• The problem to be solved:
  Measurement of airborne volatile organic compounds

• Definition:
  Chemical sensor array with several non-selective, but differently sensitive chemical detectors. The surfaces are covered by sensing materials, so reversible interaction can be performed to detect chemical compounds in air. Improved computer programs can be taught to identify the analyses.

• Presentation:
  Piezoelectric quartz crystals with 9 MHz fundamental frequencies are used. The crystals are covered by different gas chromatographic stationary phases. The reference crystal is uncovered. The surface of the sensing layer is 0,2 cm². Relative measurements are performed by calculating the difference between sensing and reference crystals. Detectors are arranged in array in a thermostated PTFE cell. Digital thermostat is applied to maintain the temperature of the cell 40 ± 0.1 ^oC. High purity grade of nitrogen (99.999 %) is used as carrier gas. Nafion membrane drying unit is set into the analysis line to decrease the interference of moisture. Flow rate of carrier gas is controlled by computerised mass flow controller. The temperature inside the device is monitored by several 31 digit temperature measurement devices. Special PTFE tubing and fittings are applied to avoid the pollution and adsorption of the analyses through the walls of pipes. The investigated compounds are injected by syringe or connected by a sampling loop continuously to the analysis line. XILINX chip is used to perform data processing in a special computer card. Artificial neural network and pattern recognition computer programs are developed for identification of organic materials. The database of compounds is stored by computer and can be processed by commercial statistical computer programs. Principal component analysis can be made using Statistica for Windows^TM and fuzzy-clustering can be performed by MATLAB for Windows^TM Fuzzy Toolbox. Similar organic substances are discriminated by the sensor array and chemometric tools. The application of the sensor system is very advantageous for quick, on-filed analysis and to sign the presence of some volatile organic materials in air. The improved mathematical tools are able to evaluate the data set and calculate the results from the chemical analysis. The portable device has been proved to be proper solution to build monitoring system.

The chemical sensor array

• Application:
  Measurment of airborne

• Advantages:
  Volatile organic compounds are discriminated and determined in very low concentration range by the device and the connected computer system. The neural network of the computer can be taught to recognise several characteristic analyses in the workplace or environmental air samples. Dangerous materials (explosives, drugs, ammunition compounds) and groups of analyses can be identified by the sensor array very quickly.

• Stage of development: Prototype of the device is ready. Artificial neural network and pattern recognition data processing program is ready.
  

• Documentation available: Yes
  

• Name(s): Dr. György BARKÓ and Dr. József Hlavay

• Self introduction:
  Dr. György Barkó: Bs. (Mechanical Engineering, 1990), Ms. (Chemical Engineering, 1992), Ph.D. (Environmental Sciences, 1997)
  Dr. József Hlavay: Ms. (Chemical Engineering, 1971), Ph.D. (Chemical Engineering, 1985), D.Sc. (Chemical Engineering, 1993)

• Form: Patent pending application, Utility model pending application
• Priority:
• Countries where it is force:

• Name: Dr. György Barkó, University of Veszprém
• E-mail: barkogy@almos.vein.hu
• Fax: +3688 - 423203
• Phone: +3688 - 422022 / 4698, +3620 - 9807627
• Address: H-8201 P.O.B. 158. Veszprém, Hungary