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Written by The Clever Chromatographer
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Monday, 18 January 2010 20:20 |
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A new instrument article has reached the presses after its public debut at CCC2008. The article entitled “A new non-synchronous preparative counter-current centrifuge” appears in JCA 1217 p.34. The authors report on results from a specially manufactured CCC instrument that has independent control of the “sun” and “planet” axes. Planetary motion involves rotation of the sun axis, called the axis of revolution, and the planet axes, called the axes of rotation. In the “J-type” instrument, the axes all rotate in the same direction, while in the “I-type” instrument the axis of revolution and the axes of rotation rotate in opposite directions. The two axes may also experience synchronous or non-synchronous rotation. In synchronous rotation, the axes turn at a fixed angular momentum relative to the axis of revolution since the planetary axes are connected by a cog or a pulley to the sun axis. In non-synchronous rotation, the angular momentum of the axes of rotation can be adjusted independently of the axis of revolution. The instrument has allowed the authors to observe the stationary phase retention, K value determination, and resolution of a mixture of three compounds in a heptane/ethyl acetate/methanol/water solvent system. The traditional 1:1 J-type ratio of sun and planet does pretty well but is out-performed by at least one other non-synchronous condition. Interestingly, the K values of the analytes shift somewhat as the conditions are changed, suggesting that the mixing efficiency of the instrument affects their values. This is a very interesting, and anticipated experiment but the practical advantage of having two more parameters to optimize in addition to flow rate, rotation speed, column loading, temperature, etc… has yet to be demonstrated.
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Last Updated on Monday, 18 January 2010 20:25 |
