液体乳检测

We have utilized an automated acid hydrolysis technology, followed by an abbreviated Soxhlet extraction technique to obtain fat from whole milk for the determination of persistent organic pollutants, namely polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and polychlorinated biphenyls. The process simply involves (1) pouring the liquid milk into the hydrolysis beaker with reagents and stan- dards, (2) drying the obtained fat on a filter paper and (3) obtaining pure fat via the modified Soxhlet extraction using 100 mL of hexane per sample. This technique is in contrast to traditional manually intense liquid-liquid extractions and avoids the preparatory step of freeze-drying the samples for pressurized liquid extractions. Along with these extraction improvements, analytical results closely agree between the methods, thus no quality has been compromised. The native spike (n = 12) and internal standard (n = 24) precision and accuracy results are within EPA Methods 1613 and 1668 limits. While the median (n = 6) Toxic Equivalency Quotient (TEQ) for polychlorinated dibenzo-p-dioxins/polychlorinated diben- zofurans and the concentration of the marker polychlorinated biphenyls show a percent difference of 1% and 12%, respectively, compared to 315 previously analyzed milk samples at the same laboratory using liquid-liquid extraction. During our feasibility studies, both egg and fish tissue show substantial promise using this technique as well

Polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) are classes of related environmental pollutants produced through diverse sources or industrial use and are known to strongly bio-accumulate and produce multiple toxic endpoints in animals and humans 1,2 . The 2,3,7,8- tetrachlorodibenzobenzo-p-dioxin (TCDD) isomer has been classified as a group 1A human carcinogen by IARC 2 . PCBs with dioxin-like properties are often measured with the PCDD/Fs. These three classes of chemicals are listed as persistent organic pollutants (POPs) by the Stockholm convention designated for world-wide reduction in the environment 1 .The primary route of non-occupational human exposure to PCDDs and PCDFs is foods and animal feeds 3-5 . Monitoring programs established are aimed to aid efforts to control contamination in foods and animal feeds 5 . Central to these efforts are confirmatory methods capable of measuring these chemicals at low concentrations in foods. We investigated an orbital trapping mass spectrometer for the measurement of PCDD/Fs and PCBs at low concentrations in whole cow’s milk.

The C. Gerhardt HydrothermTM – SoxthermTM system was designed as an automated Weibull-Stoldt Fat Determination system. Acid hydrolysis of the sample takes place; the fat is allowed to dry on a filter. The fat is extracted from the filtration residue with an organic solvent; the solvent is evaporated and dried for fat determination. With some method modifications, it is being used as the first step (extraction) of POPs from high fat matrices.