Abstract: GC-MS with purging and trapping was applied to the determination of butylxanthic acid and 27 volatile organic compounds (VOCs) in water. Acidity of the sample was adjusted with HCl (1+1). HP-VOC capillary chromatographic column was used for GC separation, and modes of full-scanning and selected ion monitoring were adopted in MS determination. Internal standard method was used for quantification. Detection limits of the 28 compounds found were in the range of 0.10-6.93 μg·L-1. Values of recovery found by standard addition method were in the range of 96.9%-110%, and values of RSD′s (n=6) in the range of 0.92%-11%.