Modern Thin-Layer Chromatography [antikvár]

Foreword At present, chromatography is the premier method for separating organic and biological mixtures. The development of liquid chromatography (LC) is in no small measure the major factor in this trend. Relative to gas chromatography (GC), there are few restrictions with regard to the sample type that can be separated by LC. The range of LC systems runs from low-molecular-weight up to large polymeric species, which can be chromatographed on LC systems, at room temperature or at subambient operation, if required. In addition, the efficiency and especially the ability to manipulate molecular interactions for high selectivity has made high-performance liquid chromatography (HPLC) the significant method it is today. There are two ways to operate LC systems: column and open-bed or thin-layer chromatography (TLC), the latter being the subject of this book. Both approaches contain the power of selectivity manipulation, and indeed they can often be used in conjunction with one another. For example, scouting for appropriate mobile phase conditions (as well as the proper stationary phase) can be rapidly and conveniently accomplished on TLC plates followed by column operation. Relative to column LC, the beauty of TLC lies in its simplicity and inexpensive operation. Methodology has advanced to the point that it is relatively error-proof and can be operated by individuals with low technical training. An important area of application is the screening of samples for qualitative determination of specific species, for example, drugs in urine or purity check of a synthetic mixture. TLC has several other important advantages over column operation. First, the overall throughput can be higher since many samples can be spotted on individual plates and developed simultaneously. In column operation only one sample can be run at a time. (In the boxcar configuration, however, several samples can be run simul-