Width Based Characterization of Chromatographic Peaks: Beyond Height and Area.

The preceding paper (Anal. Chem. 2017, 10.1021/acs.analchem.6b04857) introduced width-based quantitation (WBQ). The present paper focuses on (1) situations where WBQ is effective while height/area-based linear calibrations fail, e.g., when (a) the detector is in a nonlinear response region, (b) the detector/data system is saturated, causing clipping/truncation of the signal, or (c) the detector signal is not a single-valued function of concentration, as when a fluorescence signal goes into the self-quenched domain. (2) Utilization of WBQ in postcolumn reagent addition methods where the reagent produces a significant detector background. WBQ can minimize added reagent without sacrificing the upper determination limit; a limited reagent amount truncates peaks from high analyte concentrations but does not hamper WBQ at a low height. (3) A description of peak asymmetry via leading/trailing half-widths vs relative height (fraction of maximum height) plots. (4) A holistic description of chromatographic peaks through six parameters describing the two independent generalized Gaussian distributions that underlie the WBQ chromatographic peak model. (5) Characterization of shape by widths at multiple heights and shape-based impurity detection.