Book: Automated Multiple Development.
Chapter 4: “Instrumental Thin-Layer Chromatography”.
Edited by Colin F. Pool, Elsevier Science, USA, 2014.
Thin-layer chromatography (TLC) began and still is, at least in part, a manual and modular technique. In column chromatographic techniques, a sample is injected into some sort of apparatus at the head of a colum and the chromatographic separation is registered at another part of the apparatus at the opposite end of the column. In TLC, the sample is put on a plate that has to be moved to another apparatus to be developed, and finally to a further apparatus to record the chromatogram. Application, development, and even detection in the case of colored compounds can be performed with minimal equipment requirements and TLC is, therefore, at least in part, a low-cost technique. Nevertheless, even in these simple cases, TLC results can be quite good. It is not surprising, then, that efforts to improve TLC have focused on a particular step in the process, so we now have different methods of sample application and development systems, and detectors, that can be combined depending on the analytical needs. A completely automate TLC system consists of several instruments that afford almost unattended operation, apart from the need to move the plate from one instrument to another. It is also capable of providing increased reproducibility,separation capability, sensitivity, and many other benefits, but at the same time with an increase in cost. As it is still possible to obtain quite good TLC results at minimal cost, the success of the different instruments developed to improve TLC operation have always been dependent on a not so easy balance between cost and performance. Many good ideas have not survived, or are even awaiting a commercial opportunity to become of general use. One of the most successful additions to TLC in the last decades is an improved development system that balances cost with a series of important benefits in some aspects of the technique. Since Poole [1] wrote a comprehensive review in 1991, automated multiple development (AMD) is no longer a promising technique but a reality that seems to be here to stay, and so it deserves some additional attention. We will try to show its origins, current applications, and posible future.
Thin-layer chromatography (TLC) began and still is, at least in part, a manual and modular technique. In column chromatographic techniques, a sample is injected into some sort of apparatus at the head of a colum and the chromatographic separation is registered at another part of the apparatus at the opposite end of the column. In TLC, the sample is put on a plate that has to be moved to another apparatus to be developed, and finally to a further apparatus to record the chromatogram. Application, development, and even detection in the case of colored compounds can be performed with minimal equipment requirements and TLC is, therefore, at least in part, a low-cost technique. Nevertheless, even in these simple cases, TLC results can be quite good. It is not surprising, then, that efforts to improve TLC have focused on a particular step in the process, so we now have different methods of sample application and development systems, and detectors, that can be combined depending on the analytical needs. A completely automate TLC system consists of several instruments that afford almost unattended operation, apart from the need to move the plate from one instrument to another. It is also capable of providing increased reproducibility,separation capability, sensitivity, and many other benefits, but at the same time with an increase in cost. As it is still possible to obtain quite good TLC results at minimal cost, the success of the different instruments developed to improve TLC operation have always been dependent on a not so easy balance between cost and performance. Many good ideas have not survived, or are even awaiting a commercial opportunity to become of general use. One of the most successful additions to TLC in the last decades is an improved development system that balances cost with a series of important benefits in some aspects of the technique. Since Poole [1] wrote a comprehensive review in 1991, automated multiple development (AMD) is no longer a promising technique but a reality that seems to be here to stay, and so it deserves some additional attention. We will try to show its origins, current applications, and posible future.