Sorption properties of modifiers of piezoquartz resonators based on 3d-elements

Abstract

Transition metals are complexing substances, that is why being incorporated into the sensor modifiers, they can improve detection discrimination. The method of piezoelectric microweighting was used to study the sorption characteristics of the films based on partially soluble phosphates of 3d-elements (manganese (II), iron (II and III), nickel, copper, zinc, chromium) and coatings bearing partially soluble ferrous salts (hydrated oxide, fluoride, carbonate, sulfide, phosphate). The salts were created immediately prior to analysis, with bee glue as a filming agent. The method of immersion sensors in suspension of the filming agent and partially soluble salt, that was kept homogeneous by ultrasonic bath, was recognized the best way of film formation. Sorption characteristics of the composed coatings of piezoelectric resonator were estimated by the area under sorption kinetic curve and by peak value of sensor oscillation frequency drop during analysis of equilibrium gaseous form received over pure substances (water, phenol, isopropanol, isobutanol, acetous acid, chloroform, benzene, toluene, acetone, ethyl acetate, ammonia, diethyl amine, triethylamine, tert-butylamine, benzylamine). It was possible to determine the identifying variables Aij, minimax values of those allow to detect individual substances in the mixed vapour. Modifier application of piezoelectric resonators of phosphates of different 3d-elements is more efficient than use of different salts of one element. The shortcoming of the proposed modifiers is temporarily stable amine (ammonia) complexation. Those analytes desorption from the films proceeds slowly, it is determined by the bond strength of complexes and takes from 2 to 6 hours. However, array of seven sensors, modified by phosphates of transition metals of group IV, allows to detect oxygen- and nitrogen-based compounds vapours in the mixed vapour as well as to detect ammonia, diethyl amine and triethylamine individually.)