Iturriaga H, Coello J, Maspoch S, Porcel M
Departament de Química, Facultat de Ciències, Universitat Autònoma de Barcelona, Unitat de Química Analítica, Edifici Cn, Spain.
Anal Bioanal Chem. 2002 Sep;374(1):33-8. doi: 10.1007/s00216-002-1341-8. Epub 2002 Jun 25.
A kinetic-spectrophotometric method for the determination of theophylline, dyphylline and proxyphylline, based on their azo coupling reaction with the diazonium ion of sulfanilic acid after a treatment with alkali, is proposed. The absorbance is recorded from 340 to 600 nm every second during reaction for 90 s, and calibration is performed by partial least-squares regression, using first derivative spectra values. Mixtures containing 2.5-13 micro g mL(-1) dyphylline and proxyphylline, and 2-9 micro g mL(-1) theophylline were successfully resolved with root mean squared errors of prediction (RMSEP) of 0.4, 0.3, and 0.2 for dyphylline, proxyphylline, and theophylline, respectively. The proposed method was satisfactorily applied to the determination of the three compounds in a commercially available pharmaceutical preparation and provided results similar to those obtained by HPLC.
