Simultaneous analysis of 10 trihalomethanes at nanogram per liter levels in water using solid-phase microextraction and gas chromatography mass-spectrometry

Abstract

Trihalomethanes are predominantly formed during disinfection of water via reactions of the oxidant with natural organic matter. Even though chlorinated and brominated trihalomethanes are the most widespread organic contaminants in drinking water, when iodide is present in raw water iodinated trihalomethanes can also be formed. The formation of iodinated trihalomethanes can lead to taste and odor problems and is a potential health concern since they have been reported to be more toxic than their brominated or chlorinated analogs. Currently, there is no published standard analytical method for I-THMs in water. The analysis of 10 trihalomethanes in water samples in a single run is challenging because the iodinated trihalomethanes are found at very low concentrations (ng/L range), while the regulated chlorinated and brominated trihalomethanes are present at much higher concentrations (above μg/L). An automated headspace solid-phase microextraction technique, with a programmed temperature vaporizer inlet coupled with gas chromatography-mass spectrometry, was developed for routine analysis of 10 trihalomethanes i.e. bromo-, chloro- and iodo-trihalomethanes in water samples. The carboxen/polydimethylsiloxane/divinylbenzene fiber was found to be the most suitable. The optimization, linearity range, accuracy and precision of the method are discussed. The limits of detection range from 1 ng/L to 20 ng/L for iodoform and chloroform, respectively. Matrix effects in treated groundwater, surfacewater, seawater, and secondary wastewater were investigated and it was shown that the method is suitable for the analysis of trace levels of iodinated trihalomethanes in a wide range of waters. The method developed in the present study has the advantage of being rapid, simple and sensitive. A survey conducted throughout various process stages in an advanced water recycling plant showed the presence of iodinated trihalomethanes at ng/L levels.

Simultaneous and high-throughput analysis of iodo-trihalomethanes, haloacetonitriles, and halonitromethanes in drinking water using solid-phase microextraction/gas chromatography-mass spectrometry: an optimization of sample preparation

“…As shown in Fig. 1, the DVB/CAR/PDMS fiber exhibited a better extraction efficiency, and it was similar to that obtained using the Carbowax/DVB fiber, which was found to be ten times lower than that of DVB/CAR/PDMS for DCIM and BCIM by Silva et al [17]. 85 m PA provides a maximum extraction capacity only for BDIM, while for TIM, the extraction efficiency is less than that of DVB/CAR/PDMS; and 65 m PDMS/DVB have similar extraction efficiencies for BDIM and TIM.…”

“…S1). These results indicate that the PDMS fiber is not the best coating for five Iodo-THMs (DCIM, BCIM, DBIM, CDIM, and TIM) because of its low capacity to extract [16,17]. The 7 and 30 m PDMS fibers, which are relatively thick, are not efficient for adsorbing Iodo-THMs and their capacity is less than those of 75 and 85 m CAR/PDMS (except for TIM) and five THMs [18].…”

“…However, the maximum contamination level set by the U.S. EPA and China for total concentration of four regulated THMs is 80 g/L in drinking water. I-THM concentrations are generally 100-1000 times lower than those of regulated THMs [17]. The DVB/CAR/PDMS was therefore selected as the fiber; this represents a compromise between the smaller and the heavier THMs, and allows for the simultaneous analysis of I-THM species, partly because the fiber is a mix of mesopores and micropores.…”

“…Increasing the temperature during the adsorption period increased the extraction rate for higher molecular weight compounds but also had the adverse effect of decreasing the sensitivity for smaller compounds. An extraction temperature of 70 • C was selected to maximize the response of the larger molecular weight I-THMs [17], and 40 • C was selected for SPME of HANs [10]. However, the water vapor condensation on the fiber was observed at 70 • C which could be harmful to GC-MS.…”

“…The DVB/CAR/PDMS fiber was found to be more suitable for the range of analytes, and the novel PDMS/DVB-NVP fiber for brominated acetonitriles [14]. The six Iodo-THMs from drinking water were extracted using SPME and the carbowax/divinylbenzene (carbowax/DVB) fiber [16,17]; this analysis had similar precision to LLE methods for the analysis of Iodo-THMs [1,4]. Based on the developed method [17], six target Iodo-THMs at low levels were analyzed in iodine-containing waters by ozone treatment to obtain information on I-THM formation processes and factors influencing the safety of drinking water [18].…”