[A novel ship-borne positive pressure solid phase extraction device to enrich organo chlorinated and pyrethroid pesticides in seawater].

A novel solid phase extraction (SPE) device driven by positive pressure was developed instead of negative pressure from a vacuum pump, in order to enrich organo chlorinated and pyrethroid pesticides in seawater. The water sampling bottles and the pipelines which touch water samples were made of plastic material without chlorine. In order to ensure the sealing and firmness, the whole device were tightened with nut and bolt. The inner pressure (0.1-0.3 MPa) in the water sampling bottle was provided by the small air pump (powered by 12 V cell) controlled by a microprogrammed control unit (MCU) and pressure sensor to keep the water flow rate (4.0-6.0 mL/min). The pre-conditioned SPE column can be used for the enrichment of pesticides within four weeks, and the loaded SPE column can be eluted for detection within six weeks with recoveries greater than 80%. The linearity of the method was good with the correlation coefficient more than 0.9. The limits of quantification (LOQs) were 0.8-6 ng/L. The recoveries of the pesticides at three spiked levels (3 parallel samples) were 86.1%-95.5% with the relative standard deviations less than 10%. The benzene hexachlorides (BHCs) and dichloro-diphenyl-trichloroethanes (DDTs) were detected in seawater samples. The device has good application in enriching organo chlorinated and pyrethroid pesticides in seawater.

[Determination of buprofezin, methamidophos, acephate, and triazophos residues in Chinese tea samples by gas chromatography].

A method has been developed for the simultaneous determination of buprofezin, methamidophos, acephate and triazophos residues in Chinese tea samples. The pesticide residues were extracted from tea samples with a mixture of ethyl acetate and n-hexane (50:50, v/v) at 45 degrees C. The extracts were subsequently treated with a column packed with 40 mg of active carbon by gradient elution with ethyl acetate and n-hexane. Buprofenzin and the three organophosphorus pesticides were analyzed by gas chromatography using a DB-210 capillary column and a nitrogen-phosphorus detector. The recoveries for spiked standards were 73.4%-96.9%. The relative standard deviations were all within 4.63%. The limits of quantitation (3sigma) in the tea samples were about 7.0-12.0 microg/kg.