In order to evaluate the efficiency of biobeds on DTC degradation, the aim of this study was to apply, optimize and validate a method to determine dithiocarbamate (mancozeb) in biobeds using gas chromatography-tandem mass spectrometry (GC-MS).

The DTC pesticide mancozeb was hydrolysed in a tin (II) chloride solution at 1.5% in HCl (4 mol L⁻¹), during 1 h in a water bath at 80 °C, and the CS₂ formed was extracted in isooctane. After cooling, 1 mL of the organic layer was transferred to an auto sampler vial and analyzed by GC-MS.

A complete validation study was performed and the following parameters were assessed: linearity of the analytical curve (r²), estimated method and instrument limits of detection and limits of quantification (LODm, LODi, LOQm and LOQi, respectively), accuracy (recovery%), precision (RSD%) and matrix effects. Recovery experiments were carried out with a standard spiking solution of the DTC pesticide thiram. Blank biobed (biomixture) samples were spiked at the three levels corresponding to the CS₂ concentrations of 1, 3 and 5 mg kg⁻¹, with seven replicates each (n = 7).

The method presented satisfactory accuracy, with recoveries within the range of 89–96% and RSD ≤ 11%. The analytical curves were linear in the concentration range of 0.05–10 µg CS₂ mL⁻¹ (r² > 0.9946). LODm and LOQm were 0.1 and 0.5 mg CS₂ kg⁻¹, respectively, and the calculated matrix effects were not significant (≤ 20%). The validated method was applied to 80 samples (biomixture), from sixteen different biobeds (collected at five sampling times) during fourteen months. Ten percent of samples presented CS₂ concentration below the LOD (0.1 mg CS₂ kg⁻¹) and 49% of them showed results below the LOQ (0.5 mg CS₂ kg⁻¹), which demonstrates the biobeds capability to degrade DTC.

为了评估生物床对DTC降解的效率，本研究的目的是应用，优化和验证使用气相色谱-串联质谱（GC-MS）测定生物床中二硫代氨基甲酸酯（mancozeb）的方法。

将DTC农药代森锰锌在1.5％的HCl（4 mol L ^-1）的氯化锡（II）溶液中于80°C的水浴中水解1小时，并将形成的CS ₂萃取至异辛烷中。冷却后，将1 mL有机层转移至自动进样器样品瓶中，并通过GC-MS分析。

进行了完整的验证研究，并评估了以下参数：分析曲线的线性（r ²），估计的方法和仪器的检出限和定量限（分别为LODm，LODi，LOQm和LOQi），准确性（回收率％） ），精度（RSD％）和矩阵效果。使用DTC农药噻吨的标准加标溶液进行回收实验。将空白生物床（生物混合物）样品加标为与CS ₂浓度分别为1、3和5 mg kg ^-1的三个水平，每个重复7次（n = 7）。

该方法具有令人满意的准确性，回收率在89–96％范围内，RSD≤11％。在0.05–10 µg CS ₂ mL ^-1的浓度范围内，分析曲线呈线性（r ² > 0.9946）。LODm和LOQm分别为0.1和0.5 mg CS ₂ kg ^-1，并且计算出的基质效应不明显（≤20％）。经过验证的方法在十四个月中应用于来自十六个不同生物床（以五个采样时间采集）的80个样品（生物混合物）。百分之十的样品的CS ₂浓度低于LOD（0.1 mg CS ₂ kg ^-1），其中49％的样品的结果低于LOQ（0.5 mg CS _2）kg ^-1），这证明了生物床降解DTC的能力。