High frequency monitoring of pesticides in runoff water to improve understanding of their transport and environmental impacts.

Rainfall-induced peaks in pesticide concentrations can occur rapidly. Low frequency sampling may therefore largely underestimate maximum pesticide concentrations and fluxes. Detailed storm-based sampling of pesticide concentrations in runoff water to better predict pesticide sources, transport pathways and toxicity within the headwater catchments is lacking. High frequency monitoring (2min) of seven pesticides (Dimetomorph, Fluopicolide, Glyphosate, Iprovalicarb, Tebuconazole, Tetraconazole and Triadimenol) and one degradation product (AMPA) were assessed for 20 runoff events from 2009 to 2012 at the outlet of a vineyard catchment in the Layon catchment in France. The maximum pesticide concentrations were 387µgL-1. Samples from all of the runoff events exceeded the legal limit of 0.1µgL-1 for at least one pesticide (European directive 2013/39/EC). High resolution sampling used to detect the peak pesticide levels revealed that Toxic Units (TU) for algae, invertebrates and fish often exceeded the European Uniform principles (25%). The point and average (time or discharge-weighted) concentrations indicated up to a 30- or 4-fold underestimation of the TU obtained when measuring the maximum concentrations, respectively. This highlights the important role of sampling methods for assessing peak exposure. High resolution sampling combined with concentration-discharge hysteresis analyses revealed that clockwise responses were predominant (52%), indicating that Hortonian runoff is the prevailing surface runoff trigger mechanism in the study catchment. The hysteresis patterns for suspended solids and pesticides were highly dynamic and storm- and chemical-dependent. Intense rainfall events induced stronger C-Q hysteresis (magnitude). This study provides new insights into the complexity of pesticide dynamics in runoff water and highlights the ability of hysteresis analysis to improve understanding of pesticide supply and transport.

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

The determination of 256 multiclass pesticides in lavandin essential oil has been performed by liquid chromatography-electrospray ionization tandem mass spectrometry using the scheduled selected reaction monitoring mode available on a quadrupole-linear ion trap mass spectrometer. With the aim of improving the limits of quantification (LOQs) of the target molecules, a sampling step based on evaporation of the essential oil under a nitrogen flow assisted by controlled heating was tested. The LOQs determined in this case were compared with the values obtained with the classic dilution preparation method. With sampling by dilution, 247 pesticides were detected and quantified at low concentration, with 74 % of the pesticides having LOQs of 10 µg L(-1) or less. With the evaporation method, a global improvement of the LOQs was observed, with lower LOQs for 92 active substances and LOQs of 10 µg L(-1) or less for 82.8 % of the pesticides. Almost twice as many active substances had an LOQ of 1 µg L(-1) or less when the evaporation method was used. Some pesticides exhibited poor recovery or high variance caused by volatilization or degradation during the evaporation step. This behavior was evidenced by the case of thiophanate-methyl, which is degraded to carbendazim.

Changes in concentrations of fluoroquinolones and of ciprofloxacin-resistant Enterobacteriaceae in chicken feces and manure stored in a heap.

This study evaluated the impact of storing chicken manure on the degradation of enrofloxacin (ENR) and ciprofloxacin (CIP), and on the survival of CIP-resistant Enterobacteriaceae. At 24 d of age, half of 8900 chickens received ENR for 5 d. After the animals departed, their manure was stored in two heaps for 63 d. Enterobacteriaceae were cultured on media containing 0 to 32 mg L⁻¹ of CIP. A total of 320 isolates were fingerprinted using enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR) to evaluate community structure. Initial concentrations of ENR and CIP in the heap were 22 and 1.8 mg kg⁻¹, respectively. Seventy-three percent of the two fluoroquinolones were eliminated during storage. The administration of ENR led to a 5.1 log₋10 decrease in Enterobacteriaceae concentrations and emergence of CIP-resistant bacteria, which became dominant in the feces. concentrations decreased 1.2 to 2.3 log₋10 2 d after the heaps were made and continued to decline during storage. No resistant were found by Day 63. The highest CIP minimum inhibitory concentration (MIC) values observed among isolates of and of both and sp. were 128 and 4 mg L⁻¹, respectively. The dominant ERIC-PCR profiles changed over time. There was no relationship between genotype and resistance-isolated strains to CIP. Storing chicken manure in heaps appeared to be an effective way of limiting the entrance of CIP-resistant E. coli into the environment but did not prevent the dissemination of fluoroquinolones after land spreading.

