Determination of preservatives in liquids by piezosensors

In the current study, piezosensors based on the molecularly imprinted polyimides with imprints of potassium sorbate and sodium benzoate were obtained. Molecularly Imprinted Polymers (MIPs) were synthesized using a polyimide and a non-covalent imprinting technique. It was established that the use of 0.1 g/mL template concentration at the thermochemical stage led to the formation of the maximum number of molecular imprints on the film surface. Using the scanning force microscopy, it was found that the reference polymer film had a uniform surface with a small height difference from 1.4 to 2.6 nm (including 88.94 % of pores with a radius of up to 10 nm) and had good film thickness reproducibility. The surface morphology of films of molecularly imprinted polymers with imprints of potassium sorbate and sodium benzoate had more developed surface, which was associated with the peculiarities of the formation of imprints. In this work, imprinting factor (IF) and selectivity coefficient (k) of the sensor were calculated. Molecularly imprinted polymers had better selectivity, sensitivity, and ability to recognize target template molecules than the reference polymers (non-imprinted polymers). Molecularly imprinted polymer-modified piezoelectric sensors (MIP sensors) have been used to analyze potassium sorbate and sodium benzoate in non-alcoholic drinks. The linear concentration range was identified to be 5 - 500 mg/L and the limit of detection for potassium sorbate and sodium benzoate were 1.6 mg/L and 2 mg/L, respectively. The determination of potassium sorbate and sodium benzoate in non-alcoholic drinks was carried out by MIP sensors and spectrophotometry method. The results obtained by the sensors and the spectrophotometry method were in good agreement. The concentration of preservatives for the potassium sorbate and the sodium benzoate in non-alcoholic drinks was 130 - 176 mg/L and 129 - 146 mg/L, respectively.