Plasma prednisolone concentrations: comparison of radioimmunoassay and competitive protein binding assay

Quantitative methodology for corticosteroids based on chemical oxidation to electrophilic products for electron capture-negative chemical ionization using capillary gas chromatography-mass spectrometry. I. Assessment of feasibility in the analysis of horse urine for dexamethasone

Sensitive and specific methodology based on capillary column gas chromatography-electron capture-negative chemical ionization-mass spectrometry has been developed for the quantitative analysis of corticosteroids from biological fluids. The feasibility of this method is demonstrated in the quantitative analysis of dexamethasone in horse urine following administration of the drug. A structurally similar compound, 6 alpha-methylprednisolone, is added to the urine as an internal standard. The free dexamethasone and the internal standard are extracted and oxidized to high-electron-affinity 1,4-androstadiene-3,11,17-trione structural analogs and then analyzed by capillary column gas chromatography-electron capture-negative chemical ionization-mass spectrometry.

Quantitative determination of betamethasone and its major metabolite in equine urine by micro-liquid chromatography-mass spectrometry

Micro-liquid chromatography-mass spectrometry (micro-LC-MS) was utilized to quantitatively determine betamethasone and its major unconjugated metabolite, 6 beta-hydroxybetamethasone, in equine plasma and urine. The advantage of micro-LC-MS over conventional gas chromatography-mass spectrometry in corticosteroid determination is illustrated and the reliable, steadfast nature of micro-LC-MS is demonstrated through example.

Qualitative detection of corticosteroids in equine biological fluids and the comparison of relative dexamethasone metabolite/dexamethasone concentration in equine urine by micro-liquid chromatography-mass spectrometry

Several important corticosteroids were qualitatively determined in the plasma and urine of horses by micro-liquid chromatography-mass spectrometry (micro-LC-MS). The sensitivity and specificity of micro-LC-MS are demonstrated as is the ability of micro-LC-MS to deal with endogenous interferences. In turn, the relative amount of dexamethasone and its major unconjugated metabolite were determined in equine urine by micro-LC-MS; the conclusions drawn are reported.