Determination of serum nadolol levels by GLC--selected ion monitoring mass spectrometry: comparison with a spectrofluorometric method.

A method to determine the serum concentration of the beta-adrenergic receptor blocking agent, nadolol, by GLC--selected ion monitoring mass spectrometry of the tri(trimethysilyl) ether derivative is described. A basic solution of serum was extracted, known amounts of internal standard were added to the extract, and the extract was back-extracted into acidic media and lyophilized. The resulting solids were reacted with N-trimethylsilylimidazole. Coded serum samples of 12 subjects, given nadolol alone or in combination with a second drug, were analyzed. The ions at m/e 86 and 100 were monitored to establish the relative concentration ratio of nadolol and the internal reference N-methylnadolol. No interferences from blood components or other administered drugs were observed. A detection level of 6.95 ng/ml of serum was found.