Testing

Know what you’re researching.

Analytical documentation is only as useful as a reader’s ability to interpret it. This page explains what the common methods measure, what they establish, and where their limits are.

Methods

Two measurements, two different questions.

Chromatography describes how much. Mass spectrometry describes what. Neither answers the other's question, which is why documentation generally carries both.

High-Performance Liquid Chromatography

HPLC

HPLC separates the components of a sample by passing it through a column in a liquid stream. Components that interact more strongly with the column material move more slowly, so substances that entered together emerge at different times.

The output is a chromatogram in which each detected component appears as a peak. Purity is calculated from peak areas: the principal peak's area divided by the total area of all integrated peaks. The result is a relative measure of what the detector registered, under the conditions of that run.

Mass Spectrometry

Mass spectrometry converts molecules into ions and separates them by mass-to-charge ratio. Because a peptide's mass follows from its amino acid composition, a measured mass can be compared against the value calculated from the intended sequence.

A match within the instrument's tolerance is meaningful evidence that the material is the intended compound. It is evidence about composition rather than about the order of residues, which is why identity work sometimes extends to fragmenting an ion and measuring the pieces.

Vocabulary

What the terms mean.

Identity testing

Identity testing asks whether the material is the compound it is said to be. Mass spectrometry is the usual method, because the property it measures follows directly from the molecule's composition.

Purity testing

Purity testing asks what proportion of the material is that compound rather than something closely related to it. Chromatographic purity is reported as a percentage of detected peak area and describes the sample tested, not the compound in general.

Lot numbers

A lot number identifies a specific quantity of material produced under one set of conditions. It is the link between a container in a laboratory and the records describing what is in it.

Analytical documentation

A document reporting results should name the lot, the date, the method, and who performed the analysis. Results without methods cannot be interpreted, and results without a lot number cannot be traced to anything.

These descriptions are general and educational. They describe what the methods do, not what has been performed on any particular material. A test is only reported on this site when documentation exists for the lot in question.

Search Your Lot

Enter the lot number printed on the container to retrieve the analytical documentation published for that lot.

Demo data, not production data. Sample records for interface review: ,

Read the underlying concepts.

The research library covers purity, chromatography, mass spectrometry, and how to read a certificate of analysis.

Research Library View Compounds