Chromatography HPTLC , developments

Recent developments in the practice of thin-layer chromatography have resulted in a breakthrough in performance which has led to the expression high performance thin-layer chromatography . These developments have not been the result of any specific advance in instrumentation (as with HPLC), but rather the culmination of improvements in the various operations involved in TLC. The three chief features of HPTLC are summarised below, but for a comprehensive account of the subject the reader is recommended to consult a more specialised text.59... 

The lipids were separated on a high-performance thin-layer chromatography (HPTLC) plate. The developing... 

Since the introduction of commercial precoated plates in the mid-1960s, continual developments with regard to the increase of selectivity and improvement of separation efficiency were pursued [i.e., ready-to-use layers suitable for high-performance thin-layer chromatography (HPTLC), polar and hydrophobic bonded phases, plates with concentrating zones],... 

High performance thin-layer chromatography (HPTLC) has also been used for the determination of carbamate pesticides.Thus, TLC methods provide increased selectivity through silica derivatization, as well as higher analytical precision and sensitivity with high-performance plates. Butz and Stan reported an HPTLC system with automated multiple development (AMD-HPTLC) to screen water samples for pesticides. The method was applied to the determination of 265 pesticides in drinking water spiked with 100 ng/1 of each analyte. 

High-performance silica is used in high-performance thin-layer chromatography (HPTLC). HPTLC differs from normal TLC in that the size of the absorbent (usually silica) is only 5 pm, with a narrow distribution. This enables HPTLC to give better separations compared with TLC, which uses a standard silica, and, moreover, HPTLC requires a smaller sample size and has a lower detection limit compared with conventional TLC. HPTLC plates of varying sizes are commercially available and of late have found considerable applications in the field of lipids. Weins and Hauck (1995), in their survey of TLC, conclude that the use of HPTLC plates increased by 30% over the period 1993-95. An excellent application of HPTLC is illustrated in Fig. 1.1 for the separation of neutral and complex lipids. Yao and Rastetter (1985) have achieved separation of more than 20 lipid classes of tissue lipids on HPTLC plates using four developing solvents. 

The lipids were separated on a high-performance thin-layer chromatography (HPTLC) plate. The developing solvent was a mixture of chloroform, methanol, and 0.2% aqueous CaCl2. Orcinol reagent and Dittmer s reagent were used to detect glycolipids and phospholipids. 

A review of all sorbents used as stationary phases in thin-layer chromatography (TLC) is reported. The specific apphcation field of aU sorbents is described according to tbeir relative chemical physical properties. New materials have been developed for the high-performance thin-layer chromatography (HPTLC) technique to offer both high-efficiency separations and high-sensibility analysis. In particular, sUanized sihca gel bas been extensively used as stationary phase in reversed-phase (RP) chromatography for its hydrophobic properties. 

To improve the separation efficiency in TLC, many different modifications of this chromatographic technique have been developed [3]. The most important is high-performance thin-layer chromatography (HPTLC), which has increased precision by one order of magnitude, lowered analysis time, reduced development distances on the layer, and lowered solvent consumption [4]. These benefits were... 

---