Multiple Response for Determination of BTEX in Water Samples Produced Using Semipermeable Membranes for Passive Sampling

Supersaline waters are complex samples that require the use of sample preparation based on analyte separation. In the oil industry it is common to co-produce huge volumes of water with high salinity containing inorganic and organic substances (such as benzene, toluene, ethylbenzene and xylenes - BTEX), which may present a risk to aquatic life. The objective of this work is to use low-density polyethylene semipermeable membrane devices (SPMD) to monitor the presence of BTEX by high performance liquid chromatography with ultraviolet detection in samples of produced water using multivariate experimental planning based on the Doehlert matrix with two variables in the quantification stage. The use of the Doehlert matrix was proposed due to previous studies that demonstrated the transfer rates alteration of the analytes in supersaline enviroment and the possibility of these variables interaction. The previously optimized procedure consists of a closed system containing 50 mL of aqueous solution of the analytes/sample and a SPMD filled with 3 mL of acetonitrile as the acceptor phase immersed in the solution for 4h. The multivariate study model was obtained using the analytes concentration (0,25 – 0,75 mg L-1) and the salinity (15 – 150 ‰) as variables according to the experiments indicated by Doehlert matrix. The developed methodology was applied in real samples and the accuracy was obtained by recovery tests with good results which makes the method attractive for estimating the BTEX concentration in samples of produced waters.