Screening for estrogenic steroids in sheep and chicken by the application of enzyme-linked immunosorbent assay and a comparison with analysis by gas chromatography–mass spectrometry

A total of 146 sheep urine and 87 chicken muscle samples collected from birds sold in the State of Kuwait local market (originating from Brazil, Denmark, France and Turkey) were tested for residues of two xenobiotic estrogenic compounds, namely diethylstilbestrol (DES); and ethinylestradiol. The samples were analyzed using enzyme-linked immunosorbent assay (ELISA) and gas chromatography–mass spectrometry (GC–MS). Data obtained showed that the levels of DES and ethinylestradiol in the urine ranged from not-detected (ND) to 1.2 and ND to 0.90 ppb, respectively. In the chicken muscle, the levels encountered were ND to 0.70 and ND to 0.30 ppb, respectively, indicating that some samples may show some activity in terms of a residue, as recommended by international organizations. In view of the results obtained by ELISA, the employment of a cut-off value of 0.30 ppb would make it reasonable to obtain low false-positive results, thus indicating that such a technique provides a fast and reliable method for the detection and screening of anabolic samples. All samples (both negative and positive) were subjected to GC–MS analysis for confirmatory purposes. The results obtained from the GC–MS analysis were found to be negative. These results show that the activity seen and reported above was due to the matrix of the samples, but not due to the active estrogenic compounds. Data on extraction recovery and coefficient of variation are also reported.