Analytical & Bioanalytical Techniques

Biography

Biography: Yuhui (Henry) Zhao

Abstract

Monitoring volatile organic compounds (VOC) and Disinfection-by-Product such as Trihalomethanes (THM) in water samples, is one of the major tasks routinely carried out in our laboratory. Due to its low cost, simplicity, high sensitivity and wide linear range to non-chloranated organic compounds, gas chromatograph with an flame ionization detector (GC-FID) is always our first choice of instruments. However, FID has its own limitations. The low sensitivity of FID to multi-chloranated VOCs may not satisfy the low detectiom limit requirment. In some cases, these compounds need to be analyzed on a more senstive (but specific) detector, such as an Electron Capture Detector (ECD). Further, FID respond to any carbon-contaning organic componds, and can not distinguish those co-eluted. Co-eluted compounds are often re-analyzed on a different instrument (or detector ) for confirmation. A significant amount of time and effort was spent on these repeated analysis. To overcome these difficulties, we used a one-injector, one–column and dual-detector (FID and ECD) configuration. Sample injected through the inlet, separated by a capilary column, and the effluent is splited into two streams. The major stream with over 95% of the flow directed to the FID, and the minor stream with less than 5% of flow directed to an ECD. Thus, with a single run, two sets of data are obtained simultaneously. A macro-program was developed in-house to do the data handling. The program compare the two sets of data and make judgement on compound identification. Some of the wrongly identified compound results are automatically converted to the right value. This eliminated the necessity of using a second set of analytical instruments, or switching the column back and forth between detectors. With this practice, not only time and effort are saved, but also the certainty in data quality is significantly increased.