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


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 degrees 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 degrees 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.
Rauma
Matias
M
Work Environment Toxicology, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden. matias.rauma@ki.se
Johanson
Gunnar
G
D000279:Administration, Cutaneous; D004360:Drug Therapy, Computer-Assisted / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D019544:Equipment Failure Analysis; D017022:Flow Injection Analysis / Q000295:instrumentation* / Q000379:methods; D005740:Gases / Q000008:administration & dosage / Q000737:chemistry* / Q000493:pharmacokinetics*; D006801:Humans; D012869:Skin Absorption / Q000502:physiology*; D013818:Thermogravimetry / Q000295:instrumentation* / Q000379:methods
D005740:Gases