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Paint and Coatings Industry Standards
D6438 Standard Test Method for Acetone, Methyl Acetate, and Parachlorobenzotrifluoride Content of Paints, and Coatings by Solid Phase Microextraction-Gas Chromatography
In order to calculate the volatile organic content (VOC) of paints containing EPA exempt solvents, it is necessary to know the acetone, methyl acetate, or parachlorobenzotrifluoride content. This gas chromatographic test method provides a simple and direct way for measuring these solvents. Each analyte is measured with respect to a unique internal standard. For acetone, the internal standard used is acetone-d6, for methyl acetate it is methyl acetate-d3, and for PCBTF it is metachlorobenzotrifluoride (MCBTF). These unique analyte/internal standard pairs behave very nearly as single solvents with respect to evaporation rate and adsorption rate onto a coated silica fiber (SPME) but are separable on a gas chromatograph (GC) capillary column. The only critical analytical technique required for successfully performing this test method is the ability of an analyst to weigh a paint sample and internal standard, corresponding to the analyte of interest, into a septum capped vial. After weighing, solvent evaporation has no effect on the final value of the determination. Since whole paint is not injected into the gas chromatograph, the analytical system is never compromised.
1.1 This test method is for the determination of acetone, methyl acetate, or parachlorobenzotrifluoride (PCBTF), or combination of any of the three, in paints and coatings, by solid phase microextraction (SPME) headspace sampling, and subsequent injection into a gas chromatograph. It has been evaluated for cellulose nitrate, acrylic, and urethane solvent-borne systems. The established working range of this test method is: acetone, 28 to 90 %; methyl acetate, 12 to 22 %; parachlorobenzotrifluoride, 10 to 17 %. There is no reason to believe that it will not work outside these ranges. A minor modification of this test method would make it suitable for the analysis of the same analytes in water-borne coatings (see Note 1).
Note 1—Water-borne paints are internally standardized and diluted with water followed by addition of solid sodium chloride.
