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Impurity Reference Standards

API Reference Standards

Characterised API working standards for assay, identification and routine QC testing, supplied with full analytical data packages.
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Every assay needs a reference of the parent drug, and using a scarce official standard for routine work is costly. API working standards fill that gap. This sub-category lists characterised samples of active substances, such as Abacavir, Abemaciclib, Abiraterone Acetate, Acalabrutinib WS, Aceclofenac WS and Acitretin, for use in day-to-day testing.

Laboratories usually qualify a working standard against the official primary reference before putting it into use. That makes characterisation data essential. Each standard comes with HPLC purity, identity confirmation by NMR, MS and IR, and, where relevant, water content and residual solvents, so that an assigned potency can be calculated.

Standards are supplied in sealed vials in quantities suited to repeated use, typically 100 mg to several grams. Store them as instructed and requalify according to your SOP. If you also need impurity standards for the same drug, search by API name to see related compounds together.

API Reference Standards: questions buyers ask

How is a working standard qualified against a primary standard?
The working standard is assayed against the official reference using a validated method, usually in replicate, to assign its potency. Identity is confirmed by spectroscopy or chromatography. The results are documented, and the standard is given a retest date. Your SOP should define the number of replicates and acceptance criteria.
What does WS mean in a product name?
WS stands for working standard. It indicates a characterised material intended for routine analytical use rather than official pharmacopoeial reference status. The COA provides the data you need to qualify it against your primary reference and to use it in assays, identification tests and system suitability checks.
How often should a working standard be requalified?
Retest intervals are set by your quality system, often annually, and depend on stability data for the compound. Hygroscopic or unstable APIs may need shorter intervals. Store the standard under the stated conditions and record each opening, which supports the case for its continued use.

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