Ion-selective piezoelectric sensor for niacinamide assay in serum and urine

An ion-selective piezoelectric (ISP) sensor was successfully applied for th e determination of niacinamide in serum and urine. By coating a polyvinylch loride membrane containing niacinamide-silicotungstate on one electrode of a thickness-shear mode piezoelectric quartz crystal, the ISP device can ads orb niacinamide selectively. The amount of coating applied to the crystal w as calculated from the Sauerbrey equation by monitoring the frequency chang e. The logarithm of the frequency shift was linear with the logarithm of ni acinamide concentration over the range from 1.0 x 10(-9) to 1.0 x 10(-3) M with a detection limit of 1.0 x 10-9 M at pH 7.0. Influencing factors were investigated and optimized. The results for real samples obtained by the pr oposed method were in good agreement with those obtained by the conventiona l methods. (C) 2001 Elsevier Science B.V. All rights reserved.