1、Designation: D3624 85a (Reapproved 2015)Standard Test Method forLow Concentrations of Mercury in Paint by AtomicAbsorption Spectroscopy1This standard is issued under the fixed designation D3624; the number immediately following the designation indicates the year oforiginal adoption or, in the case o
2、f revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope1.1 This tes
3、t method covers the determination of the contentof mercury in the range between 10 and 1000 ppm (mg/kg)present in liquid coatings, coatings vehicles, or in dried filmsobtained from previously coated substrates. There is no reasonto believe that higher levels could not be determined by thistest metho
4、d, provided that appropriate dilutions and adjust-ments in specimen size and reagent quantities are made.1.2 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
5、 health practices and determine the applica-bility of regulatory limitations prior to use. Specific hazardstatements are given in Section 7 and 9.1.1.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent Water3. Summary of Test Method3.1 The sample of liquid coating or dried fil
6、m is weighedinto a polytetrafluoroethylene (PTFE)-lined acid decomposi-tion vessel and digested at an elevated temperature usingsulfuric and nitric acids. Use of a sealed acid decompositionvessel prevents loss of mercury during the digestion. Thedigested sample is diluted to a known volume with wate
7、r andthe concentration of mercury is determined using a cold-vapor,atomic absorption technique.4. Significance and Use4.1 The permissible level of heavy metals in certain coat-ings is specified by governmental regulatory agencies. This testmethod provides a fully documented procedure for determining
8、low concentrations of mercury present in both water andsolvent-reducible coatings to determine compliance.5. Apparatus5.1 Atomic Absorption SpectrophotometerAny commer-cial instrument having an open sample presentation area inwhich to mount the absorption cell or an instrument designedspecifically f
9、or the measurement of mercury using the coldvapor technique.5.2 Recorder, 0to10mV.5.3 Mercury Source Lamp.5.4 Absorption CellStandard spectrophotometer cells 100mm long, having quartz end windows may be used. Prior touse, the cell must be positioned in the optical path of thespectrophotometer and he
10、ld in place by suitable clamps orstraps. The cell should be carefully aligned both vertically andhorizontally to give the maximum transmittance.5.5 Reduction VesselCylindrical gas washing bottle, 250-mL, equipped with a coarse (40 to 60-m) fritted glass inlettube and a standard-taper glass stopper.
11、Polyethylene or poly-(vinyl chloride) tubing may be used for connecting the reduc-tion vessel to the absorption cell.5.6 Flowmeter, capable of measuring a gas flow of 1 L/min.5.7 Drying TubeApproximately 150 by 20-mm (6 by34-in.) glass tube filled with magnesium perchlorate. The tubeshould be filled
12、 each day that it is in use, and the Mg(ClO4)2should be replaced whenever it becomes saturated (carefullyobserve after each analysis).NOTE 1Use of an indicator desiccant at the exit end of the tube willmake this observation easier.5.8 Water Vapor TrapA second 250-mL gas washingbottle (the same as us
13、ed for the reduction vessel). If preferred,a 250-mL Erlenmeyer vacuum flask fitted with a one-holestopper and 200 mm of 5-mm outside diameter glass tubing,may be substituted. (Fig. 1)1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings, Materials, and Applic
14、ations and is the direct responsibility ofSubcommittee D01.21 on Chemical Analysis of Paints and Paint Materials.Current edition approved June 1, 2015. Published June 2015. Originallyapproved in 1977. Last previous edition approved in 2010 as D3624 85a (2010).DOI: 10.1520/D3624-85AR15.2For reference
15、d 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.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Cons
16、hohocken, PA 19428-2959. United States15.9 Mercury TrapA 250-mL Erlenmeyer vacuum flaskcontaining 75 mL of 10 % sulfuric acid and 75 mL of 0.1 Npotassium permanganate solution to absorb the mercury vaporafter analysis.5.10 Circulating Oven, maintained at 140 6 5C.5.11 Acid Decomposition Vessel, with
17、 25-mL PTFE diges-tion cup.35.12 Volumetric Flasks, 100, 250, and 1000-mL.5.13 Paint Shaker.5.14 Paint Draw-Down Bar.6. Reagents6.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of
18、the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.4Other 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.6.2 Purity of
19、WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent water conformingto Type II of Specification D1193.6.3 Hydroxylamine Hydrochloride Solution (100 g/L)Dissolve 10 g of NH2OHHCl in 100 mL of water. Transfer aportion of this solution to a small dropping bottle.6.4
20、Mercury Solution, Stock (1 mg/mL)Dissolve 0.1354 gof HgCl2in 50 mL of water. Carefully add 5 mL of concen-trated H2SO4and 3 mL of concentrated HNO3and dilute to100 mL. This solution contains 1000 g/mL of mercury.6.5 Mercury Standard, Working (0.1 g/mL)Make succes-sive dilutions of the stock mercury
