In a discussion of the sampling and determination of azelaic-acid in air, air samples of azelaic-acid (nonanedioic-acid) were collected on polyvinyl-chloride (9002862) (PVC) filters, extracted with ethanol derivatized with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA), containing 1% trimethylchlorosilane (TMCS) and analyzed by gas/liquid chromatography. The esterification product is the trimethylsilyl-ester, which is different from the methyl ester usually chosen in the esterification processes. A calibration curve was used to determine the azelaic-acid content in the filter samples. The detection limit was 1 microgram per sample. Results indicate that the analytical method can be applied to other monocarboxylic and dicarboxylic acids. Azelaic-acid and its derivatives are employed widely in the plastics and synthetic fiber industry, in the preparation of hydraulic fluids and lubricants, and as plasticizers in rubber (9006046). Short term toxicological animal studies have shown that azelaic-acid is not toxic but is considered as an irritant.