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MEMBRANE EXTRACTION GC/MS FOR THE ANALYSIS OF DISINFECTION BY-PRODUCTS
Citation:
Shoemaker, J A. MEMBRANE EXTRACTION GC/MS FOR THE ANALYSIS OF DISINFECTION BY-PRODUCTS. Presented at ILSI Workshop on Identification of New and Uncharacterized Disinfection By-Products in Drinking Water, Washington, DC, February 10-13, 1998.
Description:
For many years, public water supplies in the U.S.have been treated with a variety of chemicals aimed at reducing or eliminating infectious diseases. Chlorine is the most common disinfectant used to combat waterborne microbial diseases; however, the use of ozone, chlorine dioxide, and chloramine as disinfectants is on the rise. While reducing the microbial risk, the use of disinfectants poses potential health risks due to disinfectoin by-products (DBPs) formed during the water treatment. The most common analytical techniques employed to characterize DBPs in water are purge and trap analysis and liquid-liquid or liquid-solid extraction followed by gas chromatrography/mass spectrometry GC/MS) analysis. These techniques are suitable for detecting purgeable DBPs and less water soluble, nonpolar semivolatile DBPs. However, the hydrophilic fraction of drinking water typically does not purge from water samples or breaks through typical solid-phase sorbents. Therefore, it is the goal of this research to evaluate the ability of on-line, semipermeable membranes, followed by GC/MS analysis, to extract polar, water soluble DBPs from drinking water.
While many membrane designs are being developed, most designs do not involve any type of separation. The membrane design presented here is in-line with a gas chromatograph which will allow separation of the analytes permeating the membrane. A membrane extraction module has been designed which houses a capillary Silastic membrane (0.025" i.d. x 0.047" o.d.). The water sample flows through the capillary membrane fiber and analytes permeating through the membrane will be swept by helium into the glass liner of a Varian 3400 GC injection port. The GC injection port and capillary column are held at subambient temperatures during the time (typically 10 min) the sample is flowing across the membrane. The injection port is then heated rapidly to 250 degrees C while the capillary column is still at subambient temperatures. Once the injection port reaches 250 degrees C, the capillary column is ramped to chromatographically separate the analytes and detection is achieved with a Finnigan MAT TSQ 700 triple quadrupole mass spectrometer.
The new membrane design will be evaluated on a model set of hydrophilic compounds. The selected compounds, listed below, are not necessarily DBPs, however they are polar and water soluble which make them very difficult to extract with conventional methods: butanal, propargyl alcohol, 2-methyl-1-propanol, pyridine, 1,1-dichloracetone, chloroacetronitrile, N-nitrosodimethylamine, N,N-dimethylformamide, 1,3-dichloro-2-propanol, aniline, and phenol. Initial research on the new design and its applicability to hydrophilic compounds will be presented.