Headspace gas chromatography-mass spectrometry for rapid determination of halonitromethanes in tap and swimming pool water.

Halonitromethanes (HNMs) are one of the most cytotoxic and genotoxic classes found among the unregulated disinfection by-products formed by the reaction of chemical disinfectants with natural organic matter in water. Typical methods used to determine these compounds in water (mainly trichloronitromethane) are based on the Environmental Protection Agency (EPA) method 551.1 using liquid-liquid extraction. A fast and straightforward method for the determination of the nine HNMs in water has been developed using a static headspace (HS) coupled with gas chromatography-mass spectrometry (GC-MS). Important parameters controlling headspace extraction were optimised to obtain the highest sensitivity: 250 μL of methyl tert-butyl ether (as a chemical modifier) and 6 g of anhydrous sodium sulphate were added to the water sample; an oven temperature of 80 °C and an equilibration time of 20 min were also selected. The addition of a chemical modifier favoured the volatilisation of all HNMs, increasing their signals up to approximately four times. Under optimum conditions, the method developed provides limits of detection between 0.03 and 0.60 μg/L and a relative standard deviation of ~6.0%. The developed method was validated and then compared with the reference method EPA 551.1 for the analysis of tap and swimming pool water. A good agreement in the results was observed, which corroborated the good performance of the proposed HS-GC-MS method.