The method described is applicable to the determination of benzene, methylbenzene (toluene), dimethylbenzenes (xylenes) and ethylbenzene (abbreviated hereafter to BTX) in homogeneous samples of water and waste water in concentrations above 2 μg/l. In samples that are organically polluted, the limit of determination may, depending on the matrix of the sample, be higher. High concentrations may be determined by diluting the sample. A number of further derivatives and nonpolar compounds with similar physical properties may also be determined by this method. The applicability of the method should be verified for the particular water sample