Of chromatographic solvents

P. Stepnowski, K.-H. Blotevogel, P. Ganczarek, U. Fischer and B. Jastorff, Total recycling of chromatographic solvents — applied management of methanol and acetonitrile waste. Resource Conserv. Recycl. 35 (2002) 163-175. 

Michulec, M. and W. Wardencki. 2005. Selected aspects of chromatographic solvents residues determination using HS, SPME an SDE techniques for isolation and preconcentration of analytes. Book of abstracts of 11th International Symposium on Separation Sciences, September 12-14, 2005, Pardubice, Czech Republic. 

Karger, B. L., Snyder, L. R., and Eon, C. (1976). An expanded solubility parameter treatment for classification and use of chromatographic solvents and adsorbents. Parameters for dispersion, dipole and hydrogen bonding interactions. J. Chromatogr. 125, 71-88. 

It is clear that as the internal diameter of the column increases, so does the mobile-phase volume, and then the volume of mobile phase that is necessary for any given chromatographic analysis. This affects the cost of the analysis, both directly in increased usage of chromatographic solvents, and also through increased solvent disposal cost. This cost factor is one of the primary reasons driving the interest in small-diameter columns, which will be discussed in more detail shortly. 

Grant, R. (1992) Properties of chromatographic solvents. LC/GC Int 5, 25 (selected data reproduced with permission). 

The ChromAR sheet has several advantages over TLC plates (1) it conforms entirely to the agar surface, making contact complete (2) the adsorbent does not adhere to the agar, therefore no paper need be used to separate the sheet from the agar (3) much lower levels of antibiotic often need to be spotted compared to TLC plates, apparently due to a more efficient transfer of material from sheet to agar and (4) in a number of chromatographic solvent systems development was up to twice as rapid as with TLC plates. 

Note 2. Selection of chromatographic solvent An unknown mixture should be first chromatographed on 20 cm x 5 cm plates with solvent of different polarities to obtain an idea of the polarities of compounds present in the sample and to reduce the possibility of missing any of the sample components. Solvents of low polarity, such a n-hexane, tetrachloroethylene and carbon tetrachloride, cause polar sample constituents to migrate more readily. Solvents of intermediate polarity such as toluene, benzene, chloroform and methyl cellusolve have a greater elutive effect on polar sample components, whereas highly polar solvents such as dioxan, methylene dichloride, ethyl acetate, nitromethane, acetone, lower alcohols and water elute polar sample constituents towards the solvent front, ie. Rf values near unity. Mixtures of 40/60 petroleum spirit and up to 10% (v/v) ethyl acetate are very useful general solvents for the separation of unknown mixtures. 

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