Experimental Evaluation of Preservation Techniques for Benzene, Toluene, Ethylbenzene, and Total Xylenes in Water Samples.

An experiment was designed to address the validity of the prescribed maximum allowable holding-time limit of 14 days when acidified at < 2 pH and maintained at 4°C to prevent significant loss of benzene, toluene, ethyl benzene, and xylenes (BTEX) in preserved water samples. Preservation methods prescribed by the United State Environmental Protection Agency were used as well as adaptions of that procedure to determine stability between 3 and 21 days. Water samples preserved at 4°C and pH of < 2 with hydrochloric acid did not result in unacceptable (> 15%) BTEX losses during the study as defined by procedures and statistical methods described by the American Society for Testing and Materials International. In addition, water samples preserved only with acid (pH < 2) at ambient temperatures (20-27°C) also provided acceptable results during the 21-day study. These results have demonstrated the acceptability of BTEX data derived from water samples exceeding the standard holding-time and/or temperature limits.