The Environmental Protection Agency (EPA) requires that Disinfection by-products (DBPS) levels must be determined as part of the current regulatory testing; the trihalomethanes (THMs) are the indicator chemicals for the other DBPs. The long-used established USEPA method 551.1 has been employed by many researches: it involves a Liquid-liquid Extraction and analysis using Gas chromatography. This study makes some important modifications in the method of the Gas Chromatographic analysis for the determination of the trihalomethanes (THMs) levels in the drinking water of four Water Treatment Plants (WTPs) in Lagos and Ogun States of Southwest Nigeria. A total of One hundred and four raw and processed water samples were collected and analyzed between January and May, using HP-1ms Ultra Inert Agilent 7890A Gas Chromatograph (GC) with Autosampler Agilent 7683B equipped with an Electron Capture Detector (ECD). The modified split ratio reduced the level of contaminants in the GC column. The signal rate reduced to 5HZ enhanced better flow and separation of peaks. The multi-level calibration helped in obtaining accurate quantitative results. The results of the recovery test validate the method accuracy.
Akintokun et al. (Wed,) studied this question.