Intermittent counter-current extraction-Equilibrium cell model, scaling and an improved bobbin design.

This paper describes an equilibrium cell model for intermittent counter-current extraction that is analytically solved for the first time for continuous sample injection between a pair of columns. The model is compared with practice for injections of a model mixture of compounds on a standard high-performance counter-current chromatography instrument giving good agreement for compound elution order and the times to maximum concentration for the eluted components. An improved design of end fittings for the counter-current chromatography bobbins is described which permits on-column switching of the mobile and stationary phases.

Controlled-cycle pulsed liquid-liquid chromatography. A modified version of Craig's counter-current distribution.

A new liquid-liquid chromatography technique developed from a combination of controlled-cycle operation and a pulsed-mixing technique is suggested and validated. The controlled-cycle pulsed liquid-liquid chromatography (CPLC) system operates without involving a centrifuge and consists, of a series of multistage units, and a method for imparting pulsation motion to the liquids inside the units (the pulsation cycle). This chromatography technique can be considered as an improved continuous form of Craig's counter-current distribution method, or, alternatively, as a form of droplet chromatography with the cycling mode of operation.

Support-free pulsed liquid-liquid chromatography.

A simple technique of support-free liquid-liquid chromatography is suggested that operates without incorporation of a centrifuge. The pulsed chromatography apparatus consists of a stationary coiled tube and a pulsation device to produce reciprocating motion of liquid phases within each individual coil segment. This reciprocating motion generates a centrifugal force field varying in intensity and direction that leads to an improved mixing of the two liquid phases and retains the stationary phase in the coiled tubing.

Analysis of new counter-current chromatography operating modes.

Some novel cyclic operating modes of counter-current chromatography have been suggested. Chromatographic separation processes with two zones of different partition coefficients and with extraction and scrubbing (washing) zones are mathematically described using the eluting counter-current distribution approach. Two possible cyclic modes of dual counter-current chromatography operation, with simultaneous and alternate transfers of the phases, are analyzed.