ABSTRACT
Chromatographic Techniques .................................................................... 217 10.3 Progress in Rotation Planar Chromatography ........................................... 219
10.3.1 Introduction .................................................................................. 219 10.3.2 Classification and Separation Modes of RPC.............................. 219 10.3.3 Main Factors Influencing the Separation Speed .......................... 221
10.3.3.1 Mobile Phase Movement............................................. 221 10.3.3.2 Mobile Phase Flow Rate ............................................. 222
10.3.4 Adsorbent Bed.............................................................................. 222 10.3.5 Eluent Selection ........................................................................... 223 10.3.6 Typical Problems and Their Eliminations in RPC ...................... 223 10.3.7 Applications ................................................................................. 223
10.4 Progress in Overpressured Layer Chromatography................................... 224 10.4.1 Introduction .................................................................................. 224 10.4.2 Separation Modes and Methods of OPLC................................... 226
10.4.2.1 Transfusion, Infusion, and Infusion-Transfusion OPLC........................................................................... 226
10.4.2.2 Connection Possibilities of Operating Steps of OPLC ...................................................................... 226
10.4.2.3 Sample Transfer by OPLC to HPLC Separation ........ 228
10.4.2.4 One-and Multichannel OPLC Separations in the Adsorbent Layer Segmented by Flowing Eluent Wall.................................................................. 228
10.4.3 Theoretical Basis of OPLC .......................................................... 229 10.4.3.1 The Rule of Mobile Phase Movement
and Factors Influencing Retention .............................. 229 10.4.3.2 Efficiency Characteristics of OPLC
and Their Influencing Factors ..................................... 233 10.4.4 Basic Elements and Instruments of OPLC .................................. 237
10.4.4.1 Adsorbent Layers and Adsorbent Layer Systems for OPLC Separations ................................................. 237
10.4.4.2 Gas-and Water-Cushion Experimental and Commercial Instruments....................................... 237
10.4.4.3 OPLC Instruments with Cassette Systems.................. 238 10.4.4.4 One and Multichannel Experimental OPLC
Systems with Flowing Eluent Wall Configuration ..... 238 10.4.5 Applications of OPLC for Separation of Plant Substances ......... 238
10.4.5.1 Analytical Applications of OPLC in Phytochemistry.. 238 10.4.5.2 Preparative Applications.............................................. 242
10.5 The Role of Forced-Flow Planar Liquid Chromatographic Techniques for the Search of Natural Products ......................................... 243
Acknowledgment .................................................................................................. 244 References ............................................................................................................. 245
Column and layer liquid chromatographic techniques as supplementary techniques due to their arrangements have always been characteristically developed in constant mutual interaction. Hence it is not surprising that the intensive development of forcedflow column liquid chromatography (high-performance liquid chromatography, HPLC) as originally potential planar layer version of HPLC entailed the need for the fundamental renewal of the most popular planar layer liquid chromatographic technique, TLC. HPTLC is based on the use of fine particle chromatoplates with narrow particle size distribution of adsorbent and is carried out with capillary-driven separation and sophisticated instrumentation [1]. However, the greatly increased developing time on a fine particle adsorbent layer (quadratic law exists concerning the front migration distance against the time [2]) made it necessary to employ forced mobile phase flow generating or at least approaching the optimum linear velocity to yield the highest efficiency of separation allowed by the layer adsorbent bed characteristic.
