The colorimetric method, also known as the spectrophotometric method, is a widely used technique for determining the concentration of humic acids (HA) in a sample. Although it’s one of the oldest methods, it’s not the most accurate because its results can be easily affected by contamination.
The colorimetric test is not accurate because it relies on measuring the absorbance of light by the HA sample extract at a specific wavelength and compares the value to that of a standard at a known concentration. However, it can also detect fulvic acids and possibly other substances, leading to inflated HA concentration values. Additionally, adulterants such as molasses, which absorb light at the test wavelength, can be added to produce artificially high HA concentrations.
In addition, the HA standard that is used during the process, such as HA from Sigma chemical company or another standard, may not accurately represent the HA chemical composition of HA from all sources. This potential misrepresentation further contributes to artificially inflated and inaccurate results when using the colorimetric method.
