From Thin-Layer Chromatography: A Modern Practical Approach
8 Concentration Zone TLC/HPTLC Plates
The concentration zone concept offers a number of benefits for certain types of analysis. The benefits were first described by Abbott and Thomson in 1965 [77] and elaborated on further in 1969 by Musgrave. [78] The TLC/HPTLC concentration zone plate consists of two different layer sections with a sharply defined borderline. There is no gap in between. The lower zone is used for sample application and covers the full width of the plate up to 25 mm. This lower zone is composed either of kieselguhr or synthetic porous silicon dioxide of medium pore volume, but very high pore diameter (50 000 ) and extremely small internal surface area (less than 1 m 2 g ?1). Kieselguhr being a natural material, mainly composed of silica, and approximately 10% of other metal oxides' can cause variations in chromatographic behaviour. The upper section of the plate is coated with normal silica gel 60 sorbent. Samples are applied as spots or bands to the concentration zone. Usually these are more dilute (typically 5 10 times) than what would be applied to a normal silica gel 60 TLC layer. On elution the analytes of interest migrate at or near the solvent front. On reaching the interface they form a concentrated band. This continues to migrate into the silica gel 60 layer and development continues normally. Although there are obvious advantages to the use of such concentration zone plates such as eliminating the need for precise positioning of...
Products & Services
Topics of Interest
9 HPTLC Pre-coated Plates HPTLC uses the same type of silica gel 60 layers, as in traditional TLC, with a thickness of 0.20 0.25 mm. However, the particle size is much smaller, typically ranging...
2 Preparation of TLC Sheets and Plates 2.1 "Home Made" TLC Plates Before the advent of commercial pre-coated TLC plates, layers of silica gel and of other sorbents (e.g. cellulose or aluminium...
1 Introduction There is no doubt that combining planar chromatography, particularly HPTLC, with spectrophotometric and other chromatographic techniques extends the capabilities of analysis...
1 Introduction Pre-treatment of samples before application to the TLC/HPTLC layer rarely requires more than a few basic steps. The quality of commercially available TLC and HPTLC layers is such that...
1 Introduction Adequate sample preparation and careful application of the sample to the TLC or HPTLC layer is imperative for good chromatographic separations. Frequently poor separations are blamed...
