Cresols are chemical contaminants derivative from phenol which can be found in sewage sludge. However, little attention has been given to monitoring these compounds in environmental matrices in the literature. Thus, the objective of this study was to develop a simple method based on solid-liquid extraction with low temperature purification for determining three cresol isomers in sludge. The quantification of these compounds was performed by gas chromatography coupled to mass spectrometry with a previous derivatization step. After a detailed study, the cresol recovery was higher than 91%, with relative standard deviation lower than 12% and a limit of quantification of 20 μg kg-1. Linearity was achieved between 10 and 90 μg L-1 (R2 > 0.98) with the standard solutions prepared in matrix extracts due to the trouble caused by the matrix effect. The proposed method was applied with success for monitoring cresols in sewage sludge samples coming from six different wastewater treatment plants. All samples showed contamination by cresols, mainly p-cresol with values between 32.3 and 516.9 μg kg-1. The majority of the analyzed samples showed a total sum of the isomers higher than the maximum residue limit established by Brazilian legislation (160 μg kg-1).

中文翻译：

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固相萃取-低温纯化-气相色谱-质谱法测定污水污泥中的三种甲酚异构体

甲酚是从苯酚衍生的化学污染物，可在污水污泥中发现。然而，在文献中很少关注监测环境基质中的这些化合物。因此，本研究的目的是开发一种基于固液萃取和低温纯化的简单方法，用于测定污泥中的三种甲酚异构体。这些化合物的定量是通过气相色谱法与质谱联用的，并使用先前的衍生步骤进行的。经过详细研究，甲酚的回收率高于91％，相对标准偏差低于12％，定量限为20μgkg-1。由于基质效应引起的麻烦，用基质提取物中制备的标准溶液可在10至90μgL-1之间实现线性（R2> 0.98）。所提出的方法已成功应用于监测来自六个不同废水处理厂的污水污泥样品中的甲酚。所有样品均显示出被甲酚（主要是对甲酚）污染的值，介于32.3和516.9μgkg-1之间。大部分分析样品显示，异构体的总和高于巴西法律规定的最大残留限量（160μgkg-1）。