tailieunhanh - Analysis of Pesticides in Food and Environmental Samples - Chapter 2

The determination of pesticides in food and environmental samples at low concentrations is always a challenge. Ideally, the analyte to be determined would be already in solution and at a concentration level high enough to be detected and quantified by the selected final determination technique (., HPLC or GC). Unfortunately, the reality is far from this ideal situation. Firstly, the restrictive legislations from European Union and World Health Organization devoted to prevent contamination of food and environmental compartments by pesticides make necessary the development of analytical methods suitable. | 2 Sample Handling of Pesticides in Food and Environmental Samples Esther Turiel and Antonio Martin-Esteban CONTENTS Sample Extraction and Solid-Liquid Soxhlet Microwave-Assisted Pressurized Solvent Extraction . 42 Supercritical Fluid Extraction . 43 Liquid-Liquid Solid-Phase Polar Sorbents. 46 Nonpolar Sorbents . 48 Ion-Exchange Sorbents . 49 Affinity Sorbents. 49 Solid-Phase Microextraction . 52 Extraction. 53 Desorption. 54 Solid-Solid Extraction Matrix Solid-Phase Dispersion . 54 Other Treatments . 55 Stir Bar Sorptive Extraction . 55 Liquid Membrane Extraction Techniques . 55 Future Trends . 56 References . 56 2007 by Taylor Francis Group LLC. INTRODUCTION The determination of pesticides in food and environmental samples at low concentrations is always a challenge. Ideally the analyte to be determined would be already in solution and at a concentration level high enough to be detected and quantified by the selected final determination technique . HPLC or GC . Unfortunately the reality is far from this ideal situation. Firstly the restrictive legislations from European Union and World Health Organization devoted to prevent contamination of food and environmental compartments by pesticides make necessary the development of analytical methods suitable for detecting target analytes at very low concentration levels. Besides from a practical point of view even when the analyte is already in solution . water or juice there are several difficulties related to the required sensitivity and selectivity of the selected determination technique that must be overcome since the concentration of matrix-interfering compounds is much higher than that of