What is a potential source of error in the colorimetric method for measuring Pi?

In the colorimetric method for measuring inorganic phosphate (Pi), the accurate determination of Pi concentration can be significantly affected by the presence of proteins in the sample. When proteins precipitate, they can interfere with the reaction involved in the colorimetric analysis, potentially leading to inaccurate measurements. Precipitation of proteins may result in a reduced concentration of the analyte in the supernatant or cause non-specific color formation, which skews the results.

This effect is particularly significant in colorimetric assays, where the intensity of the color produced is proportional to the concentration of the analyte. The presence of precipitated proteins can reduce the amount of free phosphate in solution, thus leading to a lower recorded concentration than what is truly present in the sample.

Addressing protein interference is crucial for ensuring the reliability and accuracy of results when using the colorimetric method for phosphate measurement. Different techniques, such as filtration or centrifugation, may be used to minimize or eliminate this source of error before performing the assay.