Modified resolution factor for asymmetrical peaks in chromatographic separation

The quality of separation is measured by resolution factor (R-s) between adjacent peaks. The current United States Pharmacopeia (USP) method for R-s calculation assumes symmetrical peak shapes. In practice, perfectly symmetrical peaks are rarely encountered. The goal of this study was to correct the inaccuracy due to peak asymmetry by using a new formula for R-s calculation. Peak tailing factor was incorporated into the formula for the calculation of R-s to correct for the peak asymmetry. The resulting modified formula was compared with USP formula using simulated peaks and actual peaks. Through mathematical derivation, the modified R-s was expressed as: R = [2(t(2) + W-2/2(1-1/TF2) -t(1)-W-1/2(1-1/TF1))]/W-1 + W-2 where t(1) and t(2) are the retention times of two peaks, W-1 and W-2 are peak widths at baseline, TF1 and TF2 are USP tailing factors. All parameters used in the formula are available from commercial data analysis software. Comparisons of modified R-s to USP R-s showed that the modified R-s provided a more accurate measure of peak separation at the baseline level. (C) 2003 Elsevier B.V. All rights reserved.