1. Determination of Trihalomethane Concentrations in Drinking Water using Membrane-based GC-MS
Water chlorination is an effective process for preventing water borne diseases, yet forms halogenated disinfection by-products (DBPs) from the reaction of natural organic matter with free available chlorine.[1, 2] The two main classes of DBPs are the trihalomethanes (THMs) and the haloacetic acids (HAAs). These compounds are considered to be possible carcinogens, so are regulated by the USEPA in finished drinking water. Current methods of analysis for THMs work well, but often require organic solvents or expensive sampling systems to perform. The main goal of this project is to use an alternative, solvent free membrane-based gas chromatography-mass spectrometry (GC-MS) method to determine THM concentrations in drinking water samples. The membrane sampling device[3, 4] employed in this research is comprised of two stainless steel tee unions and a Tefzel® tubing shell with polymeric membrane tubing inserted inside. When drinking water flows through the device, volatile compounds in the water permeate through the membrane walls and into an inert gas stream. The enriched gas stream is then analyzed by a GC-MS instrument (Figure 1).[4]
Figure 1. Membrane sampling device interfaced to a GC-MS instrument.
The student researcher(s) working on this project will conduct a literature survey, gain experience using a GC-MS instrument; learn to optimize method parameters and conditions, perform calibration studies (e.g. external and internal standard), conduct matrix spiking studies, and apply the method to the analysis of drinking water samples from New York State.
[1] Rook, J. J. (1974). Water Treatment and Examination, 23, 234–243.
[2] Krasner, S. W., Weinberg, H. S., Richardson, S. D., Pastor, S. J., Chinn, R., Sclimenti, M. J., Onstad, G. D., & Thruston Jr., A. D. (2006). Environmental Science and Technology, 40(23), 7175-7185.
[3] Brown, M. A. & Emmert, G. L. (2006). Analytica Chimica Acta, 555, 75-83.
[4] Emmert, G. L., Brown, M. A., Geme, G., Simone, P., Cao, G. (2007). Project 2873, Awwa Research Foundation.
2. Evaluation of Polymeric Membranes for the Extraction of Volatile Compounds from Drinking Water
Polymeric membranes can be used for a variety of applications including gas and liquid extraction, recovery and purification of organic solvents, and sample introduction for analytical instrumentation. The extraction of volatile, non-polar compounds from a liquid or air matrix is governed by the concentration gradient that exists between the membrane-matrix interfaces. Two main processes are involved in the permeation process. (1) Convection resulting in mass flow in the axial direction and (2) Diffusion resulting in mass flow in the radial direction with respect to tubing walls.[1, 2, 3] For analytical purposes, steady state conditions (Fick's first law) should be satisfied as fast as possible to reduce sampling times. The main goal of this project is to evaluate various polymeric membranes for the extraction of volatile compounds from drinking water. A membrane, which can rapidly, selectively, and reproducibly extract analytes is desired.
The student researcher(s) working on this project will conduct a literature survey, evaluate both non-porous and porous membranes, gain experience using a membrane introduction flame ionization detection system, and learn to use mathematical modeling software.
[1] Sysoev, A. A. (2000). Analytical Chemistry, 72, 4221-4229.
[2] LaPack, M. A., Tou, J. C., & Enke, C. G. (1990). Analytical Chemistry, 62, 1265-1271.
[3] Boscaini, E., Alexander, M. L., Prazeller, P., Märk, T. D. (2004), International Journal of Mass Spectrometry. 239, 179-186.
