocyanate Solution, Stock (1 mL = 1.0 mg SCN)Dissolve 1.673 g o
29、f potassium thiocyanate (KSCN) in waterand dilute to 1 L.8.12 Thiocyanate Solution, Standard (1 mL = 0.01 mgSCN1)Dilute 10 mL of the stock thiocyanate solution to 1L with water. Prepare fresh for each use. See 10.4.8.13 Sodium Hydroxide Solution (4 g/L)Dissolve4gofNaOH in about 800 mL of water. Mix
30、and dilute to 1 L withwater.9. Precautions9.1 Many samples will also contain cyanide. Because of thetoxicity of cyanide, great care must be exercised in itshandling. Acidification of cyanide solutions produces toxichydrocyanic acid (HCN). All manipulations must be done inthe hood so that any HCN gas
31、 that might escape is safelyvented.9.2 Residual sample remains could be toxic; these should bedisposed of properly.10. Sampling10.1 Collect the sample in accordance with SpecificationD 1192 and Practices D 3370.10.2 Thiocyanate is stable in both the acid and alkaline pHrange.10.3 If the sample is to
32、 be preserved for cyanide, remove thesulfide before stabilization at a high pH in accordance with5Newman, A. A. (ed.), Chemistry and Biochemistry of Thiocyanic Acid and ItsDerivatives, Academic Press, New York, NY, 1975.6Shriner, R. L., and Fuson, R. C., Identification of Organic Compounds, JohnWile
33、y however, be careful not to over dilute the sample asthe detection limit will be elevated by this factor. In theaforementioned example, the dilution factor would be equal to5 (total volume/sample volume). Clearly indicate the dilutionvolumes on the sample and chain-of-custody form so that thelabora
34、tory can mathematically correct the result.10.3.1.2 Alternatively, sulfide can be removed by precipita-tion if free cyanide is the only form of cyanide to be measured(Test Method D 7237). For removal of sulfide by precipitation,if the pH is less than pH 11, raise the pH to 11 with NaOHsolution, and
35、then add approximately 1 mg of powderedcadmium chloride for each ml of sample. Cap and shake thecontainer to mix. Allow the precipitate to settle and test thesample with lead acetate paper for residual sulfide. If neces-sary, add more cadmium chloride but avoid adding excess.Finally filter through a
36、 0.45 m filter. Refrigerate, then trans-port or ship the filtrate to the laboratory.NOTE 2Some analytical methods prescribe the use of lead carbonateor lead acetate to precipitate sulfide; however, sulfide and cyanide canform thiocyanate in the presence of lead causing decreased cyaniderecoveries; t
37、herefore, lead carbonate and lead acetate should be avoided.Methods that specify the addition of bismuth nitrate to treat sulfide duringtotal cyanide distillations have been demonstrated by ASTM committeeD19.06 to be ineffective. Caution: Cyanide can be converted intothiocyanate in the presence of s
38、ulfide at a high pH, causing high results.10.4 Thiocyanate is biodegradable. Samples that may con-tain bacteria should be preserved at pH 2 by the addition ofmineral acid and refrigerated.11. Preparation of Apparatus11.1 Resin ColumnMeasure out sufficient resin to fill thecolumn or columns into a be
39、aker and add five times the resinvolume of acetone. Stir for 1 h with gentle agitation.11.2 Pour off the fines and the acetone from the settled resinand add five times the resin volume of hexane. Stir for 1 h.11.3 Pour off any fines that may be present and the hexanefrom the settled resin and add fi
40、ve times the resin volume ofmethanol. Stir for 15 min.11.4 Pour off the methanol from the settled resin and addthree times the resin volume of NaOH solution (4 g/L). Stir for15 min.11.5 Pour off the NaOH solution from the settled resin andadd three times the resin volume of 0.1 M HNO3. Stir for 15mi
41、n.11.6 Pour off the HNO3solution from the settled resin andadd three times the resin volume of reagent water. Stir for 15min. Decant the water from the settled resin and use thispurified resin to fill the column.11.7 Attach the tip of the column to a source of reagentwater, and displace the air from
42、 the column with water to thebottom of the reservoir (tip of the funnel if a buret is used).11.8 Add the resin slurry to the reservoir (funnel) and allowit to fill the column by displacing the water to approximately400-mm depth. This procedure will give a uniform columnwith the correct degree of pac
43、king.11.9 When the resin has settled allow the water to drain tothe top of the resin bed. At no time should the liquid level bebelow the top of the resin bed.11.10 Add and drain five 5-mL increments of samplesolution to the column. Fill the reservoir (funnel) with theremaining (125 mL) solution and
44、allow it to pass through thecolumn at a rate of 20 mL/min. Discard the first 50 mL ofeluate.11.11 Collect the next 50 mL of eluate in a clean, dry,graduated cylinder. Use this portion for color development.11.12 Drain any remaining solution to the top of the resinbed. Regenerate the resin by the ser
45、ial addition of five 5-mLand one 75-mL portions of NaOH solution (4 g/L), five 5-mLand one 25-mLportions of 0.1 M HNO3and five 5-mLand one75-mL portions of water. If the flow rate has reduced to 4 to 5mL/min, it is advisable to rinse the resin with 100 mL ofmethanol or backwash by introducing water
46、into the bottom ofthe column and allowing it to escape at the top, or use bothprocedures. The rate of backwashing should be rapid enough toexpand the bed, but not allow loss of the resin.12. Calibration and Standardization12.1 Prepare a series of thiocyanate standards containing0.0 to 2.0 mg SCN/Lby
47、 pipetting 0-(blank) to 40-mLaliquotsof standard thiocyanate solution into 200-mLvolumetric flasks.Dilute to volume with water and mix thoroughly.12.2 Acidify 150 mL of standard (or an aliquot of samplediluted to 150 mL) to pH 2 by the dropwise addition ofconcentrated nitric acid and pass it through
48、 the resin column ata flow rate not exceeding 20 mL/min (See 11.10-11.12).NOTE 3If it has been established that the sample contains nointerfering compounds, the use of the absorption column can be elimi-nated from both the standardization and sample procedures.12.3 Pour the 50 mL of collected eluate
49、 into a beaker, add2.5 mL of ferric nitrate solution, and mix.12.4 Within 5 min, determine the absorbance of the solutionat 460 nm in a 5.0-cm cell using water as a reference.D419308312.5 Calculate the slope and intercept of the curve. See14.1.1.12.6 A duplicate sample and known standard must beanalyzed each day that an analysis is performed.12.7 A blank and a spiked sample shall be analyzed eachday that an analysis is performed. Spiking shall be in accor-dance with that outlined in D 3856, D 5788 and D 5789. Theblank shall be low.12.8 One sample must be ana
