An introduction to the metrics generated.
ChromaAnalyzer provides advanced column‑performance assessment based on peer‑reviewed literature. This page introduces the key metrics generated by the Direct Transition Analysis (DTA) and Moment Analysis methods. Collectively, these quantitative indicators enable proactive maintenance, continuous verification, and rigorous quality control of packed columns.
Moment‑analysis metrics, developed by Larson et al. (2003), extract comprehensive column‑integrity diagnostics from routine process data without requiring dedicated tracer injections.
Counts peaks in the first‑derivative trace (dC/dV) exceeding 10 % of the maximum slope. An increase indicates the emergence of multiple flow paths, suggesting early channel formation.
The steepest point on the derivative reflects how sharply the buffer front moves through the bed. Lower values over successive cycles denote increased axial dispersion and loss of efficiency.
First column volume where the normalised signal crosses 5 % (or 95 %). An earlier breakthrough indicates preferential flow paths or voids and therefore a loss of bed integrity.
Integrates the absolute difference between the real transition and an ideal step (Pe → ∞). A rising value denotes increasing axial dispersion resulting from fines, voids, or headspace.
Calculated from the zeroth, first, and second statistical moments to quantify plate height without assuming a Gaussian peak shape. HETPN is sensitive to cracks and other integrity defects that traditional half‑height methods may overlook.
Ratio of trailing to leading half‑widths at 10 % peak height. Values below 1 indicate fronting, while values above 1 indicate tailing, both of which are symptomatic of packing or flow‑distribution issues.
Classical plate‑height calculated at half‑height assuming a symmetric (Gaussian) peak; retained for continuity with traditional pulse tests.
Combines all seven descriptors into a single 0–1 index using weighted pass / partial‑pass / fail logic. Values near 1 indicate a well‑packed, efficient column; a sustained decline warrants investigation before product quality or yield is affected.
Direct Transition Analysis (DTA), introduced by Cui et al. (2018), streamlines column assessment by extracting efficiency and symmetry directly from raw buffer‑transition curves.
The column volume between 5 % and 95 % of the normalised transition. A widening TransWidth signals increased axial dispersion and reduced separation efficiency.
Derived from the average of front‑to‑back width ratios at several thresholds (10–70 %). Deviations from unity quantitatively capture fronting (<1) or tailing (>1).
Key concepts and terminology used in transitional analysis.
Zeroth moment: total area under the peak. First moment: mean residence volume/time. Second moment: variance, indicating peak width.
The rate of change of conductivity with respect to column volume; used to locate inflection points and assess transition sharpness.
Scaling detector data to a common 0–1 range to enable direct comparison between runs collected under differing detector calibrations or buffer conditions.
The longitudinal spreading of solute along the bed; greater dispersion yields broader peaks and reduced resolution.
Dimensionless ratio of convective flow to molecular diffusion. High Pe approximates plug flow; falling Pe indicates increased mixing.
The ideal symmetric bell‑curve peak; deviations (skewed or multi‑modal shapes) may reveal packing imperfections or fouling.
Fronting: rapid rise followed by gradual decline (Af < 1). Tailing: slow rise with extended trailing edge (Af > 1).
The change in mobile‑phase composition (e.g., low‑salt to high‑salt) used as the basis for transitional analysis.
Column volume required for the signal to move from 5 % to 95 %—a direct measure of band broadening.
