What is a highly specific test used to determine protein concentration through antigen-antibody interaction?

The chosen answer, ELISA (Enzyme-Linked Immunosorbent Assay), is highly specific for determining protein concentration due to its reliance on antigen-antibody interactions. In an ELISA, a specific antigen is attached to a solid surface, and a sample containing potential antibodies is applied. If the antibodies specific to the antigen are present in the sample, they will bind to the antigen. This binding can then be detected and quantified using an enzyme-linked secondary antibody and a substrate that produces a measurable signal, typically a color change.

This specificity is particularly useful in applications such as diagnostics, where accurate protein quantification is crucial. The assay can be designed to target a specific protein among a mixture, enabling precise measurements in various biological samples.

In contrast, potency assays are generally used to measure the biological activity of a substance rather than specifically quantifying protein concentration. Standard Operating Procedures (SOPs) are guidelines for conducting processes and do not directly relate to quantifying proteins. Batch records document the details of manufacturing processes but do not measure protein concentration like ELISA does. Therefore, ELISA is the most appropriate test for this question as it directly addresses the need for specificity in protein concentration determination through its antigen-antibody interaction mechanism.