Chromatography Focus
Liquid-Liquid Chromatography Instrumentation for Laboratory Preparative & Process Chemistry
Liquid-Liquid Chromatography (L-LC) Instrumentation, also referred to as Counter Current Chromatography (CCC, HSCCC, HPCCC), and Centrifugal Partition Chromatography (CPC), designs have existed for 60 years. Solid-Liquid Chromatography (S-LC) techniques include Open Tubular, Flash, MPLC and HPLC also have an extensive history. For the vast majority of applications both L-LC and S-LC have a stationary and a mobile phase. With S-LC the stationary phase is often a liquid, immobilised by bonding onto a solid phase. In L-LC over 99.9% of published applications have one liquid phase stationary, with immobilisation of the stationary liquid phase by the instrument’s design operating procedures. S-LC and L-LC therefore have many fundamental similarities. Discussed here are the similarities/differences and significant inter-compatibilities of L-LC and S-LC.
INTRODUCTION
The use of CCC nomenclature has lead to many decades of confusion in the mode of operation. Non L-LC chromatographers consider a ‘Counter Current’ mode would involve two liquids moving in different directions. With L-LC/CCC despite the fact they can be used with liquids moving in two opposing directions, in reality for 99.9+% of usage, one phase is stationary and one phase is mobile. The International CCC Committee recently redefined CCC/HSCCC/HPCCC as hydrodynamic CCC and sun/droplet CPC as hydrostatic CCC whilst acknowledging all were Centrifugal Partition Chromatographs (CPC). Maybe this does not resolve the fundamental historic nomenclature confusions? Therefore in this publication, this science is referred to predominately as L-LC, rather than CCC or CPC. Planetary CCC, HSCCC and HPCCC will be described as hydrodynamic L-LC and sun or droplet CPC as hydrostatic L-LC
There are very many fundamentally different modes of L-LC Instrumentation design [1]. Whilst L-LC Instrument designers will discuss amongst themselves that different L-LC concepts may show total incompatibility with other L-LC concepts, regarding selection of resolving biphasic solvents for the same target/matrix, this has been rarely published [2].
Author Details:
Brown, Leslie & Luu, Trinh Anh of AECS-QuikPrep Ltd, PO Box 80, Bridgend, S. Wales, CF31 4XZ, UK. Email:
aecs@gmx.com Web:
www.ccc4labprep.com
The above can even be applied within a single manufacturer’s HPCCC or CPC product range, if the manufacturer varies key L-LC design factors. The more key design factors varied within a single manufacturer’s HPCCC or CPC product range, the greater the likelihood of failure during Process Scale-up and greater the likelihood of failure in transfer of biphasic solvent choice between different L-LC instrumentation design concepts.
Modular rationalisation of L-LC design such as in the Quattro CCC™ and Partitron CPC™ [2] can reduce the problems of scale- up to make them no more difficult than in S-LC. Modular design allows the massive
benefits of L-LC to be explored logically. These benefits include, high sample loading (5 to 15% of utilised L-LC volume, typically a range of 5 to 40g injection, with average closer to 10g per 1000ml capacity for a Quattro L-LC™), reduced solvent usage (typically saving half to tenth solvent requirement to prepare same target mass in same matrix as S-LC), no irreversible ‘on-column’ adsorption or degradation, no expensive solid phase to poison, each L-LC run can be from infinitely polar to infinitely non polar or visa versa.
The key design factors in hydrodynamic L-LC are sun & planet radii, beta values (even allowing for speed compensation to maintain constant ‘G’), rotation speed, coil-winding technique, tubing bore etc. For hydrostatic L-LC the key design parameters are chamber shape/insertions/ volume, sun radii and rotation speed.
As previously discussed the more key design factors are changed, the percentage success of process scale-up and cross compatibility between fundamentally different L-LC design modes radically reduces. This factor has to date, not historically been reported in relationship to its percentage occurrence. Disproportionate reporting of successful scale-up/cross compatibility of method transfer of CCC/CPC with different key design modes has led, and continues to lead to distortion of fundamental truths. On occasions it may cause disillusionment of new L-LC users who are unable to reproduce published methods on instrumentation from same or different manufacturers, when the instrument has different key L-LC design modes. Examples of a more realistic situation for scale-up and cross correlation of CCC/CPC, to try to redress the historically bias publications, will be given in the Discussion.
Let us consider S-LC and L-LC from a fundamental chemical/ chromatographic perspective. Given that stationary phase in S-LC is often an immobilised liquid, which has been immobilised by bonding to a solid substrate, it could be considered the only
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