Abstract
The concept of thin-layer chromatography (TLC) "chemical diskette" is demonstrated whereby high performance liquid chromatographic (HPLC) effluents are delivered and stored along a linear path on a TLC surface. The time coordinate normally associated with the HPLC chromatogram is transformed therefore to a spatial coordinate on the solid matrices. After the HPLC analytes have been deposited on the TLC in a pre-determined pattern as controlled by a computer, the pattern can be retraced and interrogated by various spectroscopic methods. In the present demonstration, the analytes are detected by fluorescence where an optical fiber carries the laser beam for excitation. The LC/TLC diskette method was experimentally implemented by replacing the pen of a high resolution digital x-y recorder with the outlet tube of a microbore HPLC column. The writing rate and pattern of the LC effluent on the TLC plate were controlled by the x-y recorder as driven by a microcomputer. After removal of the LC solvent, the adsorbed analytes on the TLC surface were interrogated by retracing the pattern with the He-Cd laser irradiation as carried by the optical fiber on the pen holder. Other fibers on the same holder collect and transmit the fluorescent emission to the detection system. The detection limits were in the low femtomole range for two amino acids derivatized by naphthalenedialdehyde. Also, it was possible to detect di-derivatized lysine, which was not quenched as in the solution phase, on the TLC surface.
