Development of sample extraction and clean-up strategies for target and non-target analysis of environmental contaminants in biological matrices

Recently, there has been an increasing trend towards multi-targeted analysis and non-target screening methods as a means to increase the number of monitored analytes. Previous studies have developed biomonitoring methods which specifically focus on only a small number of analytes with similar physico-chemical properties. In this paper, we present a simple and rapid multi-residue method for simultaneous extraction of polar and non-polar organic chemicals from biological matrices, containing up to 5% lipid content. Our method combines targeted multi-residue analysis using gas chromatography triple quadrupole mass spectrometry (GC-QqQ-MS/MS) and a multi-targeted analysis complemented with non-target screening using liquid chromatography coupled to a quadrupole time of flight mass spectrometry (LC-QTOF-MS/MS). The optimization of the chemical extraction procedure and the effectiveness of different clean-up methods were evaluated for two biological matrices: fish muscle (lipid content ∼2%) and breast milk (∼4%). To extract a wide range of chemicals, the partition/extraction procedure used for the QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) approach was tested as the initial step for the extraction of 77 target compounds covering a broad compound domain. All the target analytes have different physico-chemical properties (log Kow ranges from -0.3 to 10) and cover a broad activity spectrum; from polar pesticides, pharmaceuticals, personal care products (PPCPs) to highly lipophilic chemicals such as polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and organochloride pesticides (OCPs). A number of options were explored for the clean-up of lipids, proteins and other impurities present in the matrix. Zirconium dioxide-based sorbents as dispersive solid-phase extraction (d-SPE) and protein-lipid removal filter cartridges (Captiva ND Lipids) provided the best results for GC-MS and LC-MS analysis respectively. The method was fully validated for samples of fish muscle and breast milk through the evaluation of recoveries, matrix effects, limit of quantification, linearity and precision (inter-day and intra-day). Mean recoveries (n=5) were between 70 and 120% with relative standard deviations (RSD) less than 20% in most of the cases. GC-MS/MS LOQs ranged from 0.08 to 3μg/kg and LC-QTOF-MS/MS LOQs ranged from 0.2 to 9μg/kg. The developed strategy was successfully applied for analysis of real samples; 22 target analytes were found in the breast milk samples and 10 in the fish samples. Non-target analysis allowed the detection and identification of an additional 14 contaminants and metabolites in the samples.