Rapid Sample Preparation Method with High Lipid Removal Efficiency for Determination of Sulphuric Acid Stable Organic Compounds in Fish Samples

Abstract

A rapid and low-cost sample preparation method modifying the so-called QuEChERS (quick, easy, cheap, effective, rugged and safe) method was developed for the determination of H2SO4 stable organic compounds in fish samples. The method involves acetonitrile salting-out extraction and a novel clean-up procedure combining the pH-tuned dispersive liquid–liquid microextraction (DLLME) with conc. H2SO4 digestion. The H2SO4 treatment is carried out by a simple operation in contrast to laborious and time-consuming procedures reported in the literature. The method was developed, optimised and validated using selected polybrominated diphenyl ethers (PBDEs) as representatives of H2SO4 stable compounds. For instrumental analysis of sample extracts, thermal desorption–gas chromatography–triple quadrupole tandem mass spectrometry (TD–GC–QqQ-MS/MS) was used. The proposed sample preparation method provides better co-extractives removal efficiency as compared to the original QuEChERS method and, unlike the QuEChERS dispersive solid-phase extraction (dSPE), allows complete removal of fatty acids. The sample preparation is low-cost due to the employment of small amounts of low-cost chemicals (no need of expensive sorbents), and it does not require special instrumentation. The whole analytical method showed satisfactory performance (linearity, recovery, repeatability, accuracy, limits of the method), and its applicability was confirmed by determination of PBDEs in samples of four fish species with variable lipid content in the range of 0.7–19%. The obtained recoveries for six PBDEs in the NIST standard reference material SRM 1946 were in the range of 81–95%, and relative standard deviations were in the range of 3–13%.