VACUUM PLANAR CHROMATOGRAPHY (VPC) - A NEW VERSATILE TECHNIQUE OF FORCED FLOW PLANAR CHROMATOGRAPHY

Taking the disadvantage of capillary development and vapor phase effects into account, new methods of forced flow development have appeared. The new process of chromatographic development described is part of forced flow system. It is the vacuum (Pressure lower than atmospheric pressure) which is implemented in order to achieve the chromatographic development by inhaling of the mobile phase through the stationary phase, unlike the other forced flow methods which press the solvent. A complete development system was studied ; It consists of a plate positionning chamber and a membrane of polyethylene. In order to compartmentalize the useful surface of the chromatographic plate and to produce a soft pressure on the system without compression of the polymer. This material is a "closed cell" polymer (Recticel, Clichy, France) which makes it waterproof for the eluting solvent. The only path for the solvent during analysis is inside the adsorbant layer. Above this is a "Vacuum chamber" connected to a suction pump.This system creates a homogeneous depression at the level of the development chamber, then into the adsorbant layer and triggers a narrow application of the polymer on the chromatographic support. So, the depression thus obtained has the following effects : inhaling the eluent when the bottom of the set is dipping into a tank containing the solvent (forced flow system by inhaling), maintening the polymer membrane strongly applied on the adsorbant layer (micro chamber on depression) and suppressing the vapor phase the analysis progresses (vapor and dissolved gases contained in the layer) on the not chromatographic part of the plate. The plate remains dry and gas - free during the whole analysis. The advantages of this new system reside in the fact of not having to prepare the plate as in the classical method of thin - layer chromatography and contrarily to the other forced flow methods. On the other hand the first results obtained show that the development is like the vaporless phase development as for the forced flow system.