Development and application of a QuEChERS method with liquid chromatography-quadrupole time of flight-mass spectrometry for the determination of 50 wastewater-borne pollutants in earthworms exposed through treated wastewater

Abstract

Soil-dwelling earthworms are valuable sentinels in soil pollution monitoring and, in case of wastewater reuse for agricultural irrigation, they are continuously exposed to a multitude of organic micro-pollutants. In the present work, an analytical methodology for the determination of 50 wastewater-borne pollutants in earthworms (Lumbricus terrestris) using a fast extraction and sensitive detection method was developed. In total, 17 protocols based on QuEChERS extraction methods were evaluated including the choice of extraction salt (EN vs Original) and the solvent pH as well as the cleanup type. EN with cleanup on Oasis PRiME HLB (P-16) provided the best overall performance. Compound quantification was accomplished by liquid chromatography-mass spectrometry on a QToF-MS system using the ultra-fast high-resolution multiple reaction monitoring (MRMHR) mode. The method quantification limits ranged from 0.002 to 1.6 ng g−1. In comparison to previously reported methods the present protocol afforded improved accuracy with recovery rates exceeding 80%. The validated method was applied to the analysis of 36 earthworm samples originating from laboratory experiments and fields that had been irrigated with treated wastewater. Among the eight analytes detected in field samples, the highest concentration levels were measured for gemfibrozil (13 ng g−1) and caffeine (12 ng g−1). To the best of our knowledge, this is the first report of the transfer of wastewater-borne contaminants to earthworms following irrigation under natural farming practices.