Development of a piezoelectric crystal sorption detector for monitoring of total organic compounds in air

Abstract

A light and portable organic vapours monitor has been developed using piezoelectric (P/Z) quartz crystal to determine Volatile Organic Compounds (VOCs) commonly found in workplace air. Out of the eight coating material studied, High Vacuum Grease (HVG) was found to be the best for determining commonly encountered organic vapours such as 1,1,1-Trichloroethane, Chloroform, Benzene and Toluene in room air. The optimised coating weight was 23 μg HVG at a flow rate of 200 mL/min. Moisture was found to interfere and the use of a Nation gas dryer was found to reduce the relative humidity to a constant 37 % for room air with 43 - 81% relative humidity. Under optimised conditions, a mean sensitivity of 1.9 × 10-2 Hz/ppm was obtained for total VOCs with 17.2% RSD variation towards different VOCs. Excellent linear working ranges were obtained from 40 to 2400 ppm (v/v), with response time and recovery time within one minute up to 500 ppm (v/v) of analyte. High and relatively constant response factors were obtained for different VOCs. The reliability of the method has been established by parallel method comparison using established GC-FID method. The P/Z detector developed could also be used to monitor individual VOCs.