Optimization of gas chromatographic analysis of halogenated acids in drinking water using full factorial experimental design

An analytical method based on gas chromatography–mass spectrometry (GC–MS) has been developed to determine non-volatile fraction of disinfection by-products (DBP) in drinking water. Solid phase extraction (SPE) with tri-methyl-ammonium chlorine (TMA-Cl) cartridges is followed by derivatization of desired analyte in the eluted extract. The studied factors are elution volume, methy-tertiary-butyl ether (MTBE) volume and derivatization time. Experimental design was used to investigate and subsequently used to optimize the elution volume of derivatizing agent (10% acidic methanol), MTBE volume and derivatization time for haloacetic acids (HAAs) extraction in the water sample. Regression models and desirability functions were applied to find an experimental setup for acquiring the highest global extraction yield of HAAs. The elution volume and derivatization time were the only statistically significant factors from this study. In the final optimized conditions, the procedure was applied to the SPE–GC–MS analysis of HAAs in water samples with better figures of merit. This modified method has advantage over the EPA method 552.1.