Michel Montury

Solid-phase microextraction coupled with high performance liquid chromatography: a complementary technique to solid-phase microextraction-gas chromatography for the analysis of pesticide residues in strawberries.

Solid-phase microextraction coupled with high performance liquid chromatography has been studied for the analysis of methiocarb, napropamide, fenoxycarb and bupirimate in strawberries. The strawberries were blended and centrifuged. Then, an aliquot of the resulting extracting solution was subjected to solidphase microextraction (SPME) on a 60 μm polydimethylsiloxane /divinylbenzen e (PDMS/DVB) fibre for 45 min at room temperature. The extracted pesticides on the SPME fibre were desorbed into SPME/ high performance liquid chromatography (HPLC) interface for HPLC analysis with diode-array detection (DAD). The method is organic solvent-free for the whole extraction process and is simple and easy to manipulate. The detection limits were shown to be at low μg kg−1 level and the linear response covered the range from 0.05 to 2 mg kg−1 of pesticides in strawberries with a regression coefficient larger than 0.99. A good repeatability with RSDs between 2.92 and 9.25% was obtained, depending on compounds.

Sampling atmospheric pesticides with SPME: laboratory developments and field study.

To estimate the atmospheric exposure of the greenhouse workers to pesticides, solid phase microextraction (SPME) was used under non-equilibrium conditions. Using Ficks law of diffusion, the concentrations of pesticides in the greenhouse can be calculated using pre-determined sampling rates (SRs). Thus the sampling rates (SRs) of two modes of SPME in the lab and in the field were determined and compared. The SRs for six pesticides in the lab were 20.4-48.3 mL min(-1) for the exposed fiber and 0.166-0.929 mL min(-1) for the retracted fiber. In field sampling, two pesticides, dichlorvos and cyprodinil were detected with exposed SPME. SR with exposed SPME for dichlorvos in the field (32.4 mL min(-1)) was consistent with that in the lab (34.5 mL min(-1)). SR for dichlorvos in the field (32.4 mL min(-1)) was consistent with that in the lab (34.5 mL min(-1)). The trends of temporal concentration and the inhalation exposure were also obtained.

Microwave/SPME method to quantify pesticide residues in tomato fruits

A new analytical method using focused microwave-assisted extraction (FMAE), coupled with solid phase micro-extraction (SPME), has been elaborated to determine 25 pesticides used in tomato cultivation. Microwave energy was used for a fast and controlled heating of solvent to selectively extract compounds. Calibration curves were plotted from blank tomato samples spiked at different concentrations with standards. A linear response was obtained between 10 and 1000 μ g/Kg for pyrethroids and between 0.1 and 5000 μ g/Kg for other compounds. For all studied substances, the resulting correlation coefficient (r2) was greater than 0.99. Limits of detection (LOD) and quantification (LOQ) were measured lower than 8 and 25 μ g/Kg, respectively. The relative standard deviation (RSD) was determined below 15% for all pesticides. Field incurred tomato samples were used to validate the new FMAE/SPME method. Observed analysis results by using this technique were in good agreement compared to those obtained by two accredited trading laboratories using traditional methods. Four tomato samples, bought in a local market, were also tested with the FMAE/SPME method.

Flexibility of solid-phase microextraction for passive sampling of atmospheric pesticides.

For low volatile pesticides, the applications of solid-phase microextraction (SPME) as an air sampler were reported with sampling time chosen in the linear stage of the sorption kinetics because of long equilibrium time. In these pre-equilibrium conditions, sampling rates (SRs) expressed as the volume of air sampled by the SPME sampler per unit of time, were used to estimate analytes concentrations in air. In the present study, to achieve good extraction performance and accurate calibration, the sorption kinetics of several pesticides with SPME were investigated in detail, with a focus on parameters influencing SRs. Linear air velocity was found to be the main parameter affecting SRs. For exposed fibers, with air velocities below 20-25 cms(-1), SRs increased with increasing air velocity. When linear air velocity was equal to or greater than 25-30 cms(-1), it had little effect on SRs. To improve the flexibility of SPME, different configurations of SPME were compared, i.e. different lengths of fibers exposed, retracted fibers, exposed fibers with grids. SRs were linearly proportional to exposed lengths of fibers. Using grids, lower SRs and wider calibration time range were achieved. SRs for retracted fibers were the lowest among the different experimented configurations. The accuracy of calibration was improved and more flexibility of SPME was provided.

Pesticide vapours in confined atmospheres. Determination of dichlorvos by SPME-GC-MS at the µg m−3 level

A method based on SPME is described for assessing the gaseous dichlorvos concentration in confined atmospheres like a greenhouse after a pesticide application. Sampling was made by using SPME with PDMS fibres immersed into a 250 mL sampling flask into which air samples were dynamically pumped from the analysed atmosphere. Sampling duration was 40 min and samples were then analysed by GC-MS. Calibration was performed from a vapour saturated air sample and gas phase diluted samples, and this procedure afforded a curve with a regression coefficient (R2) higher than 0.98. The repeatability of these measurements was observed with an RSD of 2.5%. This analysis procedure was then applied for the determination of gaseous dichlorvos concentrations versus time, in the atmosphere of an experimental 8 m2 and 20 m3 greenhouse. The pesticide was sprayed according to real cultivation conditions and measurements were made from 2 up to 74 h after application affording observed concentrations in the range of decades and hundreds of microg m(-3) (corresponding limits of detection and quantification were found at the level of a few microg m(-3)).

Stabilisation of fatty duck liver by high pressure treatment

Abstract The well known product foie gras, fatty goose or duck liver, is a traditional French product of high organoleptic value, and can be processed through different ways: fresh, it should be used immediately (restaurants); “half cooked”, it should be kept refrigerated up to 42 days (depending of temperature reached at coldest point). Pasteurisation with complete cooking allows a shelf life up to 6 months at + 4°C. Thennal sterilisation is also possible for room temperature storage, but the process is ddlicult to handle and the given Fo values are kept low. The fatty liver is highly fragile and all thermal processing lead to a certain extent of fat melting and browning, detrimental to the yield and to the organoleptic properties.

Stabilization of black truffle of Perigord (Tuber melanosporum) by high pressure treatment.

Abstract The effects of combined high pressure (550 MPa for 30 min) and low temperature (40°C, 60°C and 80°C) treatments on the microbial contamination and organoleptic qualities (aroma, taste and exudation) of black truffle samples were compared with those of classical thermal sterilization (100°C for 3 hours). All the high pressure treatments at 40°C, 60°C and 80°C, caused a fungi flora inactivation and drastic reductions of the total mesophilic contamination which turns from 107 to 102 or to less than 10 CFU/g. The exudat ratio, as well as aroma, seems to present no significant change between pressurized samples and sterilized ones. Described pressure treatments at low temperature followed by storage at 4°C, afford a method for microbial stabilization of black truffles.