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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.

A method is formulated to model the properties of honeycomb paperboard based on Hilbert transform, In this method, there are no assumptions on the forms of the stiffness and damping properties, this method is truly nonparametric. An experiment system is set up to record the free response of the mass loaded honeycomb paperboard system, the experiment data are used to identify the stiffness and damping properties of honeycomb paperboard. The motion equation of mass loaded honeycomb paperboard system is formulated, the transmissibility curve is simulated, the comparison of the simulated curves and the experiment data indicates the model in this paper is accurate.