LCGC The Peak - June 2008 - (Page 20)

20 THE PEAK JUNE 2008 Table I: Results of effective automated method screening and subsequent optimization Used 1200 Series Configuration Automated Method Development System Standard Column and Valving Configuration Conditions as above Standard Configuration Optimum Conditions Peak Width of First Peak (min) Peak Width of Second Peak (min) Resolution, Main Peak Resolution, Last Peak 0.0150 0.0152 1.67 3.63 0.0147 0.0154 1.98 3.65 0.0167 0.0169 2.81 4.32 Method Screening was done on the Agilent 1200 Series Method Development System. The developed method was transferred to a standard 1200 Series Rapid Resolution System and optimized for final routine use. to be separated have for the column matrix, and k is the degree of interaction between the compounds to be separated and the stationary phase. As can be seen in Figure 2, beyond a certain minimal value, the magnitude of k does not appreciably affect resolution — the compounds either interact with the stationary phase or not. Resolution obviously increases with the number of theoretical plates (N), but the parameter that has the most impact on resolution is , the differential affinity between the compounds being separated, for the stationary phase. Given the impact of on resolution, method screening experiments should be designed to assure that a sufficient number of orthogonal column packings is evaluated in order to increase the probability of finding a packing that will provide maximum selec- tivity. For example, UHPLC-type packing materials are now available with a wide range of stationary phases and the superficially porous particles are expanding as they are being introduced. All should be carefully considered during methods screening planning. While theoretical plates (N) have less of an impact on resolution than selectivity, the new superficially porous silica packings provide such rapid separations at standard operating pressures that they can be put together in series to provide very high plate numbers ( 100,000 plates), while still allowing very rapid separations (2). Once screening has identified some promising methods, the next step is to optimize them for highest resolution with representative samples, within the run time parameters required by the workflow of the laboratory. Optimal separation conditions

Table of Contents Feed for the Digital Edition of LCGC The Peak - June 2008

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

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.