Optimization of Ultrasonic Extraction and Clean-up Protocol for the Determination of Polycyclic Aromatic Hydrocarbons in Marine Sediments by High-performance Liquid Chroma-tography Coupled with Fluorescence Detection

The procedures of ultrasonic extraction and clean-up were optimized for the determination of polycyclic aromatic hydrocarbons (PAHs) in marine sediments. Samples were ultrasonically extracted, and the extracts were purified with a miniaturized silica gel chromatographic column and analyzed with high performance liquid chromatography (HPLC) with a fluorescence detector. Ultrasonication with methanol-dichloromethane (2:1, v/v) mixture gave higher extraction efficiency than that with dichloromethane. Among the three elution solvents used in clean-up step, dichloromethane-hexane (2:3, v/v) mixture was the most satisfactory. Under the optimized conditions, the recoveries in the range of 54.82% to 94.70% with RSDs of 3.02% to 23.22% for a spiked blank, and in the range of 61.20% to 127.08% with RSDs of 7.61% to 26.93% for a spiked matrix, were obtained for the 15 PAHs studied, while the recoveries for a NIST standard reference SRM 1941b were in the range of 50.79% to 83.78% with RSDs of 5.24% to 21.38%. The detection limits were between 0.75 ng L-1 and 10.99 ng L-1for different PAHs. A sample from the Jiaozhou Bay area was examined to test the established methods.

Determination and Prediction of Binary Solubility for Aromatic-Tetraethylene Glycol (with Water) Systems

The binary solubilities of tetraethylene glycol (TTEG) with benzene, toluene or p xylene, were measured by the turbidity point method. In TTEG the content of water ranged from 0 to 5% and the test temperature ranged from 20℃ to 120℃. Increasing the temperature resulted in greater solubility of the aromatics in TTEG, while increasing the content of water caused the aromatic solubility to decrease. The benzene solubillity in TTEG was the greatest followed by toluene and xylene at the same water content and temperature. The mutual solubility was predicted by correlating the paramaters of a new group for the UNIFAC model for the aromatics extraction system. The modified UNIFAC group contribution model was used to predict the binary solubility of TTEG and aromatics. The average deviation between the experimental result and prediction is 4.06%. Therefore, the UNIFAC model can be used to describe the solubility phenomena for TTEG aromatics systems.

A novel method through solid phase extraction combined with gradient elution for concentration and separation of 66(ultra)trace persistent toxic pollutants in Antarctic waters

This study developed a method to perform the simultaneous concentration and selective separation of 66 （ultra） trace persistent toxic substances in Antarctic waters. The substances included 30 polychlorinated biphenyls, 17 organochlorine pesticides, 16 polycyclic aromatic hydrocarbons, 3 hexabromocyclododecanes. Solid phase extraction was performed using a C18 membrane and silica gel column. Gradient elution was conducted using organic solvents with different polarities; as a result, the efficiency of the C18 film is improved and the interferences from impurities and target compounds are eliminated. Extracts were subsequently analyzed through gas chromatography or liquid and gas chromatography coupled to tandem mass spectrometry. Method validation yielded the following values： recoveries of all target analytes in the Antarctic water ranged from 87.3% to 117.6% and reproducibility as percent relative standard deviation was lower than 5%. Quantification limits ranged from 0.004 μg L^-1 to 0.030 μg L^-1. The established method improved the recoveries and reduced the limits of detection. Results indicated the method exhibited good performance in the simultaneous concentration and selective separation of 66 （ultra） trace organic pollutants; Therefore, the proposed sample pretreatment can potentially eliminate the effects of various classes of impurities to some extent.