Multiresidue analysis of multiclass pesticides in lavandin essential oil by LC/MS/MS using the scheduled selected reaction monitoring mode.

In this paper we describe the development of the first multiclass pesticide residue method applied to essential oils. A total of 70 pesticides covering a wide range of polarity and currently used on essential oil crops have been included in the method. The procedure consists of a 10-fold dilution of lavandin essential oil followed by a direct injection analysis by liquid chromatography/tandem mass spectrometry. The system used is an API 4000 QTrap equipped with an electrospray ionization interface and operating in scheduled selected reaction monitoring acquisition mode. Matrix effects were evaluated by comparing the slopes of matrix-matched and solvent-based calibration curves. Weak signal suppression or enhancement (<20%) was observed for most of the compounds. Method sensitivity was determined statistically by the injection of five matrix-matched calibration curves with the distribution's normality and the variance's homogeneity checked before establishment of a suitable regression model. Limits of detection (LODs) and quantification (LOQs) were then determined using the blank standard's deviation and the slope of the mean curve. The analytical method has been validated for 67 of the 70 pesticides and meets the following LOQs: ≤1 µg/L for 9 pesticides, ≤5 µg/L for 44, ≤10 µg/L for 9, and ≤20 µg/L for 5.

Effect of thiamethoxam on cockroach locomotor activity is associated with its metabolite clothianidin.

BACKGROUND: In the present study, the effect of thiamethoxam and clothianidin on the locomotor activity of American cockroach, Periplaneta americana (L.), was evaluated. Because it has been proposed that thiamethoxam is metabolised to clothianidin, high-performance liquid chromatography coupled with mass spectrometry was used to evaluate the amount of clothianidin on thiamethoxam-treated cockroaches. RESULTS: One hour after neonicotinoid treatment, the time spent in the open-field-like apparatus significantly increased, suggesting a decrease in locomotor activity. The percentage of cockroaches displaying locomotor activity was significantly reduced 1 h after haemolymph application of 1 nmol g(-1) neonicotinoid, while no significant effect was found after topical and oral administration. However, at 24 and 48 h, all neonicotinoids were able to reduce locomotor activity, depending on their concentrations and the way they were applied. Interestingly, it was found that thiamethoxam was converted to clothianidin 1 h after application, but the amount of clothianidin did not rise proportionately to thiamethoxam, especially after oral administration. CONCLUSION: The data suggest that the effect of thiamethoxam on cockroach locomotor activity is due in part to clothianidin action because (1) thiamethoxam levels remained persistent 48 h after application and (2) the amount of clothianidin in cockroach tissues was consistent with the toxicity of thiamethoxam.

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.

This paper illustrates the advantages of using the scheduled selected reaction monitoring (sSRM) algorithm available in Analyst 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 QTrap 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.

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

Experimental 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.

Protocols for optimizing MS/MS parameters with an ion-trap GC-MS instrument.

The product ion spectrum allows us to achieve very selective detection of pesticides and to eliminate the ambiguities caused by more conventional analytical approaches. Owing to the enhanced capabilities of GC/MS/MS for multiresidue pesticides, the development of a GC/MS/MS pesticides library will be useful. The aim of this study was to develop a sensitive and specific analytical method for the identification and quantification of compounds without the need of a time-consuming procedure. Two methods were studied in order to optimize the nonresonant conditions of dissociation of five pesticides (deltamethrin, metalaxyl, myclobutanil, procymidone, pirimicarb). The first permits a systematic investigation of the influence of the qz trapping parameter on sensitivity in precursor ion detection and on the efficiency of collision-induced dissociation (CID). The second is more suited for analytical laboratories and less time-consuming and allows us to reach similar results: the experiments were conducted step by step at a constant stability parameter.