Normalized peak distribution uniformity metrics for chromatographic evaluation

Peak distribution uniformity (DU) has been introduced as a dimensionless descriptor to characterize the global distribution of chromatographic peaks across the elution window and to complement resolution-based separation metrics. However, the original DU formulation may assume negative values in chromatograms exhibiting pronounced peak clustering, even when all peak pairs remain baseline-resolved, thereby limiting its interpretability and practical use in composite quality metrics. In this study, the behavior of the original DU definition is critically examined using simulated chromatograms, and two revised DU formulations are proposed. Both revised metrics are based on the statistical dispersion of inter-peak spacing and ensure that the metric remains within a suitable interval [0,1]. Their numerical behavior is evaluated using representative peak distributions and sensitivity analyses in model peak systems of varying complexity. The results demonstrate that the revised DU formulations have continuous, bounded, and physically meaningful behavior across a wide range of peak-clustering scenarios. Note that DU is one of the parameters proposed to calculate the overall quality of a separation (SQF).