Determination of Trace PCB in Water by GC-MS with Ionic Liquid Based Headspace Single-Drop Microextraction under Ultrasound

An accurate and sensitive method has been developed for the determination of PCBs in water by gas chromatography coupled with mass spectrometry (GC/MS) with ionic liquid based headspace single-drop microextraction under ultrasound. The sample injection part of gas chromatographic instrument was modifed to avoid the ionic liquid leaking, selected 1-butyl-3-methylimidazolium hexafluorophosphate ([C4MI[PF6]) as extracting agents. Experimental parameters influencing the extraction performance, such as desorption temperature, ultrasound extraction time, extraction temperature, ionic liquid headspace volume and salt effect, were optimized. Calibration curve was linear within the range of 10~300.0 μg/L, and the extraction recoveries with RSD values lower than 9.1% were from 77.6% to 103.3%. The limits of detections (LOD), calculated on the basis of signal-to-noise ratio of 3 (S/N=3), was in the range of 0.005~0.007 μg/L. This method is found to be simple, sensitive, little interferential and good specificity for the determination of trace PCBs in water. Real sea sample was successfully analyzed using this method.

New Approach to Processing of Gas Chromatographic/Mass Spectrometric Data for Detection of Off Flavors in Complex Mixtures

Chemical compounds responsible for off flavors in foodstuffs are often difficult to identify because of their low levels in complex matrixes. A simple method is described to detect and identify off flavor compounds by gas chromatographic/mass spectrometric (GC/MS) analysis and data processing for sorting the GC/MS files in 14-ion series. The 14 homologous-ion series correspond to the sum of the intensities of the ions, x + (CH2)n, where x varies from 1 to 14 and n varies from 1 to ∞, allowing to cover the whole acquired mass range. Processing of the ion series allows automatic screening of all acquired masses. We use this method routinely in our laboratory to find compounds responsible for a contamination. It is a powerful tool for off flavor identification by comparison between a reference and a contaminated sample. The method can be used with any type of data system and any chromatographic instrument coupled to a mass spectrometer.