An investigation in the use of solid phase microextraction gas chromatography-mass spectroscopy (SPME-GC/MS) for the analysis of THMS from water samples

Barter, David M. (2014) An investigation in the use of solid phase microextraction gas chromatography-mass spectroscopy (SPME-GC/MS) for the analysis of THMS from water samples. Memorial University of Newfoundland. (Unpublished)

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Abstract

Difficulties in sample preservation for semi volatile samples, like trihalomethanes (THMs) in water, often limit the extent of water analyses that may be undertaken to assess a particular water body. Analysis techniques such as liquid-liquid extraction and purge and trap followed by ion exchange (IE) or by high performance liquid chromatography (HPLC) that are currently used only just meet analysis regulatory requirements. Hence, other techniques and their method development are needed to quicken the sampling, extraction and analysis process times. A potential method that may hold promise is the use of head-space solid-phase microextraction (HS-SPME) sampling combines with gas chromatography-mass spectrometry (GC/MS) separation and detection methods. This work has investigated this technique and a method has been developed to assess concentrations of trihalomethanes (THMs) and their derivatives from natural sources of drinking water that are used for the municipality of the Corner Brook, Newfoundland area. Under laboratory conditions, surrogate THM standard samples to include: bromodichloromethane (CHCl2Br), chlorodibromomethane (CHClBr2), chloroform (CHCl3), 1,2-dibromoethane (C2H4Br2), and 1,2-dichloroethane (C2H4Cl2) of known concentrations (200, 100, 50, 25, 10, 5, 2, and 1 ppm to cover the required analysis range) in methanol samples were analyzed in stirred and sealed vials using head space (HS-SPME) sampling. This was undertaken to fully optimize all sampling and extraction condition parameters, which included (found optimized parameters): choice of type of extraction fiber used (PDMS/DVB), stirring rate of samples (900rpm), extraction temperature of the sample (25oC), extraction time required (4 min), desorption time of the fiber in the GC injector port for analysis (2 min), and the determination of maximum averaged equilibrium conditions for a number of THM analytes (4 min). Further, an optimized temperature profile for separation by GC for the analysis of this set of the THMs was found to be: 30oC held for 5 minutes, followed by a ramp of 5oC/min to 50oC to give a total run time of 9 minutes, when the GC injector port was set at 250oC, GC transfer line to the MS was 240oC and the MS source was held at 200oC. Under the determined optimized conditions water samples were taken from natural waters and analysed for their THM concentrations. Concentrations in the natural water samples were measured at a range of 254 ppb-4.42ppm with good detection limits (<1ppm) and linear working range(10-1 ppm) of the calibration data. RSDs for SPME extraction averaged between 4.17 and 11.6% for each THM component.

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