Thin-layer chromatography hyphenated techniques

Cserhati, T. Forgacs, E. Hyphenated techniques in thin layer chromatography. J. AOAC Int. 1998, 81, 329-332. 

Cyclodextrins were used for the modification of such chromatographic techniques as gas chromatography, classical liquid chromatography, high performance liquid chromatography, thin layer chromatography and many hyphenated techniques. Since in the study of enantiomeric composition of monoterpenes gas chromatography modified with cyclodextrins is the main analytical tool, this method will be more widely discussed later on. 

Thin layer chromatography (TLC), also known as planar chromatography, is an invaluable method used in chemistry and biochemistry, complementary to HPLC while having its own specificity. Although these two methods are applied differently, the principle of separation and the nature of the phases remain the same. Cheap and sensitive, this technique that is simple to use, can be automated. It has become essential principally since it is possible to undertake several separations in parallel. The development of automatic applicators and densitometers have led to nano-TLC, also called HPTLC, a highly sensitive technique which can be hyphenated with mass spectrometry. 

Many FT-IR spectrometers have external ports for optical coupling to dedicated accessories. The IR radiation is conveniently directed to/from the external ports by computer-controlled flip mirrors. A large variety of accessories, like an IR microscope, interfaces for gas chromatography (GC/FT-IR), liquid chromatography (HPLC/FT-IR), thin layer chromatography FT-IR (TLC/FT-IR), etc., is commercially available. This type of method combination is usually called a hyphenated technique. FTIR spectrometers can even be supplemented by a FT-Raman accessory. The versatile combination of FT-IR spectrometers with other instruments has substantially contributed to their abundance in most analytical laboratories. 

Srivastava, M.M. 2011. An overview of HPTLC A modern analytical technique with excellent potential for automation, optimization, hyphenation, and multidimensional applications. In Srivastava, M. (Ed.), High Performance Thin Layer Chromatography (HPTLC), Springer, Heidelberg, Germany, pp. 3—26, Chapter 1. 

Hyphenated instruments consist of an inlet that separates and preconcentrates analytes prior to their introduction into an integral detector. A hyphen can be used to separate the two components when the name is written in abbreviated form—for example, GC-MS. The separation module is the GC and the detection module is the MS. As hyphenated instruments became more common, the hyphen often was dropped, and that is the convention used in this book (i.e., GCMS rather than GC-MS). Separations alone, such as in thin layer chromatography, are not instrumental methods in the traditional sense, but mating a separation technique to a detector creates an instrument that is capable of what is called a hyphenated technique. The basis of most separation modules is selective partitioning, a topic discussed in the previous chapter. However, there is a group of hyphenated instruments in which separation is achieved with electrochemical methods, an increasingly important topic in forensic chemistry. 

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