5. Check the specificity of your method

Analytical specificity is the ability of a method to determine only the target marker. It verifies that the method measures only the desired analyte and not a sum of products (analyte C + interferents X ). It is studied in the laboratory by means of an overload test (or dosed addition method), which reveals a systematic error induced by the matrix, or by a dilution test. To do this, simply add a known concentration ( C ) of the analyte to an unknown sample ( X + C ) and plot the slope. If the slope passes close to the origin, the absence of interference is assumed.