Determination of the beta-blocker betaxolol and labelled analogues by gas chromatography/mass spectrometry with selected ion monitoring of the alpha-cleavage fragment (m/z 72).
Low concentrations of betaxolol in blood plasma and physiological buffers were determined by selected ion monitoring of the intense m/z 72 fragment [CH2 = NH-CH(CH3)2]+ formed by electron impact ionization of the O-trimethylsilyl derivative. At a mass spectrometric resolution of 3000, fewer potentially interfering peaks were seen than at low resolution. There remained a chemical interference, corresponding to 100 pg/sample, which arose during treatment of the samples. This method is more sensitive than previous ones, but it is restricted to situations where the specificity can be controlled. When the m/z 72 fragment was mass-shifted by using betaxolol appropriately labelled with deuterium or 13C, both the interference and the baseline noise were greatly reduced; concentrations of labelled betaxolol as low as 10-20 pg/sample can be determined with little difficulty.
Lee
C R
CR
Laboratoires d'Etudes et de Recherches Synthélabo (LERS), Bagneux, France.
Coste
A C
AC
Allen
J
J
D000319:Adrenergic beta-Antagonists / Q000032:analysis* / Q000138:chemical synthesis; D000818:Animals; D015784:Betaxolol; D055598:Chemical Phenomena; D002621:Chemistry; D004285:Dogs; D008401:Gas Chromatography-Mass Spectrometry; D007202:Indicators and Reagents; D011412:Propanolamines / Q000032:analysis* / Q000138:chemical synthesis
D000319:Adrenergic beta-Antagonists; D007202:Indicators and Reagents; D011412:Propanolamines; D015784:Betaxolol