A biochemistry analyser works on the photometric principle: it measures the amount of light absorbed by the reaction solution at a defined wavelength to derive the concentration of the analyte.
The Lambert-Beer law underpins the measurement: absorbance is proportional to the concentration of the solute and to the path length of the solution the light passes through. This allows the analyser to accurately quantify parameters such as glucose, urea, creatinine and liver enzymes.
For stable results, the laboratory must standardise the light source, wavelength filters and cuvettes, and run periodic internal quality control as recommended by the manufacturer.