A computer-controlled system for generation of chemical vapours in in vitro dermal uptake studies

Background/aims: Recent work in our laboratory suggests that dermal absorption and desorption of volatile chemicals may be assessed in vitro by thermogravimetric analysis (TGA), i.e. by passing chemical vapour over a piece of skin while recording the weight increase at constant temperature and humidity. This paper describes a high-precision automated vapour-generating system for use with the TGA equipment.

Methods and results: The system consists of computer-controlled magnetic valves and mass flow meters that split and redirect a flow of pure, dry air through different stainless-steel gas wash bottles thermostated to 25.00±0.05°C. Each wash bottle is filled with a neat volatile chemical and designed so that the air leaving reaches 100% saturation within seconds, as shown with cyclohexanone. The air leaving the wash bottles are combined and directed via stainless-steel liners to the skin piece in the TGA chamber. The liners are heated to 30°C to prevent condensation of water or chemical. Special computer software was developed to allow automatic runs with different wash bottles (chemicals) and air flows over several days. A number of measurements were made to characterize the stability and reproducibility of the vapour-generating system.

Conclusions: We have developed a computer-controlled vapour-generating system for use in measurements of dermal absorption of chemicals by thermal gravimetry. The system has high stability and reproducibility and produces little noise.