Determination of Melengestrol Acetate in Bovine Tissue: Collaborative Study

Abstract

Seven laboratories collaboratively studied a method for the assay of melengestrol acetate at the 0, 10, and 20 ppb levels in bovine fat, liver, muscle, and kidney. The study included fortification of tissue by each laboratory and analysis of fat samples taken from treated heifers which had endogenous levels of 0, 10, and 20 ppb melengestrol acetate. The multistep cleanup procedure used included extraction, solvent partition, column chromatography, and electron capture gas-liquid chromatographic determination. Results of the study for muscle, liver, kidney, and fat showed that the method gave satisfactory recoveries and accuracy. In fat, the most critical tissue, recovery was >93%. A statistical comparison of the results reported for fat tissue from treated heifers demonstrated that 5 of the 7 laboratories obtained similar results. The results produced by the method can be expected to be repeatable within and among laboratories. On the basis of the collaborative results the method has been adopted as official first action.

Fate of radioactive melengestrol acetate in the bovine

“…MGA Analysis. For determination of whether all of the radioactivity in fat, liver, kidney, and muscle was due to MGA, the tissues were subjected to the AOAC procedure (Krzeminski, et al, 1976) (Figure 2). The results 0 Amount in the 8:2 hexane-acetone fraction from Florisil columns (MGA method) as determined by scintillation counting.…”

“…Since MGA is administered to food-producing animals for 140-185 days, radioactive studies were carried out to determine the fate of MGA in feedlot heifers. Tracer studies were designed (1) to determine the distribution of radioactive MGA in various tissues, (2) to determine whether MGA was present intact in fat, muscle, kidney, and liver, (3) to determine whether the present assay method (Krzeminski et al 1976) would extract and quantitate all of the MGA present in tissues, (4) to identify the "marker compound" and "target tissue", and (5) to determine the extent of metabolism in the target tissue. EXPERIMENTAL SECTION Radioactive [3H]MGA Dose.…”

“…Twenty-five grams of fat was extracted with hot hexane and partitioned between hexane and acetonitrile. The MGA fraction was isolated on a Florisil column by elution with 8:2 hexane-acetone and quantitated by electron capture gas chromatography (Krzeminski et al, 1976).…”

Metabolism of [14C]mibolerone in the chicken

“…Florisil Column Chromatography. Florisil column chromatography was conducted as previously described (Krzeminski et al, 1976). In addition to the published elution sequence, methanol was used to recover additional radioactive compounds.…”

Determination and qualitative confirmation of melengestrol acetate residues in beef fat by electron capture gas chromatography and gas chromatographic/chemical ionization mass spectrometry

“…Various residue detection techniqueshave been developed with spectrophotometric (Krzeminski et al, 1968), gas chromatographic with flame ionization (Duggan, 1968(Duggan, , 1969, and gas chromatographic with electron capture (Krzeminski and Cox, 1973; Krzeminski et al, 1976; Ryan and Dupont, 1975) detection principles. Only the method of Ryan and Dupont has the required sensitivity to detect MGA residues at the low levels that might occur in animal tissues (Krzeminski et al, 1981).…”