Unlike the colorimetric process, this method is less sensitive and requires higher protein concentrations and should thus be used with pure protein solutions. In addition to the direct absorbance display, evaluation is possible with the BioPhotometer via the Warburg formula or via standard. Protein samples often consist of a complex mixture of many different proteins. The quantitative detection of the protein content is usually achieved on the basis of the reactions shown by functional groups of the proteins to dye-forming reagents. The intensity of the dye correlates directly with the concentration of the reacting groups and can be measured exactly.
Specialist literature contains a multitude of modifications for the Lowry assay.
The principal target is to reduce the high susceptibility to interference. In comparison to the pure Biuret assay, the sensitivity of this assay has greatly increased. However, the Lowry method is adversely affected by a wide range of non-proteins. Additives such as EDTA, ammonia sulfate or Triton X-100 in particular are incompatible with the test. This test represents a highly regarded alternative to the Lowry assay.