LCGC The Peak - June 2008 - (Page 21)

JUNE 2008 THE PEAK 21 are a function of the physics and chemistry of the separation system (3), and both should be given serious consideration during the optimization phase. Optimizing Parameters compared with the kinetics of mass transport in the column can cause band spreading. This interaction can complicate attempts to optimize methods, but rapid methods screening and optimization procedures can help overcome this obstacle. Automated Methods Development Physical parameters primarily determine the kinetics of separation and include factors such as particle size, porosity, column dimensions, flow rates, and temperature. The superficially porous packings are tailored to drive very fast separation times (1 min) due to the short diffusion path, and the low backpressures created by the larger particle size. Chemical properties have the greatest impact on the thermodynamics of the separation process, thus affecting retention and selectivity for the compounds being separated. Because selectivity has the greatest impact on resolution, optimization efforts should focus on the chemical properties that influence the separation. Appropriate mobile phases should be selected to complement the chemical properties of the stationary phase and the solutes being separated. Very low or high pH may be required to enable the solutes to interact effectively with the stationary phase, thus requiring column packings that can withstand these extreme conditions. The temperature also can affect thermodynamics, and is again an important parameter to be considered during optimization. The kinetics and thermodyanamics of the separation also can be strongly interdependent. For example, slow chemical equilibria In most laboratories, resources and knowledge are focused on achieving day-to-day high-quality results, rather than optimizing methodology systematically. If methods development cannot be done very quickly and efficiently, the laboratory manager cannot justify the time and expense required to adopt the new rapid resolution capabilities. Therefore, a modular methods development system that does not require a significant capital investment or expert operator skills and that provides rapid design, tailoring, and review of methods is required to provide fast and inexpensive transition to the new methods. Comprehensive methods development solutions that eliminate the need for manual column and solvent changing between methods can greatly reduce the time required to develop new, highly efficient methods (Figure 3). Such a system should allow for the selection of a large number of different solvent pairs, as well as multiple organic solvents, and should accommodate several columns, each of which can be held at a different temperature, simultaneously. Most importantly, the methods development solution should be modular and require a modest investment. This kind of

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LCGC The Peak - June 2008 The Value of Human Interaction Keeps Pittcon "Live" and Well Screening and Optimizing High-Speed, High Resoultion HPLC Methods in the "Lean Laboratory" The 56th Annual ASMS Conference: A Review Industry News Events Education

LCGC The Peak - June 2008

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