Selective pressurized liquid extraction of polychlorinated dibenzo-p-dioxins,

Journal of Chromatography A, 1138 (2007) 55–64

Selective pressurized liquid extraction of polychlorinated dibenzo-p-dioxins, dibenzofurans and dioxin-like polychlorinated biphenyls from food and feed samples
o Karin Wiberg a,∗ , Sune Sporring b , Peter Haglund a , Erland Bj¨ rklund b
a

Environmental Chemistry, Department of Chemistry, Ume˚ University, SE-901 87 Ume˚ , Sweden a a bDepartment of Analytical Chemistry, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden Received 11 May 2006; received in revised form 26 October 2006; accepted 30 October 2006 Available online 15 November 2006

Abstract Selective pressurized liquid extraction (PLE) of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (dl-PCBs) from various food andfeed samples was performed with a selective PLE method previously developed for bulk PCBs. The method utilizes sulfuric acid impregnated silica inside the extraction cell to oxidize coextracted fat. Extractions were performed at 100 ◦ C with n-heptane for 5 min in two cycles. Data obtained by selective PLE combined with gas chromatography/high-resolution mass spectrometry (GC-HRMS) were comparedto concentrations derived from reference laboratories applying conventional sample preparation and GC-HRMS. Experiments performed on spiked vegetable oil, naturally contaminated crude fish oil and oil containing compound feed samples showed good results for these relatively simple matrices. The accuracy was generally ±20% as compared to spiked levels or to values obtained by the referencelaboratories. The precision, measured as the relative standard deviation (RSD) for 2,3,7,8-tetrachlorodibenzo-p-dioxin toxic equivalency values (TEQs), was below 10% in all cases. The method was also tested on naturally contaminated herring tissue, chicken tissue, pork tissue and sepiolitic clay, which all caused some trouble. It was observed that sufficient amounts of sodium sulfate should be used fordehydration of tissue samples and additionally, the cells should not be packed too dense in order to avoid suppressed extraction efficiency. Once this was attended to, satisfactory data could be obtained, except for sepiolithic clay. This study demonstrates that selective PLE can be applied with success to a number of food and feed matrices in analysis of PCDD/Fs and dl-PCBs. Since the fat removalstep is on-line, the selective PLE method will reduce time and solvent consumption for sample preparation as compared to traditional clean-up. © 2006 Elsevier B.V. All rights reserved.
Keywords: Pressurized liquid extraction (PLE); Selective pressurized liquid extraction; Polychlorinated-p-dioxins; Polychlorinated furans; Dioxins; Polychlorinated biphenyls; Food; Feed

1. Introduction Theoccurrence of persistent organic pollutants (POPs) in our food supply is a threat to humans. In the Belgian dioxin crisis, feed was accidentally contaminated by polychlorinated biphenyl oil present in recycled fat, which regularly was used in feed production [1]. Unfortunately, these contaminants finally ended up in meat intended for human consumption. This put a great pressure on governmental as wellas private laboratories that had to analyze a large number of samples in a short time period, and highlighted the tediousness often associated with sample prepa-

∗

Corresponding author. Tel.: +46 907865672; fax: +46 90128133. E-mail address: karin.wiberg@chem.umu.se (K. Wiberg).

ration of samples to be analyzed at ultra-trace levels. The crisis was therefore an important incitement forgenerating new automated analytical extraction procedures as the extraction/cleanup step often is the bottleneck in analytical procedures. As a consequence, the European Commission (EC) initiated the research project DIFFERENCE [2] partly devoted to the development of improved analytical procedures for the analysis of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) and dioxin-like...