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Impurity Reference Standards

API Impurities

Process impurities, isomers, degradants and related compounds for thousands of APIs, characterised for method development, validation and QC release.
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API Impurities is the largest single sub-category in the catalogue, covering related compounds for most commercial drug substances. It includes stereoisomers such as (1R,4S)-Sertraline and (3R,5R)-Rosuvastatin, intermediates and by-products like the (R)-Sitagliptin N-Boc-Acid Impurity, enantiomers such as (R)-Zopiclone and (S)-Mirabegron, and diastereomers such as the (2S,4S)-Sacubitril Isomer.

Analysts use these standards to identify unknown peaks, confirm specificity, measure relative response factors and spike validation samples. The questions to ask are whether the structure matches your peak, whether purity is high enough for quantitation, and what data support it. Each standard comes with HPLC purity and structural data from NMR and MS, with IR or other tests where relevant.

Standards are supplied in milligram quantities in sealed amber vials and sent by express courier. If a peak in your chromatogram does not match a listed compound, our team can propose a structure and synthesise it. Browse all impurities for one drug on the impurity standards index.

API Impurities: questions buyers ask

How do I identify which impurity matches an unknown peak?
Compare retention time and UV spectrum with candidate standards run under the same method, then confirm with LC-MS if needed. Consider the synthesis route and degradation pathways of the API to shortlist likely structures. Spiking the sample with a standard and watching the peak grow is a simple confirmation.
What is a relative response factor and how is it measured?
A relative response factor compares the detector response of an impurity with that of the API at the same concentration. It lets you quantify impurities against the API standard instead of each impurity. It is measured by injecting known amounts of both and comparing the slopes of their calibration lines.
Can impurity standards be shipped with the API order?
They can travel together if both are sent by the same mode, but impurity standards normally go by express courier due to their small size and high value. APIs often travel by air or sea cargo. We usually ship standards separately so they reach your lab quickly while the API follows by its own route.

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Paste up to 200 CAS numbers into Bulk CAS lookup, or send one enquiry for everything in your quote list. We reply with price, lead time and documents.

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