Skip to main content
U.S. flag

An official website of the United States government


Colorimetric analysis or the measurement of an analyte using light absorbance is a common type of analysis at the NWQL for nutrients and select anions.  Colorimetric analysis or colorimetry is automated at the NWQL using Discrete Automated Analysis and Automated Segmented Flow Analysis.  Colorimetry works by reaction of the analyte (e.g. nitrate or o-phosphate) with various chemicals to produce a colored compound.  The colored compound is then sent to a detector where its light absorbance is measured to determine how much analyte is in the water sample.