The effect of organic solvents on the determination of cyclic boronates of some β-blockers by gas chromatography/mass spectrometry

Formation cyclic boronates for β-blockers, by use of triethylamine (TEA) and pyridine as catalysts, gives more effective product yield. Eleven β-blockers, formed by cyclic boronation with n-butylboronic acid and TEA, produced higher yields than by on-column thermal reaction and seven β-blockers were shown to give the highest yields in the phenyl cyclic boronation with pyridine or TEA by on-column thermal and general reaction. The phenyl cyclic boronate of nadolol produced one peak in the chromatogram and the n-butyl cyclic boronate showed two peaks. On-column derivatization with n-butylboronic acid and pyridine was effective in saving analysis time and for convenience, even though some n-butyl cyclic boronates by cyclic boronation with TEA gave a better yield. In n-butyl cyclic boronation with pyridine by on-column thermal reaction the detection limits were 0.1 to 4 ng/μL in urine with a signal-to-noise ratio of 10:1.