1、Designation: D 3792 05Standard Test Method forWater Content of Coatings by Direct Injection Into a GasChromatograph1This standard is issued under the fixed designation D 3792; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the yea
2、r of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 This test method is for the det
3、ermination of the totalwater content of waterborne paints. It has been evaluated forlatex systems (styrene-butadiene, poly(vinylacetate)-acrylic,acrylic), epoxy acrylic resin systems and acrylic systems. Theestablished working range of this test method is from 15 to90 %. There is no reason to believ
4、e that it will not work outsideof this range.1.2 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility
5、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:2D 1193 Specification for Reagent WaterE 180 Practice for Determining Precision Data of ASTMMethods for
6、 Analysis and Testing of Industrial Chemicals3. Summary of Test Method3.1 A suitable aliquot of whole paint is internally standard-ized, diluted with dimethylformamide, and then injected into agas chromatographic column containing a porous polymerpacking that separates water from other volatile comp
7、onents.4. Significance and Use4.1 In order to calculate volatile organic content (VOC) inwaterborne paints, it is necessary to know the water content.This gas chromatographic test method provides a relativelysimple and direct way to determine water content.5. Apparatus5.1 Gas ChromatographyAny gas-l
8、iquid chromato-graphic instrument equipped with a thermoconductivity detec-tor may be used. Temperature programming capability ispreferable, but isothermal operations may be adequate. SeeTable 1.5.2 ColumnThe column should be at least 1.22 m (4 ft) of3.2-mm (18-in.) outside diameter tubing of stainl
9、ess steel, orother suitable material, lined with a TFE-fluorocarbon coatingpacked with 60/80 mesh (180 to 250 m) porous polymerpacking material.3A longer 1.83 m (6-ft) column can be usedto improve resolution.5.3 IntegratorAny electronic integrator that can accu-rately quantify a gas chromatographic
10、peak is acceptable.Alternatively, a recording potentiometer with a full-scaledeflection of 1-10mV, full scale response time of2sorless andsufficient sensitivity and stability to meet the requirements of5.1.5.4 Liquid Charging DevicesMicro syringes of 510-Lcapacity with a precision of 60.01 L. Automa
11、tic injection ofsamples improves the precision of this test method.6. Column Conditioning6.1 ProcedureInstall the packed column in the gas chro-matographic unit leaving the exit end disconnected from thedetector. This will prevent any contamination of the detectorwith the column bleed.6.1.1 Set the
12、carrier gas flow rate at 20 to 30 mL/min if a3.2-mm (18-in.) outside diameter column is used. Purge thecolumn 5 or 10 min before heating.6.1.2 Heat the column from room temperature to 200C at5C/min and hold this temperature for at least 12 h (overnight).At the end of this time, heat the column at 5C
13、/min to 250C1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings, Materials, and Applications and is the direct responsibility ofSubcommittee D01.21 on Chemical Analysis of Paints and Paint Materials.Current edition approved Jan. 1, 2005. Published February
14、2005. Originallyapproved in 1979. Last previous edition approved in 1999 as D 3792 99.2For 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
15、 page onthe ASTM website.3HayeSep R (silanized), was used in the round robin. Any other porous polymerpacking or other column giving equivalent or superior performance may be used.These products are available from most gas chromatography suppliers and distribu-tors.1Copyright ASTM International, 100
16、 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.(the maximum temperature for this packing) and hold forseveral hours. Cool the column to room temperature andconnect to the detector.6.1.3 Reheat the column to 250C at 5C/min to observe ifthere is column bleed. Optimum
17、conditioning of this columnmay take several cycles of the heating program before a flatrecorder baseline is achieved.6.2 Before each calibration and series of determinations (ordaily) condition the column at 200C for 1 h with carrier gasflow and to eliminate any residual volatile compounds retainedo
18、n the column.7. Reagents and Materials7.1 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 on Analytical Reagents of the American Chemical Society,where such specific
19、ations 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.7.2 Purity of WaterUnless otherwise indicated, referenceto water shall be understood to mean reagent wat
20、er conformingto Type II of Specification D 1193.7.3 Carrier GasHelium of 99.995 % or higher purity.High-purity nitrogen may also be used.NOTE 1Care should be taken that any moisture that may be present inthe carrier gas is eliminated through the use of a suitable carrier gaspurifier. Trace levels of
21、 water will accumulate on the column at low oventemperatures and may affect the reproducibility as well as the accuracy ofthe determination.7.4 Dimethylformamide (DMF) (Anhydrous) gas chroma-tography, spectrophotometric quality (See Note 2).7.5 2-Propanol (Anhydrous) (Isopropanol)See Note 2.7.6 Meth
22、anol (Anhydrous)See Note 2.7.7 Septum Sample Vials, 10-mL capacity withfluorocarbon-faced septa are preferred.7.8 Molecular Sieve, 2A-3A, 8-12, mesh.NOTE 2Dry the DMF, 2-propanol and methanol with the molecularsieve. Verify the absence of water by analysis of the solvents by this GCmethod.8. Hazards
23、8.1 Dimethylformamide is hazardous. Check the suppliersMaterial Safety Data Sheet (MSDS) before use.9. Preparation of Apparatus9.1 Install the column in the chromatograph and establishthe operating conditions required to give the desired separation(see Table 1).9.2 Allow sufficient time for the inst
24、rument to reach equi-librium as indicated by a stable base line.9.3 Control the detector temperature so that it is constant towithin 1C without thermostat cycling, which causes anuneven baseline.9.4 Adjust the carrier-gas flow to a constant value.10. Calibration10.1 Using the information in Table 1
