Quantitative determination of 26 steroids in eggs from various species using liquid chromatography-triple quadrupole-mass spectrometry.

A method for analyzing 26 types of steroids in egg matrix was developed. The method used liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) in electrospray ionization mode (ESI). The procedure involved extraction with acetonitrile and removal of phospholipids by zinc chloride (ZnCl2) followed by SPE cleanup with a Plexa cartridge. The effect of ZnCl2 on phospholipid removal was directly observed using the post column infusion procedure. The SPE washing and elution conditions were optimized using a shallow gradient procedure. The free and conjugated steroids forms were determined using enzyme hydrolysis. The developed method resulted in satisfactory precision (RSD≤15%), and the limits of quantification were between 0.05 and 25 ng/g depending on the steroid types. The recoveries ranged from 63.2% to 121.5%. Finally, the developed method was successfully applied to compare the steroids in eggs from different species (i.e., hen, duck, quail and pigeon eggs) or different raising system (i.e., normal vs. organic eggs). The steroids can be clearly clustered according to species and raising system. The hierarchical clustering analysis indicated similarity of the steroids among the species. The developed method is sensitive and useful for detection and quantification of steroids in eggs and can be used for residue control programs. In addition, the observed steroid content will provide a fundamental reference for food risk assessment analysis.

A preliminary risk assessment of potential exposure to naturally occurring estrogens from Beijing (China) market milk products.

This study was conducted to determine the occurrence of the natural steroid hormones estrone (E1), 17α-estradiol (αE2), 17ß-estradiol (ßE2) and estriol (E3) in 38 commercial milk samples obtained from markets in Beijing, China. Liquid Chromatography coupled with tandem mass spectrometry (LC-MS/MS) was employed to determine estrogens levels. The concentrations of E1, αE2, ßE2 and E3 in different milk products varied from 0-146.12 ng/L, 0-70.12 ng/L, 0-31.85 ng/L to 0-2.18 ng/L, respectively. We compared exposures to estrogens through milk consumption with acceptable daily intakes (ADIs) and threshold for toxicological concern (TTC) to determine whether estrogen intakes from milk consumption are larger or smaller than the toxicity-based benchmarks. The combined margin of safety MOS (MOST) for total estrogens are about 72-99, 118-161, 539-1104, for 2-4, 4-7 year-old residential children, and adults, respectively. The lowest MOST for children of 2-4 years old result from comparing total of estrogens with the lowest TTC value (0.15 µg/person/day) (MOS=3.5). The MOS values suggest that the individual and total estrogens that may present in milk are not causing a health risk for the local residents, including young children.

Determination of xylazine and 2,6-xylidine in animal tissues by liquid chromatography-tandem mass spectrometry.

Xylazine is a potent α2-adrenergic agonist used in veterinary medicine for sedation, analgesia, muscle relaxation, and so on. Its residue in animal-derived food may cause the food safety problem. Moreover, the metabolite 2,6-xylidine was reported to be a genotoxic and carcinogenic compound. Therefore, it is necessary to develop a high sensitive method for analyzing xylazine and metabolite residue in animal products. Here, we described a LC-MS/MS method for simultaneous determination of xylazine and 2,6-xylidine in 4 animal tissues: liver, meat, kidney, and fat. The samples were extracted by acetonitrile, and further clean up by hexane. The analysis was performed on a C18 reversed-phase column and API 5000 Triple Quadrupole mass spectrometry with positive electrospray ionization interface operating in the multiple-reaction monitoring mode. For all of the investigated sample matrix, the limit of detection (limit of quantitation) for xylazine and 2,6-xylidine were 0.06 (0.2) and 1.5 (5) µg/kg, respectively, the recoveries were between 63.5% and 90.8%. The precision was within the range of required criteria for method development. The presented method is sensitive and reproducible, and thus suitable for accurate quantification of xylazine and metabolite residue in animal-derived food products.