Chromatography is the most frequently used analytical technique in pharmaceutical analysis. The HPLC conditions such as solvents composition, choice of detector, and column selection, are functions of the molecular structure of the target compound and the sample matrix. Most pharmaceutical compounds are organic acid or amine substances containing UV absorbing chromospheres in their structures, and are amenable to HPLC by UV detection.

General Procedure for Potency Determination:

HPLC is a robust technique for pharmaceutical analysis, and has been employed for potency assay, purity determination, stability study, metabolite identification and determination. Analysis of drug in formulation has potential interference from preservatives, colorants, and degradation products of the active components. Some formulations contain more than one active component, and their analysis can be a challenge.

Potency assay for active pharmaceutical ingredient (API) in formulation is normally performed using an external standard method, where a reference standard of the drug is used to calibrate the instrument for quantitative measurement. According to the United States Pharmacopeia (USP) and the Food and Drug Administration (FDA), the analytical system should be calibrated using USP-grade reference material prepared at ± 20-25 percent of the expected concentration of the target analyte in the sample preparation.

The relative difference in assayed amount and labeled amount is expressed as a percentage of expected concentration for the target analyte on the Certificate of Analysis (COA). This value is specified in the USP monograph for the particular formulation, or ± 10 percent (i.e., 90-110 percent of label concentration). When potency is outside of the specified range (or OOS), ARL will conduct OOS investigation to determine the basis for the observed OOS result.