Loading
What the peaks mean, why the baseline matters, and how to spot a chromatogram that does not justify the headline purity number.
A chromatogram is a small graph and a large amount of information. If you only look at the headline purity percentage you are missing most of what the analytical chemist was trying to tell you.
The horizontal axis is time in minutes — how long the eluent took to travel through the column. The vertical axis is detector response (typically UV absorbance at 220 nm or 280 nm for peptides). Each peak represents a compound emerging from the column at its characteristic retention time.
A well-resolved peak is approximately Gaussian, narrow, and returns to a clean baseline before the next peak begins. Asymmetry (tailing or fronting) suggests interactions with the column, overloading, or sample-matrix effects.
A flat, low baseline is evidence of a clean run. A drifting or noisy baseline can hide minor peaks that the integration software then fails to report — and those minor peaks are what distinguishes 95% purity from 99.5% purity. Always look for the baseline before believing the headline number.
HPLC purity is computed as the area under the main peak divided by the total area under all integrated peaks. A 99.4% figure means 99.4% of the detected material at the chosen wavelength is the target compound. Two things to keep in mind:
Some patterns suggest the COA is not giving you the full picture:
Snyder L. R., Kirkland J. J., Dolan J. W. · Introduction to Modern Liquid Chromatography (3rd ed.) · Wiley, 2010
Astrel Bio products are sold strictly for in-vitro and animal research purposes. They are not intended for human or veterinary consumption, therapeutic or diagnostic use. Misuse may be unlawful under the UK Human Medicines Regulations 2012. By purchasing, you confirm you are a qualified researcher acquiring these compounds for legitimate research.