Headspace gas chromatograph

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Gas chromatograph (GC) allows qualitative and quantitative determination of volatile fatty acids (VFA) i.e. short-chain organic acids which are important intermediates in biological wastewater treatment processes such as anaerobic digestion, phosphorus removal and denitrification. VFA measurement is required to monitor these processes in our laboratory. Due to the complex matrix wastewater or sludge, the samples usually require a series of pretreatment processes such as acidification, centrifuge, filtration, distillation, derivatisation and extraction etc. prior to GC analysis, which is not only time consuming (about 2 hours per sample), but also costly in terms of solvent purchase and waste disposal. We analyze dozens of samples per day from our ongoing anaerobic digestion of manure and sludge, phosphorus removal and denitrification projects and can ill afford a lengthy sample preparation procedure. We are presently using direct sample injection following simple filtration. As a result, the GC injector and column systems are exposed to the dissolved contaminants in samples and require daily cleanup and frequent replacement of accessories such as column and insert liner etc. These extensive instrumental services not only reduce the sample throughput, but again are expensive. Headspace GC can avoid these problems and offer relatively rapid and solvent-free analyses through online sample preparation. In the headspace GC, VFA is first converted into gas phase and then introduced into GC, the contaminants in liquid are left behind with minimization of interferences. Our existing GC system is designed primarily for analysis of the permanent gases and it has limited capacity for liquid samples such as VFA in wastewater. Analyzing samples using headspace in the other university labs requires weeks and cannot be relied on for most of daily research scenarios, especially for dynamic studies. In summary, our present GC is struggling with contamination from the dirty wastewater or sludge samples and only a new headspace GC can solve the problem leading to effective delivery of our grant work.