There is increasing pressure to increase productivity in chromatography, resulting in the research and development of faster and more efficient methods. However, there are a few factors which limit the speed of chromatography: the number of substances to be separated, the duration of the sample preparation and the speed of the autosampler.
Dissolution as one of the most important chromatographic parameters is crucial in determining how quickly a mixture of substances can be separated. The peaks of the individual substances need a sufficient dissolution and selectivity.
Especially with a large number of substances in a mixture resulting in many peaks to be separated, gas chromatography is the method of choice since the columns have many separation stages. The condition, however, is the fugacity of the substances without them to decompose. This is a limiting factor for many substances.
Especially for charged particles Capillary electrophoresis is a good alternative. However, sample preparation is an additional time burden here. In case autosamplers are used, the capacity of the devices is the limiting factor regarding time requirement. Methods such as UPLC, UHPLC, or capillary electrophoresis are mainly used for the separation of substances that do not require any preparation.
HPLC is the best option if sample preparation is necessary. In order to be able to use all conventional HPLC devices, columns larger than 3 mm in diameter should be renounced. Regarding the method one should choose an isocratic composition of the eluent, since here, among other things, the reconditioning time offers a great time saving potential.
In order to meet the productivity requirements for this method the financial factor should not be neglected. Cheap devices are good as long as they meet all FDA requirements. In addition, the usage of solvent recyclers is another way to reduce costs.
Thin-layer chromatography is a very effective and simple method. Here, more than 10 samples can be easily separated within 15 minutes. The ease of handling thus does not require sample preparation and has low costs. Through the coupling with MS devices, the importance of this method is further emphasized.
In summary, many factors are crucial for deciding upon which method is appropriate. The method with the highest technical standard is not always the most efficient choice in all cases.