New approach for removing co-extracted lipids before mass spectrometry measurement of persistent of organic pollutants (POPs) in foods

Abstract

Persistent organic pollutants (POPs) methods for foods and animal feeds require sufficient sample intake followed by an extensive removal of interfering matrix components and concentration before a gas chromatographic mass spectrometry (GC-MS) method can be applied. The extraction dissolves associated lipids in animal foods or feeds. Methods must eliminate all co-extracted lipids before determination by GC-MS. A new approach for removing lipids is presented using basic silica gel or metal ion immobilized silica gel (Ag+) in a single step. Absorbent order, adsorbent amounts, and flow rates were found to be essential for consistent results. KOH/silica gel or Ag⁺ ion (AgNO₃) silica gel were both shown to retain 75-85% of the co-extracted lipids without using sulfuric acid. KOH/silica gel method applied to butter fortified at 7.3 pg TEQ/g lipid with polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) produced accurate results for all fortified congeners with 20% of predicted (n = 6). Ag⁺ silica gel incorporated into the Miura GO-EHT automated system produced similar results fortified at 3 pg TEQ/g lipid. During PCDD/F fortifications of butter with PCDD/Fs (n = 6), labeled standard recoveries for PCDD/Fs and planar polychlorinated biphenyls (PCBs) were all acceptable (52-99%) averaging 77% using the Miura system. A reduction in the amounts of sulfuric acid silica gel needed was possible in the completion of co-extractant removal. PCDD/F spikes into butter and for a spiked sunflower oil (PCDD/Fs and coplanar PCBs) were within ± 20% of the predicted using the Miura system; suitable for current methods criteria for foods including criteria in EU legislation.

Keywords: Foods; Lipids removal; PBDEs; PCBs; PCDD/Fs.