Determination of the beta-blocker carteolol in human plasma by a sensitive gas chromatographic-negative-ion chemical ionization high-resolution mass spectrometric method.

A specific and sensitive gas chromatographic-high-resolution mass spectrometric method for the determination of 5-(3-tert.-butylamino-2-hydroxy)propoxy-3,4-dihydrocarbostyril (carteolol), which is a beta-blocker giving depression of intraocular pressure, was developed to elucidate the pharmacokinetics of its ophthalmic application. Carteolol has been determined by high-performance liquid chromatography but with less satisfactory sensitivity. Carteolol was derivatized with pentafluorobenzoyl (PFB) amide followed by dimethylethylsilyl (DMES) ether, resulting in a high negative-ion current. The PFB-DMES derivative of carteolol was determined by the gas chromatography-negative-ion chemical ionization mass spectrometry (GC-NICI-MS) using selected-ion monitoring at low and high mass spectrometric resolution. the detection limit was less than 100 fg when the fragment ion was monitored at m/z 552.2067 in the NICI mode using methane as a reagent gas. The quantification limit of carteolol in human plasma with this method was less than 30 pg/ml. The proposed GC-MS method is considered to have sufficient specificity and sensitivity to study the pharmacokinetics of carteolol used as an ophthalmic solution.