Skip to content

Glossary

Terms beginning with I

13 of 238 glossary terms.

Ion-pair chromatography: Adding an amphiphilic counter-ion to the mobile phase so a charged analyte forms a neutral pair with enough hydrophobic character to be retained on C18.
Isocratic: Constant mobile-phase composition throughout the run. Simpler, and unsuitable for samples spanning a wide hydrophobicity range.
Identification threshold: The level above which an impurity must be structurally identified rather than merely quantified. ICH Q3A sets it by daily dose.
Ion suppression: Reduction in analyte ionisation caused by a co-eluting species or a mobile-phase additive. Trifluoroacetic acid is a strong suppressor.
Isotope pattern: The set of peaks arising from natural isotopic variants of a molecule. Its spacing gives the charge state directly: 1/z daltons.
Ion chromatography: Separation of ions on an ion-exchange column with suppressed conductivity detection. The reference technique for counter-ion quantification.
ICP-MS: Inductively coupled plasma mass spectrometry. Elemental analysis. Required for metal-complexed peptides and for elemental impurity profiles.
Isoaspartate: The rearranged product of deamidation via a succinimide intermediate. Mass-identical to aspartate-containing peptide.
Impurity fingerprint: The vector of named impurities and their levels in a lot. Characteristic of one manufacturing run; used by the index to identify shared bulks.
Inhibition/enhancement control: A spike of standard endotoxin added to the sample to show the matrix does not interfere. Must recover at 50–200 % or the result is invalid.
Interquartile range (IQR): The difference between the 75th and 25th percentiles. The index's preferred spread statistic because purity distributions are left-skewed.
Intermediate precision: Precision across days, analysts and instruments within one laboratory. Wider than repeatability and more realistic.
Index reference method RG-2: The index's nominated reverse-phase method: C18 2.6 µm, 0.1 % TFA, 5→65 % acetonitrile over 30 min at 40 °C, 214 nm. All retention windows are stated against it.