21、solution to obtain a workingstandard containing 0.1 mg/L (0.1 g/mL), maintaining aconcentration of 5 % H2SO4and 3 % HNO3by volume, in thediluted solutions. The working mercury standard and thedilutions of the stock mercury solution should be preparedfresh each day that it is used.6.6 Nitric Acid (sp
22、 gr 1.42)Concentrated nitric acid (HNO3).6.7 Nitrogen.6.8 Potassium Permanganate Solution (0.1 N)Dissolve15.8 g of KMnO4in water and dilute to 1 L.6.9 Stannous Chloride Solution (100 g/L)Dissolve 25 g oftin (II) chloride (SnCl2) by adding it to 60 mL of concentratedHCl (sp gr 1.19) and warming on a
23、hotplate. When all of theSnCl2has dissolved, transfer to a 250-mL volumetric flask anddilute to volume with water. Mix well. This solution should beprepared fresh each week that it is used.6.10 Sulfuric Acid (sp gr 1.84)Concentrated sulfuric acid(H2SO4).6.11 Sulfuric Acid (1+9)Carefully mix 1 volume
24、 of H2SO4(sp gr 1.84) into 9 volumes of water.7. Hazards7.1 Concentrated nitric and sulfuric acids are corrosive andmay cause severe burns of the skin or eyes. The vapor fromconcentrated nitric acid is irritating to mucous membranes. Usecare in handling these acidic substances. Refer to suppliersMat
25、erial Safety Data Sheet.7.2 Mercury and its compounds are harmful and accumulatein the aquatic environment. Mixtures containing mercurycompounds should not be flushed down a drain, but disposed ofas hazardous waste.7.3 Use only a rubber bulb aspirator for pipetting liquids.3The sole source of supply
26、 of an acid decomposition vessel, Catalog No. 4745,known to the committee at this time is the Parr Instrument Co., 211 Fifty-third St.,Moline, IL 61265. If you are aware of alternative suppliers, please provide thisinformation to ASTM International Headquarters. Your comments will receivecareful con
27、sideration at a meeting of the responsible technical committee,1whichyou may attend.4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for
28、LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.FIG. 1 ApparatusD3624 85a (2015)28. Calibration and Standardization8.1 Assemble the various components, as illustrated in Fig.1 if an
29、 atomic absorption spectrophotometer is used, or preparethe instrument for operation if a commercial mercury analyzeris being used.NOTE 2Be sure that all glassware has been thoroughly cleaned andrinsed with reagent water prior to use.8.2 Operational instructions for atomic absorption spectro-photome
30、ters and commercial mercury analyzers vary withdifferent models. Consult the manufacturers literature forestablishing optimum conditions for the specific instrumentused.8.3 With the apparatus empty, stabilize the recorder baseline while maintaining a flowrate of 250 mL of nitrogen perminute.8.4 Tran
31、sfer 0, 5, 10, 15, and 20-mL aliquots of the workingmercury standard (containing 0 to 2 g of mercury) to a seriesof 250-mL gas washing bottles. Add enough water to eachbottle to make a total volume of 100 mL. Add 5 mL of H2SO4and 3 mL of HNO3to each bottle and mix thoroughly. Makedropwise additions
32、of 0.1 N KMnO4solution to each bottle inturn until a pink color persists for at least 30 s (1 mL is usuallysufficient). Add exactly 1 mL of NH2OHHCl solution drop-wise to each bottle and swirl until the pink color is discharged.8.5 Add 10 mL of SnCl2solution to the bottle containing noadded working
33、mercury standard. Immediately insert the frittedglass inlet tube, making sure that the stopper provides a goodseal. Adjust the nitrogen flow rate to a previously determinedoptimum setting (see Note 3) and take a reading. A blank valuegreater than 5 % of full scale indicates either reagent orapparatu
34、s contamination. When the recorder, meter, or otherreadout device reaches a maximum value, it should be imme-diately zeroed. Repeat this blank determination until a steady,repeatable zero value is obtained at the maximum response.NOTE 3Optimum nitrogen flow rate may be determined by analyzing1-g qua
35、ntities of mercury (10 mL of working mercury standard diluted to100 mL) by this procedure, varying the flow rate to determine theoptimum mercury signal and time required for analysis. Then use thisoptimum flow rate for all analyses, unless a change is made in the volumeor geometry of the apparatus.8
36、.6 Similarly treat each standard solution made up in 8.4,recording the maximum peak height for each. When therecorder pen begins dropping, remove the fritted glass inlettube from the gas washing bottle and insert it into anotherbottle containing only water. Continue nitrogen flow until theabsorbance
37、 reaches zero, when the apparatus is ready for thenext solution.NOTE 4Because mercury vapor is very toxic, take precautions toavoid its inhalation. Bubble the exhaust from the absorption cell throughan absorbing solution consisting of equal volumes of 0.1 N KMnO4solution and 10 % H2SO4(see Fig. 1).
