Validation of a robust LLE-GC-MS method for determination of trihalomethanes in environmental samples

An analytical liquid-liquid extraction-gas chromatography-mass spectrometry (LLE-GC-MS) method was developed and validated for the determination of trihalomethanes (THMs) in environmental samples. The compounds studied were trichloromethane (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM), and tribromomethane (TBM). The calibration curves for the THMs showed high linearity in the range of 1-1000 μg L^-1. Studies of intra-day and inter-day precision, limit of detection (LOD), limit of quantification (LOQ), accuracy, and recovery were performed with low (10 μg L^-1), medium (40 μg L^-1), and high (200 μg L^-1) concentrations of THMs. The intra-day and inter-day precision RSD varied in the ranges of 0.17-6.95% and 0.26-15.70%, respectively. No statistical differences were observed between the analysis of the concentration of certified reference materials (CRM 4M8140-U) and the values reported by CRM, indicating the good accuracy of the proposed method. The recovery was 88.75-119.21%. The LOD and LOQ were smaller than 0.13 and 0.40 μg L^-1. Compared with reported LLE-GC-MS methods, the validated method had similar LOD and enhanced LOQ, precision, accuracy, and recovery. Also, the method is robust, selective to THMs, and the total time for the extraction and GC separation of THMs is about 18 min. The method was useful for detecting and quantifying low concentrations of TCM (40-80 μg L^-1) formed by water chlorination in the presence of Microcystis aeruginosa cyanobacteria, thus demonstrating its applicability for monitoring THMs in real samples.