A sensitive and specific method for isoniazid determination based on selective adsorption using an isoniazid ion-selective piezoelectric sensor

A selective, sensitive and simple ion-selective piezoelectric (ISP) sensor was developed for the direct determination of isoniazid (INH) in body fluids. Based on sensitive mass response of piezoelectric quartz crystal and selective adsorption/desorption across the modified film, the ISP sensor was fabricated by coating a PVC film containing activant on one electrode of a thickness-shear mode piezoelectric quartz crystal. The observed frequencies of ISP sensor were found to decrease with the increase of the INH concentration in a 0.1 M NaNO3 solution. In this paper, three activants, INH-phosphotungstate (I), INH-silicotungstate (II), and INH-[BiI4](-) (III), were synthesized and investigated. Calibration graphs were linear from 6 x 10(-8) to 2 x 10(-3) M for I, 2 x 10(-7) to 2 x 10(-3) M for II and 2 x 10(-7) to 2 x 10(-3) M for III, with detection limits 6 x 10(-8) M for 1, 2 x 10(-7) M for II and 2 x 10(-7) M for III, in a 0.1 M NaNO3 solution at pH 7.0 and 37 degrees C. Recoveries were from 98% to 102% with R.S.D. up to 2%. Results for real samples obtained by the proposed method agreed well with those obtained by the conventional pharmacopeia method. (C) 1999 Elsevier Science B.V. All rights reserved.