Objective To examine the efficiency of different solvents and dilution ratios on extracting benzene from polyurethane varnish.
Methods Using carbon disulfide, n-hexane, ethyl acetate, tetrahydro-furan, and methanol as diluting solvent candidates, samples were diluted in selected proportions (1+2, 1+4, 1+6, 1+8, 1+10), then added with 10 μg/mL standard benzene solvent. Determination was performed by capillary gas chromatography with free fatty acid phase (FFAP) capillary column and hydrogen flame ionization detector (FID).
Results Good baseline separation was achieved by selecting carbon disulfide as solvent and the related detection limit for benzene was 0.008 4 μg/mL, and the quantitative limit was 0.028 μg/mL. The recoveries of benzene with varying carbon disulfide proportions were between 80.9%-96.1%, the relative standard deviation (RSD) was in the range of 1.15%-9.52%, the appropriate dilution level should be greater than (1+8). The general standard deviations of samples were all less than 5% of their concentrations with the confidence limit of 0.96.
Conclusion Sample recovery and reproducibility could be reduced by lower dilution level. The benzene determination in described optimal dilution ratio provides ideal precision and sufficient accuracy.
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