Chromatogram¶

Definition¶

A chromatogram is a graphical representation of the detector signal over time during an HPLC analysis. It shows the separation of sample components as peaks plotted against retention time.

Overview¶

The chromatogram (often called the "HPLC trace") is the primary visual output of an HPLC analysis. It provides a fingerprint of the sample's purity profile — a clean chromatogram with a single major peak indicates high purity, while multiple additional peaks indicate the presence of impurities.

Technical Explanation¶

Reading a Chromatogram: - X-axis: Retention time (minutes) - Y-axis: Detector response (absorbance units at UV wavelength) - Each peak represents a separated compound - Peak area correlates with quantity (proportional detection) - Peak shape indicates column performance and compound behavior

Key Chromatogram Features: - Main peak: The target peptide - Impurity peaks: Additional compounds (identified by RRT) - Baseline: The detector signal between peaks (should be stable) - Tailing factor: Measure of peak symmetry (should be ≤2.0) - Resolution: Separation between adjacent peaks (should be ≥1.5)

Importance in Peptide Documentation¶

The HPLC chromatogram is included with each Certificate of Analysis as visual evidence of product quality. It allows researchers to independently assess the purity profile, not just rely on numerical purity values.

Frequently Asked Questions¶

Q: How do I assess purity from a chromatogram? A: Look for a single dominant peak. Any additional peaks (shoulders, small bumps, baseline separations) indicate impurities. Compare with reference chromatograms from trusted sources.

Q: What indicates a good quality HPLC analysis? A: Good baseline stability, sharp symmetrical main peak, baseline separation from impurities (>1.5 resolution), and consistent retention time with established specifications.