Piezoelectric quartz crystal sensors based on ion-pair complexes for the determination of cinchonine in human serum and urine

A new sensing method for the determination of cinchonine was presented, based on the sensitive mass response of PQC and the selective adsorption of cinchonine on PVC membrane containing ion-pair complex. The proposed sensors show much wider working range (pH range), much higher sensitivity and selectivity than those potentiometric and spectrophotometric methods. In this paper, three counter ions were compared and six complexes synthesized. For the sensor modified with cinchonine-monotetraphenylborate-PVC membrane, calibration graph was linear over concentration range of 5×10⁻⁸-2.1×10⁻⁴ M with a detection limit of 4×10⁻⁸ M at pH 7.1, and recoveries 97.7-108.6%. Influencing factors were investigated in detail and optimized. Results from real samples were satisfactory.