Piezoelectric Crystal Detectors for Environmental Pollutants

Abstract

This chapter discusses the piezoelectric crystal detectors for environmental pollutants. A block diagram of the simplest typical experimental setup is presented. The piezoelectric crystal is housed in the detector cell and driven by a low frequency transistor oscillator. The frequency of the crystal is monitored by a frequency counter modified by a digital-to-analog converter. Piezoelectric detectors are used for the detection of dissolved gases in aqueous solutions. Ammonia and hydrogen sulfide are determined utilizing gas-permeable membranes to isolate the crystal from the solution. The catalytic effect of bromide on the oxidation of iodine to iodate by permanganate in acidic medium is utilized for the determination of bromide with a piezoelectric crystal detector. Iodide in solution is determined by means of a piezoelectric crystal with silver electrodes connected to a normal TTL oscillator. The effect of metal ions on a piezoelectric crystal in aqueous solution and the adsorptive determination of Fe(III) as phosphate is studied.