1、Designation: D3792 16Standard Test Method forWater Content of Coatings by Direct Injection Into a GasChromatograph1This standard is issued under the fixed designation D3792; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、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 test method is for the d
3、etermination 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 beli
4、eve 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 theresponsibilit
5、y 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:2D1193 Specification for Reagent WaterE180 Practice for Determining the Precision of ASTMMethods for
6、Analysis and Testing of Industrial and Spe-cialty Chemicals (Withdrawn 2009)33. Summary of Test Method3.1 A suitable aliquot of whole paint is internallystandardized, diluted with dimethylformamide, and then in-jected into a gas chromatographic column containing a porouspolymer packing that separate
7、s water from other volatilecomponents.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. Apparatus
8、5.1 Gas ChromatographyAny gas-liquid 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.) ou
9、tside diameter tubing of stainless steel, orother suitable material, lined with a TFE-fluorocarbon coatingpacked with 60/80 mesh (180 to 250 m) porous polymerpacking material.4A longer 1.83 m (6-ft) column can be usedto improve resolution.5.3 IntegratorAny electronic integrator that can accu-rately
10、quantify a gas chromatographic 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
11、 a precision of 60.01 L. Automatic 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
12、the column bleed.6.1.1 Set the 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.1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings, Materials, and Applications and is t
13、he direct responsibility ofSubcommittee D01.21 on Chemical Analysis of Paints and Paint Materials.Current edition approved April 1, 2016. Published May 2016. Originallyapproved in 1979. Last previous edition approved in 2015 as D3792 05 (2015).DOI: 10.1520/D3792-16.2For referenced ASTM standards, vi
14、sit 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.3The last approved version of this historical standard is referenced onwww.astm.org.4HayeSep R
15、(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.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West
16、 Conshohocken, PA 19428-2959. United States16.1.2 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/min to 250C(the maximum temperature for this packing) and hold forseveral hours. Cool the co
17、lumn 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 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 det
18、erminations (ordaily) condition the column at 200C for 1 h with carrier gasflow and to eliminate any residual volatile compounds retainedon the column.7. Reagents and Materials7.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall
19、reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.5Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening
20、 theaccuracy of the determination.7.2 Purity of WaterUnless otherwise indicated, referenceto water shall be understood to mean reagent water conformingto Type II of Specification D1193.7.3 Carrier GasHelium of 99.995 % or higher purity.High-purity nitrogen may also be used.NOTE 1Care should be taken
21、 that any moisture that may be present inthe carrier gas is eliminated through the use of a suitable carrier gaspurifier. Trace levels of water will accumulate on the column at low oventemperatures and may affect the reproducibility as well as the accuracy ofthe determination.7.4 Dimethylformamide (
22、DMF) (Anhydrous) gaschromatography, spectrophotometric quality (See Note 2).7.5 2-Propanol (Anhydrous) (Isopropanol)See Note 2.7.6 Methanol (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 DM
23、F, 2-propanol and methanol with the molecularsieve. Verify the absence of water by analysis of the solvents by this GCmethod.8. Hazards8.1 Dimethylformamide is hazardous. Check the suppliersSafety Data Sheet (SDS) before use.9. Preparation of Apparatus9.1 Install the column in the chromatograph and
24、establishthe operating conditions required to give the desired separation(see Table 1).9.2 Allow sufficient time for the instrument to reach equi-librium as indicated by a stable baseline.9.3 Control the detector temperature so that it is constant towithin 1C without thermostat cycling, which causes
25、 anuneven baseline.9.4 Adjust the carrier-gas flow to a constant value.10. Calibration10.1 Using the information in Table 1 (as a guide), select theconditions of temperature and carrier gas flow that givebaseline resolution of the water and internal standard.10.2 Determination of Relative Response F
26、actors:5Reagent 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 LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pha
27、rmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.TABLE 1 Suggested Instrument ConditionsDetector thermal conductivityColumn 1.22m3.2mmTFE-fluorocarbon coatingcoated stainless steelPacking 60/80 mesh porous polymerTemperatures, CSample inlet 240Detector 250Col
28、umnInitial 140Final 240Program rate 40/minCarrier gas heliumFlow rate, ml/min 22.0-22.5Detector current 150 mASpecimen size 1-2 lFIG. 1 Typical ChromatogramD3792 16210.2.1 Anhydrous 2-propanol or methanol is used as aninternal standard.610.2.2 The response factor to water relative to the internalsta
29、ndard is determined by means of the following procedure.See Fig. 1 for a typical chromatogram. It is good practice todetermine 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 Weig
30、h 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 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 aliquo
31、t of the above solution intothe column and record the chromatogram. The retention orderand approximate retention times after the air peak are (1)water; (2) internal standard, (see Note 3), and (3) DMF (seeFig. 1).10.2.5 Calculate the response factor for water by means ofthe following equation:R 5Wi!
32、AH2O!WH2O!Ai!(1)where:Wi= weight of internal standard,WH2O= weight of water added,AH2O= area of water peak, andAi= area of internal standard peak.NOTE 3Initially, each paint specimen should be analyzed to check forthe presence of methanol or isopropanol so that the proper internalstandard can be use
33、d. Check each paint system to be analyzed forinterfering peaks. Coalescing agents do not interfere with this determina-tion.11. Procedure11.1 Weigh to 0.1 mg, 0.6 g of waterborne paint and 0.6 gof internal standard into a septum vial. Add 7.0 g of DMF intothe vial. Seal the vial.11.2 Shake the vials
34、 on a wrist action shaker or othersuitable device for 15 min, (dry mixing beads added to the vialshave proved beneficial with viscous samples). To facilitatesettling of solids allow the vials to stand for 5 min just prior toinjection into the chromatograph. Low-speed centrifugationmay also be used.1
35、1.3 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 determinations.12. Calculations12.1 With the integrator set up to measure the area of thewater and the internal sta
36、ndard 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 precision.12.2 Calculate the water concentration in the paint by meansof the following equation:H2O,%5AH2O3 W
37、i3100Ai3 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, %, the mean of duplicate determinationsif the relative percent difference is 1.6 % or less. If the relativeper
38、cent 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 detectablepeak for water in the dimethylformamide used as solvent, makea correction in the calculation.12.4
39、.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 solvent by using the following equation:H2OS!,%Ws!P!100Wp(3)where:Ws= weight of dimethylformamide,Wp= weight o
40、f 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 water content as determined in12.4.2.13. Precision and Bias713.1 The precision estimates are based on an int
41、erlaboratorystudy 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 statisti-cally in accordance with Practice E180. The within-laboratorycoefficient of variation was found to be 0.
42、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 acceptability of resultsat the 95 % confidence level.13.1.1 RepeatabilityTwo results, each the mean of dupli-cate det
43、erminations, obtained by the same operator on differentdays should be considered suspect if they differ by more than1.6 % relative.6Select 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 ofinterference
44、s 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.7Supporting data have been filed at ASTM International Headquart
45、ers and maybe obtained by requesting Research Report RR:D01-1022 and RR:D01-1027.Contact ASTM Customer Service at serviceastm.org.D3792 16313.1.2 ReproducibilityTwo results, each the mean of du-plicate determinations, obtained by operators in different labo-ratories should be considered suspect if t
46、hey differ by morethan 5.0 % relative.13.2 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 any patent rig
47、hts asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any
48、 time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments wi
49、ll 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 copyrighted 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 (p
