Measuring naphthenic acids concentrations in aqueous environmental samples by liquid chromatography

Naphthenic acids are found in wastewaters from petroleum refineries and oil sands extraction plants. Currently, the concentrations of these toxic carboxylic acids are determined by extracting them into methylene chloride and measuring the absorption of the carboxyl group by Fourier-transform infrared (FTIR) spectroscopy. An improved HPLC method, that is simpler and faster than the FTIR method, was used to detect the 2-nitrophenylhydrazides of the naphthenic acids at concentrations as low as 5 mg l−1. Analyses of 58 oil sands water samples showed that the naphthenic acids concentrations determined by FTIR were on average 11% higher than those determined by HPLC.