TSF experiment for comparison of high Reynolds number turbulence in both HeI and HeII: First results

International audienceTSF experiment for comparison of high Reynolds number turbulence in both HeI and HeII: First result

A Workflow for Multiclass Determination of 256 Pesticides in Essential Oils by Liquid Chromatography Tandem Mass Spectrometry using Evaporation and Dilution Approaches: Application to Lavandin, Lemon and Cypress Essential Oils

International audienceThis paper describes the determination of 256 multiclass pesticides in cypress and lemon essential oils (EOs) by the way of liquid chromatography–electrospray ionization tandem mass spectrometry (LC-ESI/MS/MS) analysis using the scheduled selected reaction monitoring mode (sSRM) available on a hybrid quadrupole linear ion trap (QLIT) mass spectrometer. The performance of a sample preparation of lemon and cypress EOs based on dilution or evaporation under nitrogen assisted by a controlled heating were assessed. The best limits of quantification (LOQs) were achieved with the evaporation under nitrogen method giving LOQs≤10 µg L−1 for 91% of the pesticides. In addition the very satisfactory results obtained for recovery, repeatability and linearity showed that for EOs of relatively low evaporation temperature, a sample preparation based on evaporation under nitrogen is well adapted and preferable to dilution. By compiling these results with those previously published by some of us on lavandin EO, we proposed a workflow dedicated to multiresidue determination of pesticides in various EOs by LC-ESI/sSRM. Among the steps involved in this worflow, the protocol related to mass spectrometry propose an alternative confirmation method to the classical SRM ratio criteria based on a sSRM survey scan followed by an information-dependent acquisition using the sensitive enhanced product ion (EPI) scan to generate MS/MS spectra then compared to a reference. The submitted workflow was applied to the case of lemon EOs samples highlighting for the first time the simultaneous detection of 20 multiclass pesticides in one EO. Some pesticides showed very high concentration levels with amounts greatly exceeding the mg L−1

Influence of complexation phenomena with multivalent cations on the analysis of glyphosate and aminomethyl phosphonic acid in water.

Article de revue (Article scientifique dans une revue à comité de lecture)International audienceExperimental and theoretical influence of multivalent cations on the analysis of glyphosate and aminomethyl phosphonic acid (AMPA) was studied in pure water and in one surface water. The procedure chosen, based on derivatization with FMOC-Cl, HPLC separation, and fluorescence detection, appears highly affected at cations concentrations current in natural waters. A detailed speciation study performed with the VMINTEQ software strongly suggests that the complexes formed between analytes and cations do not dissociate during the reaction and do not react with the derivatization agent, so that only the free forms are derivatized. These results point out the necessity of a pre-treatment to prevent these interferences, even in low salinity waters. The different ways conceivable are discussed in terms of kinetic and thermodynamic considerations.</p

Advantages of the scheduled selected reaction monitoring algorithm in liquid chromatography/ electrospray ionization tandem mass spectrometry multi-residue analysis of 242 pesticides: a comparative approach with classical selected reaction monitoring mode

International audienceThis paper illustrates the advantages of using the scheduled selected reaction monitoring (sSRM) algorithm available in Analyst1 Software 1.5 to build SRM acquisition methods in the application field of pesticide multi-residue analysis. The principle is to monitor the SRM transitions only when necessary. Based on the analytes’ retention times, the scheduled SRM algorithm decreases the number of concurrent SRM transitions monitored at any point in time, allowing both cycle time and dwell time to remain optimal at higher levels of SRM multiplexing. To compare the scheduled SRM and the classical SRM modes, a mixture containing 242 multi-class pesticides has been analyzed ten times by three acquisition methods, using liquid chromatography/tandem mass spectrometry (LC/MS/MS) with an API 4000 QTrapTM mass spectrometer. The scheduled SRM mode demonstrates better results in all fields: more data points per peak, better reproducibility (coefficients of variation (CVs) <5%) and higher signal-to-noise ratio (S/N), even when the number of SRM transitions is doubled. The use of scheduled SRM mode instead of the classical one gives an enhancement of the limits of quantification by a factor two or even higher (up to six), depending on the analyte transitions

Multiresidue determination of 256 pesticides in lavandin essential oil by LC/ESI/sSRM: advantages and drawbacks of a sampling method involving evaporation under nitrogen

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Multiresidue determination of 256 pesticides in lavandin essential oil by LC/ESI/sSRM: advantages and drawbacks of a sampling method involving evaporation under nitrogen

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The Sampling Method by Evaporation under Nitrogen as a Complementary Approach for the Multiresidue Analysis of 256 Pesticides in Lavandin Essential Oil by LC/ESI/sSRM

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Multiresidue Analysis of 256 Pesticides in Lavandin Essential Oil by LC/ESI/sSRM: Advantages and Drawbacks of a Sampling Method by Evaporation Under Nitrogen

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