In-Cell Clean-Up Pressurised Liquid Extraction Method to Determine Pesticides in Mushroom Compost by Gas Chromatography-Tandem Mass Spectrometry

A fast, simple, and easily automated method for the determination of two insecticides, diazinon and deltamethrin, and two fungicides, iprodione and prochloraz, in mushroom cultivation compost samples, based on selective pressurised liquid extraction (SPLE) and gas chromatography coupled to tandem mass spectrometry, is presented. The proposed method integrates extraction and clean-up processes in one single step, by adding a clean-up sorbent into the extraction cell. SPLE variables were thoroughly studied by experimental design. First, different clean-up sorbents and extraction solvents were screened at two temperature levels using a multifactor design; resulting Florisil and 1？:？1 acetone-dichloromethane the best combination. Then, temperature, extraction time, and sample-sorbent mass ratio were optimized by a central composite design. Best recoveries were obtained with a 0.4 sample-sorbent ratio, at 105°C and a 2？min extraction time. The SPLE method was characterized in terms of recovery (with values ranging from 81 to 103%), repeatability and intermediate precision (showing relative standard deviations less than 12% in most cases), and sensitivity (providing detection limits between 0.1 and 6？ng？mL？1). However, in spite of the clean-up process a matrix effect was observed and therefore standard addition calibration was recommended. 1. Introduction Compost for mushroom growing is made from several agricultural byproducts (straw, chicken manure, etc.) which are fermented and pasteurised. Therefore, the final product is formed by a complex mixture of nutrients resulting from the organic matter decomposition. During mushroom growing, chemicals such as fungicides, insecticides, or pesticides are added to the crop to maintain the mushroom immune to harmful insects, weeds, or microbes. After growing, exhausted substrate can be reutilised as supplement for crops, soil conditioner, mulch, agent of plant disease suppression, and soil bioremediation [1, 2]. Therefore, the levels and toxicity of these chemicals must be controlled in order to avoid environmental pollution and human exposure to pesticides. The origin, concentration, and degradation of several persistent organic pollutants such as polynuclear aromatic hidrocarbons (PAHs), polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins and -furans (PCDD/Fs) in compost have been studied [3] due to emerging concern about their impacts to the environment. Diazinon, iprodione, prochloraz, and deltamethrin (Figure 1) are pesticides commonly used in mushroom cultivation that are able to react as