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

An ion-selective piezoelectric (ISP) sensor was successfully applied for the determination of niacinamide in serum and urine. By coating a polyvinylchloride membrane containing niacinamide-silicotungstate on one electrode of a thickness-shear mode piezoelectric quartz crystal, the ISP device can adsorb niacinamide selectively. The amount of coating applied to the crystal was calculated from the Sauerbrey equation by monitoring the frequency change. The logarithm of the frequency shift was linear with the logarithm of niacinamide 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 proposed method were in good agreement with those obtained by the conventional methods.