Determination of formaldehyde in production solutions using the piezoelectric sensors

In the current work, piezoelectric sensors based on a molecular imprinted polymer (MIP) were obtained for determining the formaldehyde in the industrial solutions of a woodworking plant. The synthesis was carried out directly on the surface of the piezoelectric sensor. In the process of the two-stage thermoimidization of the obtained prepolymerization mixture, a molecular imprinted polyimide of formaldehyde was formed. For the analysis of the supra-resin part of the effluent of the Grafskaya kuhnya LLC (Voronezh) woodworking enterprise, which was obtained by the dry distillation of wood, the method of a calibration graph having a linear relationship was used; the coefficient of determination R2 = 0.97. The detection limit of the piezosensor was 0.6 ∙ 10–4 mol / dm3, the range of determined concentrations was 1.0 – 10–4 mol / dm3. The comparison of piezoelectric sensors based on the polymer without imprints and based on the polymer with imprints of formaldehyde showed high selectivity of the latter for the target molecule. The calculated imprinting factor was 28.3, the coefficient of selectivity with respect to phenol was 0.05, which indicated the selectivity of the modified sensor to formaldehyde. The verification of the correctness of the determination of formaldehyde in the model and production solutions was carried out using the "added-found" method. It was found that the MIP-based sensor was sensitive only to formaldehyde, the relative standard deviation did not exceed 2.0%. In order to assess the effect of the object matrix (formaldehyde) on the value of the resonant frequency, the standard addition method was used. It was determined that the matrix did not affect the value of the analytical signal, the relative standard deviation was 2.8%. For the re-analysis, the piezoelectric sensor was exposed to the regeneration in the oven at 50 ⁰С. The proposed method for determining the concentration of the formaldehyde using the MIP-sensor allowed controlling the content of the toxicant in the industrial solutions.