Determination of 14 haloketones in treated water using solid-phase microextraction and gas chromatography-mass spectrometry

Haloketones (HKs) are unregulated volatile disinfection by-products that show some potential risk even at low concentrations. While EPA Method 551.1 involves conventional liquid-liquid extraction and a complex series of steps, the simple scientific principles of solid-phase microextraction (SPME) in the headspace (HS) mode can be applied to ensure a solvent-free method to control these substances at appropriate levels. The 14 HKs (12 mL of water at pH ∼ 1.5) were extracted on a DVB/CAR/PDMS fibre in 15 min. After extraction, the analytes were desorbed at 250 °C in the GC-MS inlet. Parameters affecting the extraction/desorption steps were investigated to select the most favourable conditions in short times. The HS-SPME/GC-MS method demonstrated high extraction efficiency with low limits of detection of between 15 and 600 ng/L, good linearity in the range 0.05-2 μg/L to 100-2000 μg/L, and good repeatability (RSD below 7%, n = 11). The green method was validated with EPA 551.1, used for determining halogenated VOCs in water, with noticeable advantages in terms of sensitivity, simplicity and solvent consumption. The results obtained from the analysis of water taken from a treatment plant employing chlorine dioxide and chloramines as disinfectants showed that two HKs were formed after pre-oxidation and that the subsequent steps in the plant were ineffective for their removal. Finally, the analysis of tap and swimming pool water exhibited that the concentration and number of species formed is higher in the latter, which is in accordance with its higher concentration of residual chlorine and organic matter.