Use of experimental designs for the optimization of stir bar sorptive extraction coupled to GC–MS/MS and comprehensive validation for the quantification of pesticides in freshwaters

Abstract

Although experimental design is a powerful tool, it is rarely used for the development of analytical methods for the determination of organic contaminants in the environment. When investigated factors are interdependent, this methodology allows studying efficiently not only their effects on the response but also the effects of their interactions. A complete and didactic chemometric study is described herein for the optimization of an analytical method involving stir bar sorptive extraction followed by thermal desorption coupled with gas chromatography and tandem mass spectrometry for the rapid quantification of several pesticides in freshwaters. We studied, under controlled conditions, the effects of thermal desorption parameters and the effects of their interactions on the desorption efficiency. The desorption time, temperature, flow, and the injector temperature were optimized through a screening design and a Box-Behnken design. The two sequential designs allowed establishing an optimum set of conditions for maximum response. Then, we present the comprehensive validation and the determination of measurement uncertainty of the optimized method. Limits of quantification determined in different natural waters were in the range of 2.5 to 50 ng L(-1), and recoveries were between 90 and 104 %, depending on the pesticide. The whole method uncertainty, assessed at three concentration levels under intra-laboratory reproducibility conditions, was below 25 % for all tested pesticides. Hence, we optimized and validated a robust analytical method to quantify the target pesticides at low concentration levels in freshwater samples, with a simple, fast, and solventless desorption step.

Silicone rubber selection for passive sampling of pesticides in water

“…Second, TGAs were performed under a helium stream of 45 mL min −1 with a temperature ramp of 10 °C min −1 up to 500 °C (raw and conditioned SRs). The release of residual oligomers by chemical and thermal conditioning steps of SRs was also estimated by measuring weight loss between raw material mass and conditioned SR. Scan chromatograms were also acquired by TD-GC/MS analysis in full scan mode (TD: 300 °C, 15 min, helium at 75 mL min −1 ), as detailed in Assoumani et al [20], to identify some oligomers and validate the usefulness of the conditioning steps.…”

Rapid detection of chlorpyriphos residue in rice by surface-enhanced Raman scattering

“…3,4 CP can effectively kill different pests such as Cnaphalocrocis medinalis, planthopper, aphid and Pieris rapae, which are pernicious to various plants such as rice, wheat, cotton, vegetables, and fruit. 5 Currently conventional analytical methods have been applied for the monitoring of CP and related pesticide residues such as HPLC, 6,7 GC-MS, 8,9 and an enzyme inhibition method. 10 Nevertheless, they are time-consuming, complex-preprocessed and labor-intensive, which makes these analytical methods less attractive, and thus not suitable to screen and detect pesticide residues in the eld.…”

Optimization of ultrasonic-assisted extraction for determination of polycyclic aromatic hydrocarbons in biochar-based fertilizer by gas chromatography–mass spectrometry

“…The traditional approach for optimizing variables is the one-variable-at-a-time approach, which is very time consuming and sometimes inefficient because of the unknown interactions among variables. The response surface method (RSM) with BoxBehnken design (BBD) is a statistical tool for designing experiments, constructing models, evaluating the effects of multiple factors, and investigating optimum conditions [19,20]. The objective of this research was to develop an easy and robust method for the analysis of PAHs in biochar-based fertilizers using UAE and gas chromatography-mass spectrometry (GC-MS) for quantitation.…”