Quantitative determination of metoprolol in plasma and urine by gas chromatography

Abstract: A procedure for the gas chromatographic determination of the β‐receptor blocking agent metoprolol at therapeutic levels in plasma and urine is described. Metoprolol is made electron capture sensitive by a derivatization reaction with trifluoroacetic anhydride. The method permits determination of concentrations of metoprolol down to about 5 ng/g of sample with a standard deviation of 0.7 ng. Automation of the gas chromatographic procedure gives a capacity of 24 samples a day.