DYNAMIC VAPOR GENERATOR FOR MODERATE AND LOW VOLATILITY COMPOUNDS

This paper describes the development, testing and application of a device capable of dynamically generating atmospheres containing stable concentrations of moderate to low volatility organic chemicals. The generator is of simple construction, being a glass tube packed with an inert support matrix that is physically coated with the appropriate test compound to be added to the atmosphere. The packed tube is located within a temperature controlled oven (typically a gas chromatograph oven is used) and is supplied with nitrogen carrier gas which can become equilibrated with the test component under the operational conditions applied. Based upon the volatility characteristics of the test compound or compounds present in the generator, judicious choice of carrier gas flow rate and oven temperature can provide an effluent gas stream that remains stable in component concentration over extended operational periods. The device has been applied to the formation of test atmospheres containing chlorpyrifos for the purpose of testing industrial hygiene adsorbent tubes used in air monitoring procedures.