25、(as a guide), select theconditions of temperature and carrier gas flow that givebaseline resolution of the water and internal standard.4Reagent Chemicals, American Chemical Society Specifications , AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the
26、American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.TABLE 1 Suggested Instrument ConditionsDetector thermal conductivityColumn 1.22 m
27、 3 3.2 mm TFE-fluorocarbon coatingcoated stainless steelPacking 60/80 mesh porous polymerTemperatures, CSample inlet 240Detector 250ColumnInitial 140Final 240Program rate 40/minCarrier gas heliumFlow rate, ml/min 22.0-22.5Detector current 150 mASpecimen size 1-2 lFIG. 1 Typical ChromatogramD37920521
28、0.2 Determination of Relative Response Factors:10.2.1 Anhydrous 2-propanol or methanol is used as aninternal standard.510.2.2 The response factor to water relative to the internalstandard is determined by means of the following procedure.See Fig. 1 for a typical chromatogram. It is good practice tod
29、etermine the relative retention time daily or with each seriesof determinations. Failure of this value to remain relativelyconstant may indicate a chromatographic problem.10.2.3 Weigh about 0.9 g of water and 0.9 g of 2-propanolor appropriate amount of an alternate internal standard to 0.1mg into a
30、septum sample vial. Weigh 9.0 g of dimethylforma-mide (DMF) into the vial. If the DMF is anhydrous, simply add9 mL of it as weighing is not necessary.10.2.4 Inject a 1- or 2-l aliquot of the above solution intothe column and record the chromatogram. The retention orderand approximate retention times
31、 after the air peak are (1)water; (2) internal standard, and (3) DMF (see Fig. 1).10.2.5 Calculate the response factor for water by means ofthe following equation:R 5Wi! AH2O!WH2O! Ai!(1)where:Wi= weight of internal standard,WH2O= weight of water added,AH2O= area of water peak, andAi= area of intern
32、al standard peak.11. Procedure11.1 Weigh to 0.1 mg, 0.6 g of waterborne paint (see Note3) and 0.6 g of internal standard into a septum vial. Add 7.0 gof DMF into the vial. Seal the vial.NOTE 3Initially, each paint specimen should be analyzed to check forthe presence of methanol or isopropanol so tha
33、t the proper internalstandard can be used. Check each paint system to be analyzed forinterfering peaks. Coalescing agents do not interfere with this determina-tion.11.2 Shake the vials on a wrist action shaker or othersuitable device for 15 min. To facilitate settling of solids allowthe vials to sta
34、nd for 5 min just prior to injection into thechromatograph. Low-speed centrifugation may also be used.11.3 Inject a 1- or 2-L sample of the supernatant from theprepared solutions into the gas chromatograph. Record thechromatograms using the conditions described in Table 1.Make duplicate determinatio
35、ns.12. Calculations12.1 With the integrator set up to measure the area of thewater and the internal standard peaks, multiply each area by theappropriate attenuation factor to express the peak areas on acommon basis. Use of an electronic integrator is recommendedto obtain the best accuracy and precis
36、ion.12.2 Calculate the water concentration in the paint by meansof the following equation:H2O, % 5AH2O3 Wi3 100Ai3 Wp3 R(2)where:AH2O= area of water peak,Ai= area of internal standard,Wi= weight of internal standard,Wp= weight of paint, andR = response factor determined in 10.2.12.3 Report H2O, %, t
37、he mean of duplicate determinationsif the relative percent difference is 1.6 % or less. If the relativepercent difference between the two values is greater than1.6 %, repeat the determinations in duplicate.12.4 Correction for Water Content of Solvent:12.4.1 If the blank indicates the presence of a d
38、etectablepeak for water in the dimethylformamide used as solvent, makea correction in the calculation.12.4.2 The water content of the dimethylformamide deter-mined by either chromatography or preferably, Karl Fischertitration is used to make the correction. Calculate the watercontent due to the solv
39、ent by using the following equation:H2OS!,% Ws!P!100Wp(3)where:Ws= weight of dimethylformamide,Wp= weight of paint, andP = weight % of water in DMF/100.12.4.3 The water content of the paint in this case is thedifference between the total percent determined in 12.2 and thecorrection for the solvent w
40、ater content as determined in12.4.2.13. Precision and Bias613.1 The precision estimates are based on an interlaboratorystudy in which five different laboratories analyzed in duplicateon two days six samples of waterborne paints containing from34 to 76 % H2O. The results obtained were analyzed statis
41、ti-cally in accordance with Practice E 180. The within-laboratorycoefficient of variation was found to be 0.77 % relative at 27 dfand the between-laboratories coefficient of variation 1.72 %relative at 21 df. Based on these coefficients, the followingcriteria should be used for judging the acceptabi
42、lity of resultsat the 95 % confidence level.13.1.1 RepeatabilityTwo results, each the mean of dupli-cate deteminations, obtained by the same operator on differentdays should be considered suspect if they differ by more than2.8 % relative.13.1.2 ReproducibilityTwo results, each the mean of du-plicate
43、 determinations, obtained by operators in different labo-ratories should be considered suspect if they differ by morethan 5.0 % relative.5Select an internal standard compound that is not part of the paint or coatingformulation, or is not formed during the cure. Any compound that elutes free ofinterf
44、erences relatively close to water and gives approximately the same peak heightand peak width could be used. Both 2-propanol and methanol have been found to begood internal standard compounds. An alternative internal standard may beconsidered.6Supporting data are available from ASTM International Hea
45、dquarters. RequestRR: D01-1022 and D01-1027.D379205313.2 BiasBias cannot be determined because there are noaccepted standards for water content of coatings.14. Keywords14.1 gas chromatograph; water content of paints by gaschromatographyASTM International takes no position respecting the validity of
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48、ur comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is cop
49、yrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).D3792054
