Single drop microextraction and gas chromatography-mass spectrometry for the determination of diflufenican, mepanipyrim, fipronil, and pretilachlor in water samples.

An analytical method for the determination of diflufenican, mepanipyrim, pretilachlor, and fipronil in water samples was developed using single drop microextraction in the direct immersion mode and gas chromatography-mass spectrometry. A factorial fractionated design of type 2(6-1) at two levels was performed, to study the influence of experimental variables such as ionic strength, pH, agitation speed, extraction time, drop volume, and sample volume. To establish the optimal conditions for the variables that were significant, a Doehlert design was performed. The optimum conditions of extraction were 1 µL of heptane immersed in 4.0 mL of sample with continuous agitation at 500 rpm for 30 min at room temperature. The developed method proved to have good linearity for the range studied. The detection limits were 0.07 µg L(-1) for diflufenican, 0.03 µg L(-1) for mepanipyrim, 0.08 µg L(-1) for pretilachlor, and 1.39 µg L(-1) for fipronil. The method was validated on river water samples, showing the absence of matrix effect and recoveries ranged from 90.1 to 107.8 %. The results show that the method developed is accurate, sensitive, rapid, simple, and low cost, so it is recommended for application in the analysis of these different classes of pesticides in water samples.

Determination of anti-inflammatory drugs in water samples, by in situ derivatization, solid phase microextraction and gas chromatography-mass spectrometry.

A new analytical method for the determination of non-steroidal acidic anti-inflammatory drugs in water samples is described. These compounds are used as anti-inflammatory, antipyretic and analgesic drugs in human health care and in veterinary applications. Analytical procedure involves in situ derivatization of analytes to their methyl esters with dimethyl sulphate, headspace sampling using solid-phase microextraction (SPME), and gas chromatography-mass spectrometry (GC-MS). The effects of pH, ionic strength, extraction time, SPME fibre, extraction temperature as well as derivatization conditions were studied. Methyl esters were extracted with a fused-silica fibre coated with 100 microm polydimethylsiloxane. Response was linearly dependent on concentration in the range 0.1-10.0 ng mL(-1). Detection limits were achieved at the level of 0.3-2.9 ng L(-1). Derivatization-SPME/GC-MS analysis yielded good precision (R.S.D. between 7.9 and 17.2%). The method was validated by analysis of spiked matrix samples.