CONTACT SPOTTING - NEW APPROACH TO SAMPLE APPLICATION IN THIN-LAYER CHROMATOGRAPHY

The introduction of high-performance adsorbent layers to thin-layer chromatography has necessitated improved methods of sample application in order to realize fully the resolution, sensitivity and speed achievable with this quantitative analytical technique. Systems utilizing microcapillary pipettes are capable of maintaining minimal sample spot diameters; but when the solution viscosity is high or the concentration of analyte is small, this method of delivery may be impractical or may require a large number of serial applications to the same spot. The process described in this paper enables rapid concentration of sample solutions of up to 50 μl with transfer of the residue directly to the plate resulting in spot diameters as low as 0.1 mm located with excellent precision. Multiple samples are applied simultaneously, and the densitometric measurement of separated components is highly reproducible. The method is particularly valuable in dealing with samples of biological origin where concentrated extracts are too viscous to permit delivery by micropipettes. © 1979.