Comparison of different methods of extraction for incurred contaminants in fish

Poster presented at IUPAC 2014 by USDA
Yelena Sapozhnikova & Steven J. Lehotay
U.S. Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center; 600 East Mermaid Lane; Wyndmoor, PA 19038; USA

The goal of this study was to investigate variables impacting extraction yields of incurred pesticides and environmental contaminants: polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and flame retardants (FRs) in fish samples of white croaker and salmon. We sought to compare extraction efficiencies of different shakers and a probe blender as extraction devices. Another goal was to determine the most advantageous shaking/extraction time, sample size, and sample to solvent ratio, which yielded the maximum extraction amount of the incurred contaminants. Filter-vial dispersive solid-phase extraction with MgSO4 , Z-Sep, C18 and primary secondary amine sorbents were used for cleanup and low pressure vacuum outlet gas chromatography - triple quadrupole tandem mass spectrometry (LPGC-MS/MS) was utilized for quantification. NIST Standard reference material SRM 1947 (Lake Michigan Fish Tissue) was also analyzed as an additional control to assess extraction conditions and final method performance. Vortex shaking for 1 min with 1:1 sample:solvent ratio as in QuEChERS gave accurate and equivalent results as with the probe blender in most cases, but 10 min was better for certain analyte matrix pairs. Extraction by vibration shaking often needed 60 min to reach the same degree of extraction efficiency.

Method development and validation studies involving analysis of contaminants in food and environmental matrices often only use spiked samples to assess suitable method performance. Similarly, quality control (QC) samples after the method has been implemented are spiked with the analytes, not incurred, to check ongoing method performance.1 Even in the case of proficiency testing, spiked samples are usually sent to the labs for evaluation. Even if incurred samples are used, the actual analyte concentration may not be known for comparison with the experimental results. It is possible that all reported concentrations in real samples may be lower than actual because total extractability of analyte-matrix combinations is not tested for common monitoring methods employed worldwide. It is common knowledge that analytes are more easily extracted from laboratory-spiked tissues than from realworld incurred samples, which may have stronger analytematrix inter-actions to be overcome. However, few chemists actually develop or validate their methods using incurred samples, or ideally using Standard Reference Materials (SRMs) that have been rigorously characterized by different orthogonally-selective methods to determine a precisely known concentration.2 When developing new methods of extraction, side-by-side analysis of the same sample by both the reference method and new conditions need to yield the same result in order to demonstrate suitable method performance of the new method. This is known as a bridging study, and few labs conduct this type of study due to the extra time, effort, and cost involved, but the risk is inaccurate results, even if method validation, QC, and proficiency testing results meet required specifications. The aim of this study was to assess different QuEChERS 3 extraction conditions in the analysis of many pesticide residues and environmental contaminants in incurred fish samples of white croaker, salmon, and NIST SRM 1947 (Lake Michigan Fish Tissue). Type and time of extraction would be compared as well as sample size and sample:solvent (acetonitrile) ratio.

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Title

Comparison of different methods of extraction for incurred contaminants in fish

Description

The goal of this study was to investigate variables impacting extraction yields of incurred pesticides and environmental contaminants: polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and flame retardants (FRs) in fish samples of white croaker and salmon. We sought to compare extrac...

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