38、Do not discharge the absorbingsolution into a sewer system.8.7 Construct a standard curve by plotting peak heightsversus micrograms of mercury. Peak heights used should be themean of duplicate determinations on each solution.9. Procedure9.1 If the sample is a liquid coating, mix it untilhomogeneous,
39、 preferably on a mechanical paint shaker. Pre-pare at least two replicate specimens by weighing to 0.1 mg bydifference from a dropping bottle or syringe, 100 to 200 mg ofthe mixed paint into the PTFE insert of the acid decompositionvessel. Place the insert in an oven set at 60C (140F) for 1 hto remo
40、ve all volatiles.9.1.1 CautionIf the solvent present in a sample is notremoved prior to the digestion step as recommended, poten-tially dangerous pressures may result when the vessel is heatedat 140C.9.2 If the sample consists of dried film, coarsely grind it andweigh 50 to 100 mg by difference from
41、 a weighing bottle intothe digestion vessel.NOTE 5Recover dried paint films from previously coated substrates(being careful not to remove any underlying material from the substrate)or prepare in the laboratory from liquid samples. For the laboratorypreparation, flow some of the well-mixed sample ont
42、o a clean glass plate.The use of a paint draw-down bar is recommended to obtain a uniform wetfilm thickness not exceeding 2 mils (50 m). Allow the film to dry in anoven at 60C for a minimum of 1 h. Scrape the dried film off the glassplate, preferably with a single-edge razor blade.9.3 Pipet 5 mL of
43、concentrated H2SO4and3mLofconcentrated HNO3into the decomposition vessel insert, usinga fume hood for the operation. Seal the vessel tightly and placein the circulating oven at 140C for 112 h. Remove the vesselfrom the oven and allow it to cool slowly to room temperature.NOTE 6Do not assist cooling
44、by putting the vessel in a refrigerator orfreezer, or by submerging it in a cooling liquid; otherwise mercury lossesmay occur due to leakage of pressurized gases resulting from unevencontraction of the bomb parts and PTFE seal.NOTE 7Analysis of the digested specimen (9.4 9.7) should becompleted with
45、in 1 h after the digestion step.9.4 When completely cooled, carefully unseal the vessel ina fume hood, add approximately 5 mL of cold water and swirlgently. Quantitatively transfer the contents to a 100-mL beaker,using several small quantities of water. Dilute to a volume of30 to 40 mL and filter th
46、rough filter paper directly into a100-mL volumetric flask. Wash the residue on the filter paperseveral times with small volumes of water. Dilute to volumewith water and mix thoroughly.9.5 Transfer an aliquot of each digested specimen contain-ing not over 2 g of mercury to a 250-mL gas washing bottle
47、.Add enough water to make a total volume of 100 mL. To eachbottle, add 5 mL of concentrated H2SO4and3mLofconcentrated HNO3and mix thoroughly.NOTE 8If large aliquots are taken for analysis, reduce the amount ofadded H2SO4and HNO3proportionately to compensate for the amountspresent in the digested sol
48、utions.9.6 Proceed with the addition of KMnO4,NH2OHHCl, andSnCl2solutions as described in 8.4 and 8.5. Record themaximum peak height for each solution.9.7 If the response obtained is above or below the responseobtained for the standards (8.7), repeat 9.5 and 9.6 using anappropriate aliquot size. Det
49、ermine the concentration of mer-cury present in microgram per millilitre from the calibrationcurve.D3624 85a (2015)310. Calculation10.1 Calculate the mean concentration of mercury in thesample as follows:mercury in sample, ppm mg/kg! 5 100 3 C!/F 3 S! (1)where:C = concentration of mercury in aliquot used, g/mL,F = dilution factor from 9.5 (aliquot volume used), andS = grams of sample.11. Report11.1 Report the mercury content in the material being testedand whether the analysis was conducted on a liquid coating ora dried film.12. Prec
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