Preparation and application of a trimethoprim ion-selective piezoelectric sensor

PVC film containing various activants was coated on one electrode of a thickness-shear mode piezoelectric quartz crystal (PQC) to fabricate a trimethoprim (TMP) ion-selective piezoelectric sensor for the determination of TMP. The method is based on the selective adsorption of TMP ion on the modified film and the sensitive mass response of the PQC. The method was found to be sensitive, rapid and easy to handle with no need for previous sample treatment. The logarithm of frequency shift of PQC was found to bear a linear relationship to the logarithm of the concentration of TMP over the range 2 x 10(-8)-2 x 10(-3) M with a detection Limit of 2 x 10(-8) M at pH 4.0. Recoveries were from 99-102.9%. Two activants, TMP phosphotungstate and TMP silicotungstate, were synthesized and investigated. Influencing factors were examined in detail and optimized. The results for real samples obtained by the proposed method agreed with those obtained by a conventional method.