Standardisation of a Vapour Generator for Calibration of Environmental Monitoring Instruments

Abstract

Very low vapour pressure of 2,4,6 trinitrotoulene (TNT) yields extremely low vapour concentrations at different flow rates in the air, yet considerable quantity of vapours and TNT
dust during handling may be present at the workplace environment which is harmful to the health of the personnel working there. The explosive vapours, such as TNT,  2,6-dinitrotoluene (DNT), etc., though harmful to the health of the personnel, are not covered either in the emission standards or in the ambient air quality standards. Presently, no instrument is available for air monitoring of TNT vapours. These vapours need to be collected on-site to estimate TNT concentration. Realising the need for real-time air monitoring of TNT, efforts have been made to understand and device an instrument for on-site determination of TNT vapours parts per billiion (ppb) range. Low-level TNT vapours and TNT buried in the soil in military operations are required to be detected. The instruments for this require careful calibration to yield accurate and reliable results. Hence, an effort has been made to develop a trace-level ppb vapour generator. The vapour generator of a spiral glass column of length 170 cm and inner diameter 4 mm 2 0.5 mm has been used. An activated charcoal glass tube has been used for sampling TNT vapours. The adsorbed TNT vapours were desorbed and analysed using high performance liquid chromatography. The
solid support used has been studied. These vapours generated at different flow rates have been evaluated. The calibrated instrument can be used for in situ and on-site analysis of samples of TNT and also for samples collected.