Investigation by photoacoustic spectroscopy of the effect of drying conditions on the depth-distribution of compounds on TLC plates

Photoacoustic spectroscopy (PAS) has been used to investigate the influence of the plate-drying process (in a dryer, in a current of warm air, or in a mbient air) on the depth-distribution of compounds inside the sorbent layer of TLC plates. The results obtained by PAS studies from different TLC plat es were compared with those obtained by reflectance mode slit-scanning dens itometry Use of different drying conditions resulted in significant differe nces between PAS signals obtained from the same compound in the uppermost 6 2 mu m layer of the sorbent. The largest differences were between the plate s dried in ambient air and those dried in a dryer or in a current of warm a ir.