Analysis of trace levels of pesticides in rainwater by SPME and GC-tandem mass spectrometry after derivatisation with PFBBr

New fully automated gas chromatographic analysis of urinary S-phenylmercapturic acid in isotopic dilution using negative chemical ionization with isobutane as reagent gas

The determination of urinary S-phenylmercapturic acid (S-PMA) represents the most reliable biomarker to monitor the intake risk of airborne benzene. Recently, the European Chemical Agency deliberated new occupational exposure limits for benzene and recommended an S-PMA biological limit value of 2-μg/g creatinine. This limit is an order of magnitude lower than the previous one, and its determination constitutes a challenge in the analytical field. We developed and validated a method that allows the fully automated and sensitive determination of S-PMA by the use of gas-chromatography negative chemical ionization tandem mass spectrometry in isotopic dilution. For negative chemical ionization, we selected a mixture of 1% isobutane in argon as reactive gas, by studying its chemical ionization mechanism and optimal parameters compared with pure isobutane or pure methane. This gas mixture produces a more abundant signal of the target analyte than isobutane or methane, and it extended the operative lifetime of the ion source, enabling us to start a high-throughput approach of the S-PMA analysis. Moreover, energy-resolved mass spectrometry experiments were carried out to refine the MS/MS analysis conditions, testing nitrogen and argon as collision gases. The method optimization was pursued by a chemometric model by using the experimental design. The quantification limit for S-PMA was 0.10 μg/L. Accuracy (between 98.3% and 99.6%) and precision (ranging from 1.6% to 6.4%) were also evaluated. In conclusion, the newly developed assay represents a powerful tool for the robust, reliable, and sensitive quantification of urinary S-PMA, and because of its automation, it is well suited for application in large environmental and biological monitoring.

Innovative Monitoring of Atmospheric Gaseous Hydrogen Fluoride

Hydrogen fluoride (HF) is a basic raw material for a wide variety of industrial products, with a worldwide production capacity of more than three million metric tonnes. A novel method for determining particulate fluoride and gaseous hydrogen fluoride in air is presented herewith. Air was sampled using miniaturised 13 mm Swinnex two-stage filter holders in a medium-flow pumping system and through the absorption of particulate fluoride and HF vapours on cellulose ester filters uncoated or impregnated with sodium carbonate. Furthermore, filter desorption from the holders and the extraction of the pentafluorobenzyl ester derivative based on solid-phase microextraction were performed using an innovative robotic system installed on an xyz autosampler on-line with gas chromatography (GC)/mass spectrometry (MS). After generating atmospheres of a known concentration of gaseous HF, we evaluated the agreement between the results of our sampling method and those of the conventional preassembled 37 mm cassette (±8.10%; correlation coefficient: 0.90). In addition, precision (relative standard deviation for n = 10, 4.3%), sensitivity (0.2 μg/filter), and linearity (2.0-4000 μg/filter; correlation coefficient: 0.9913) were also evaluated. This procedure combines the efficiency of GC/MS systems with the high throughput (96 samples/day) and the quantitative accuracy of pentafluorobenzyl bromide on-sample derivatisation.

Utilization of long duration high-volume sampling coupled to SPME-GC-MS/MS for the assessment of airborne pesticides variability in an urban area (Strasbourg, France) during agricultural application

Atmospheric samples have been collected between 14 March and 12 September 2012 on a 2-week basis (15 days of sampling and exchange of traps each 7 days) in Strasbourg (east of France) for the analysis of 43 pesticides. Samples (particle and gas phases) were separately extracted using Accelerated Solvent Extraction (ASE) and pre-concentrated by Solid Phase Micro-Extraction (SPME) before analysis by gas chromatography coupled to tandem mass spectrometry (GC-MS/MS). Four SPME consecutive injections at distinct temperatures were made in order to increase the sensitivity of detection for the all monitored pesticides. Currently used detected pesticides can be grouped in four classes; those used in maize crops (acetochlor, benoxacor, dicamba, s-metolachlor, pendimethalin, and bromoxynil), in cereal crops (benoxacor, chlorothalonil, fenpropimorph, and propiconazole), in vineyards (tebuconazole), and as herbicides for orchards, meadows of green spaces (2,4-MCPA, trichlopyr). This is in accordance with the diversity of crops found in the Alsace region and trends observed are in accordance with the period of application of these pesticides. Variations observed permit also to demonstrate that the long time sampling duration used in this study is efficient to visualize temporal variations of airborne pesticides concentrations. Then, long time high-volume sampling could be a simple method permitting atmospheric survey of atmospheric contamination without any long analysis time and consequently low cost.

Partitioning of the pesticide trifluralin between dissolved organic matter and water using automated SPME-GC/MS

Solid-phase microextraction (SPME) was used to determine the equilibrium association constant for a pesticide, trifluralin (TFR), with dissolved organic matter (DOM). After optimization of the SPME method for the analysis of TFR, partition coefficients (K DOM) with three different sources of DOM were determined in buffered solutions at pH 7. Commercial humic acids and DOM fractions isolated from two surface waters were used. The values of log K DOM varied from 4.3 to 5.8, depending on the nature of the organic material. A good correlation was established between log K DOM and DOM properties (as measured with the H/O atomic ratio and UV absorbance), in agreement with literature data. This is consistent with the effect of polarity and aromaticity for governing DOM-pollutant associations, regardless of the origin of DOM. This association phenomenon is relevant to better understand the behavior of pesticides in the environment since it controls part of pesticide leaching and fate in aquatic systems.

FI-photoinduced chemiluminescence method for diuron determination in water samples

A new method for the determination of the herbicide diuron, using a flow injection manifold and photoinduced chemiluminescence detection, is presented. The pesticide, in basic medium, was irradiated on-line with UV light (254 nm) for 53 s. A short discussion about the possible irradiation products is included. The chemiluminescent response of the photoproducts was induced by oxidation with potassium ferricyanide in phosphate buffer at pH 11.5. The method permitted the quantification of diuron over the 0.1-4.0 mg L(-1) range, with a detection limit (S/N = 3) of 20 µg L(-1) when the method was applied directly. However, the use of solid phase extraction (SPE) performed with C(18) cartridges allowed us to achieve a limit of detection of 0.4 µg L(-1) and a 1.5-30 µg L(-1) dynamic range. The method was successfully applied to the diuron determination in samples of water from different sources (spring, ground, mineral, irrigation, sea and tap waters) with a low consumption of reagents.

Development of an immunochromatographic assay for the rapid detection of bromoxynil in water

A rapid immunochromatographic one-step strip test was developed to specifically determine bromoxynil in surface and drinking water by competitive inhibition with the nano colloidal gold-conjugated monoclonal antibody (mAb). Bromoxynil standard samples of 0.01-10 mg L(-1) in water were tested by this method and the visual limit was 0.06 mg L(-1). The assay only required 5 min and one-step by dispensing a drop of sample solution onto a strip. Parallel analysis of water samples with bromoxynil showed comparable results from one-step strip test and ELISA. Therefore, the one-step strip test is very useful as a screening method for qualitative detection of bromoxynil in water.