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PubMed2004

New trends in sample preparation: on-line microextraction in packed syringe (MEPS) for LC and GC applications Part III: Determination and validation of local anaesthetics in human plasma samples using a cation-exchange sorbent, and MEPS-LC-MS-MS.

The need for on-line sample preparation for high-throughput applications in bioanalysis has increased during the past decade. In this paper a robust and on-line sample preparation technique, micro extraction in packed syringe (MEPS) has been developed and validated. The method is a miniaturized, fully automated, solid-phase extraction (SPE) technique that can be connected on-line to GC or LC without any modification of the chromatographs. The performance of MEPS as sample preparation method is illustrated by the determination of local anaesthetics in human plasma samples on-line with high performance liquid chromatography (HPLC) and tandem mass spectrometry. The sampling sorbent was 1mg silica based benzenesulphonic acid cation exchanger that was inserted in a 250 microl syringe. Ropicavine and two of its metabolites (PPX and 3-OH-ropivacine), lidocaine and bupivacine were used as model substances. The accuracy values of quality control samples (QC) were between 95% and 109%, and precision (relative standard deviation, R.S.D.) had a maximum deviation of 9% for the analytes.

Anesthetics↗
PubMed2026

Evaluation of the effects of domestic tomato processing on biopesticide residue using natural deep eutectic solvents (NADES) extractions.

The present study evaluated the fate of fourteen botanical biopesticides in processed tomato samples. Various processing methods were employed, including washing, dehydration, and the preparation of juice and sauce. The extraction was performed using more sustainable techniques, aimed at minimizing the environmental impact of conventional organic solvents by substituting them with natural deep eutectic solvents (NADES). Solid-liquid extraction (SLE) and dispersive liquid-liquid microextraction with solidification of floating organic drop (DLLME-SFOD) were utilized for solid and liquid tomato samples, respectively. The NADES used was choline chloride:2,3-butanediol (ChClBt) at a 1:4 molar ratio for both techniques, resulting in recovery values ranging from 69.2 to 106.2% for SLE, and extraction efficiencies reaching up to 46.2% for DLLME-SFOD. The impact of these processes was evaluated employing the processing factor (PF), yielding PF values of less than 1 in all cases. Compounds as pyrethrins, azadirachtin, and rotenone persisted after processing, posing a potential consumer risk.

Solanum lycopersicum↗
PubMed2006

Funnelform single-drop microextraction for gas chromatography-electron-capture detection.

A funnelform single-drop microextraction was developed for gas chromatography-electron-capture detection. A solvent microdrop of 4 microL was formed at the tip of a microsyringe needle assembled with a small brass funnel in the microextraction. In the funnel, the restricted microdrop was shaken gently by circular motion in an aqueous sample solution. Eleven organochlorine and two pyrethroid pesticides were used as the model compounds for evaluating the microextraction. The parameters affecting the enrichment factor of the microextraction were investigated, including the funnel inner angle, solvent component, and microdrop volume, etc. With the optimized microextracting conditions, the enrichment factors of organochlorines and pyrethroids were 272-875 and 147-183, respectively. The detection limit was in the range of 1-12 ng/L (S/N = 3). The relative standard deviation (RSD) of peak height was less than 10.2% (n = 8). This proposed technique is simple, convenient, and efficient.

Chromatography, Gas↗
PubMed2006

Direct determination of chlorophenols in environmental water samples by hollow fiber supported ionic liquid membrane extraction coupled with high-performance liquid chromatography.

The 1-octyl-3-methylimidazolium hexafluorophosphate ([C8MIM][PF6]) ionic liquid was immobilized in the pores of a polypropylene hollow fiber for hollow fiber-protected liquid-phase microextraction. Analytes including 4-chlorophenol (4-CP), 3-chorophenol (3-CP), 2,4-dichlorophenol (2,4-DCP) and 2,4,6-trichlorophenol (2,4,6-TCP) were extracted into this ionic liquid membrane, and back extracted into 10microL sodium hydroxide acceptor solution in the lumen of the hollow fiber. Then, the acceptor solution was withdrawn into the high-performance liquid chromatography (HPLC) microsyringe connected to the hollow fiber, and directly injected into the HPLC system for analysis. Some parameters that might affect the extraction efficiency were optimized, and low detection limits (0.5microgL(-1) for 4-CP, 3-CP, DCP and 1.0microgL(-1) for TCP) were obtained. Good repeatability was achieved because of the stability of the hollow fiber-supported ionic liquid membrane. The proposed procedure was applied for direct determination of the four chlorophenols in some real water samples including groundwater, river water, wastewater and tap water. All of the four chlorophenols in these water samples were under the limits of determination, and the recoveries were in the range of 70.0-95.7% at 5microgL(-1) spiked level.

Chlorophenols↗
PubMed2000

Preliminary studies of a fast screening method for polycyclic aromatic hydrocarbons in soil by using solvent microextraction-gas chromatography.

Solvent microextraction (SME) was applied to the extraction of polycyclic aromatic hydrocarbons (PAHs) from spiked and real environmental soil samples with different matrices. Soil sample was mixed with 7 mL of acetone and 14 mL of water to allow partitioning of the PAHs from the soil to the liquid phase. A 2 microL octane drop suspended from a microsyringe needle tip was then immersed into the stirred solution-soil mixture for extraction. After an 11 min extraction, the octane drop was withdrawn into the syringe and injected directly into the GC for identification and quantification. The whole analysis procedure took 27 min, with an extraction time of 11 min, and a GC separation time of 16 min. A second extraction could be undertaken whilst the GC is running, hence the GC run time currently limits the sample throughput. In this method, a small amount of organic solvent was used for the extraction process, which produced little waste. The limits of detection for lower molecular weight (< 230) PAHs range from 0.13 to 0.36 mg kg-1, and for higher molecular weight (> 250) PAHs are estimated to be between 0.5 and 1.0 mg kg-1, with RSD values generally under 20%. Due to the small volumes of organic solvent used, the consumable cost per extraction is only US$ 0.12. This is the first report of the application of SME to solid samples, and the first report of the use of SME for the analysis of PAHs.

Acetone↗