| The properties of piezoelectric crystal detectors have generated considerable interest over the past twenty years in the area of analytical chemistry. Applications have been reported in air pollution monitoring, elemental analysis, and use of gas chromatographic detectors, among others. The most important property is the relationship between the mass added to the piezoelectric crystal surface and the change in crystal oscillating frequency. Several basic equations have been derived by Lostis, Sauerbrey and Stockbridge. The simplest form of these is given by the expression: {dollar}Delta{dollar}F = {dollar}-{dollar}K{dollar}Delta{dollar}M where {dollar}Delta{dollar}F is the change in oscillating frequency in Hz, K is a constant referring to the basic frequency of the quartz plate and the area coated, and M is the mass added in grams. The theoretical detection limit of the mass detector has been reported as being approximately 10{dollar}sp{lcub}-12{rcub}{dollar}g.; Detectors have been developed for the determination of hydrogen chloride, acetoin (3-hydroxy-2-butanone) and cocaine in air. Hydrogen chloride was detected by conversion with magnesium thiosulfate to sulfur dioxide, which, in turn, displaced mercury from a mercurous ion solution. The mercury was subsequently detected as the mercury-gold amalgam onto an uncoated crystal. Neutralized semicarbazide was utilized as the coating material for the detection of acetoin. The anti-body, anti-benzoyl ecgonine, was utilized as the coating material for cocaine.; These detectors demonstrated possible further application of piezoelectric crystal detectors in the areas of air pollution monitoring, as well as feasibility of use in law enforcement regulatory areas, where certain types of contraband food products or illicit drugs of abuse must be detected.; Instrumental developments and detailed results of measurements of sensitivity, response and recovery times, interferences, lifetimes, limits of detection, as well as possible use of the device as a field detector, will be presented. |
