RESUMEN
Several groups of organic compounds have emerged as being particularly relevant as environmental pollutants, including disinfection by-products (DBPs). Haloketones (HKs), which belong to the unregulated volatile fraction of DBPs, have become a priority because of their occurrence in drinking water at concentrations below 1µg/L. The absence of a comprehensive method for HKs has led to the development of the first method for determining fourteen of these species. In an effort to miniaturise, this study develops a micro liquid-liquid extraction (MLLE) method adapted from EPA Method 551.1. In this method practically, the whole extract (50µL) was injected into a programmed temperature vaporiser-gas chromatography-mass spectrometer in order to improve sensitivity. The method was validated by comparing it to EPA Method 551.1 and showed relevant advantages such as: lower sample pH (1.5), higher aqueous/organic volume ratio (60), lower solvent consumption (200µL) and fast and cost-saving operation. The MLLE method achieved detection limits ranging from 6 to 60ng/L (except for 1,1,3-tribromo-3-chloroacetone, 120ng/L) with satisfactory precision (RSD, â¼6%) and high recoveries (95-99%). An evaluation was carried out of the influence of various dechlorinating agents as well as of the sample pH on the stability of the fourteen HKs in treated water. To ensure the HKs integrity for at least 1 week during storage at 4°C, the samples were acidified at pH â¼1.5, which coincides with the sample pH required for MLLE. The green method was applied to the speciation of fourteen HKs in tap and swimming pool waters, where one and seven chlorinated species, respectively, were found. The concentration of 1.1-dichloroacetone in swimming pool water increased â¼25 times in relation to tap water.
Asunto(s)
Acetona/análogos & derivados , Acetona/análisis , Contaminantes Químicos del Agua/análisis , Agua Potable/análisis , Cromatografía de Gases y Espectrometría de Masas/métodos , Tecnología Química Verde , Halogenación , Humanos , Límite de Detección , Microextracción en Fase Líquida/métodos , Purificación del AguaRESUMEN
This paper describes the first micro liquid-liquid extraction (MLLE) gas chromatography-mass spectrometry (GC-MS) method for the speciation of emerging iodinated acetic acids, along with conventional chlorinated and brominated acids in water. The haloacetic acids (HAAs) were derivatised using 3 reagents for their methylation, both in aqueous and organic media. The acidic methanol derivatisation in aqueous medium provided the best efficiency, requiring minimal sample manipulation. The derivatisation yield was improved through the use of microwave energy that drastically reduced reaction time (2 min). The HAA methyl esters were finally extracted using 250 µL of methyl tert-butyl ether. This MLLE combined with the use of a large-volume sample injection coupled to a programmed temperature vaporiser-GC-MS improved the sensitivity of the method and minimised the generation of hazardous residues in accordance with the principles of "Green Chemistry". Detection and quantification limits (excepting tribromoacetic acid) within the range of 0.01-0.15 µg/L and 0.03-0.5 µg/L, respectively, were obtained and the relative standard deviation was lower than 10%. The eco-friendly method was applied to the speciation of the 13 HAAs in treated (chlorinated and chloraminated water) and untreated water. Up to 8 HAAs were found at detectable levels in treated water. The highly toxic monoiodoacetic acid was detected in almost all the chloraminated water.