## 4 Applications of Piezoelectric Materials in Analytical Chemistry
### Miscellaneous Applications  
[PERSON] et al. [166] determined the mass (concentration) of an aerosol using a piezoelectric crystal sensor. Humidity, temperature, particle accumulation characteristics, mass sensitivity, and response linearity were examined as five areas of influence. No reference crystal is used to compensate for changes in airflow temperature or humidity. By reducing the inlet temperature's rate of change, the error due to temperature was successfully reduced. The absorption and release of moisture by aerosol deposition caused the error due to humidity. The recorded linear response limitations for several aerosols and devices ranged from 0.2 \(\mu\)g/mm\({}^{2}\) to 6 \(\mu\)g/mm\({}^{2}\). Mass sensitivity was affected by sediment size and location. At particle sizes of 2 m in diameter, mass sensing was reduced, reaching 0 m to 20 m. In the size range of 2 \(\mu\)m-20 \(\mu\)m, plastic crystal coatings improved sensor performance. [PERSON] et al. [167] assert that the suspended particle's mass concentration can be determined using piezoelectric quartz as a microbalance. A collector, such as an electrostatic precipitator or an impactor, deposits suspended particles on the surface of the electrode of the vibrating crystal, and the resonance frequency lowers proportionally to the additional mass of the particles. The device's time resolution and high sensitivity were examined. An electrostatic precipitator that sampled at 1 L/min was utilized to measure the mass concentration of the particles in the air at 41 s to within 5%. [PERSON] [168] s described a portable direct reading device capable of monitoring particle mass concentrations in the range of about 50 \(\mu\)g/m\({}^{3}\) to 5000 \(\mu\)g/m\({}_{3}\). Vapors in the air, including water vapor, have no impact on the sensors. The chemisorption reactions of mono-, dimethyl-, and trimethylamine with piezoelectric crystals in vacuum systems have been studied at ambient temperature [169; 170]. For the solid substrate coating over the crystals, thin films of several metal salts such as ZnCl\({}_{2}\), FeCl\({}_{3}\), CoCl\({}_{2}\), ZnI\({}_{2}\), and HgBr\({}_{2}\) have been applied. The reactions were studied to find the optimal coating for detecting and identifying these dangerous amines with piezoelectric crystal detectors. Iron (III) chloride coating has immense potential. [PERSON] etc. [171] and [PERSON] [172] created a technique that makes use of piezoelectric crystals to measure the deposition rate and the thickness of the film. AT-cut crystals in thick slip mode with a vibration frequency of 2.5 MHz show a frequency variation of about 1 Hz per thickness of the metal accumulated over the exposed facets. On average, crystals can hold about 20,000 g (about 44.09 lb) of metal before the deposits need to be removed or new crystals need to be used. [PERSON] [173] used a solvent sorption detector to create a simple portable detector for studying the detection limits of various chemicals. Finally, quartz thermometers, quartz pressure transducers [174], and thin film thermocouples [175] are some other applications.