Optimisation, validation and application of the solid-liquid extraction with low-temperature purification followed by gas chromatography-mass spectrometry for determination of phthalates in sewage sludge

Abstract

ABSTRACT Sewage sludge is a by-product obtained from sewage treatment plants (STP) that can be used to improve physical and chemical properties of the soil. However, xenobiotic compounds such as phthalates can be found in this material. Thus, the objective of this study was to optimise and validate the solid-liquid extraction with low-temperature purification (SLE-LTP) for the determination of five phthalates in sludge samples. Analyses were performed by gas chromatography coupled to the mass spectrometry (GC-MS). The SLE-LTP optimised parameters were water volume, extraction solvent, shaking mode and, freezing time. The most advantage of the proposed method is that it did not require additional clean up of the extracts with sorbents. In the best condition of extraction, recoveries of the five target analytes ranged from 76% to 119% and relative standard deviations were lower than 15%. Limits of quantification were 40 μg kg−1 for four phthalates and 80 μg kg−1 for dietylhexylphthalate (DEHP), which were about 6 to 12 times lower than maximum residue limits (MRL) established by Brazilian legislation. The validate method was applied to sewage sludge collected from six municipalities of Minas Gerais. Approximately 83% of the analyzed samples were contaminated by some phthalate, mainly DEHP with concentration ranging from 0.78 to 10.24 mg kg−1.