A colorimeter is a relatively simple sensor device consisting of a light source, sample (cuvette)
holder, light intensity sensor and means of controlling the light source and integrating transmitted light
intensity. Incident light is generally filtered allowing only a narrow band near the absorbance peak for
a given dissolved species. The method requires a blank solution for calibration (zero) and reports results
in absorbance units, transmittance or applies the Beer-Lambert law to report results as concentration [21].
Colorimetric methods are used widely in researchand industry, including investigating food during
storage such as bread [22], chocolate [23] and milk [24]. Colorimeters are used to monitor the levels of
nitrates, phosphates, metals and other compounds present in effluent from the manufacture of paper
and other commercial goods [25,26]. They have also traditionally been used to estimate the population
density of protozoa in a culture and more recently by the medical community to measure the UV
radiation exposure of children though skin color changes and to study the aging of bruises [27–29].
One of the more popular applications of a colorimeter is measuring the chemical oxygen demand
(COD) for estimating the organic content of waste waters. COD is also a measure included in some
water quality indices (WQI) [30]. There are sophisticated and expensive methods to determine COD
with high accuracy [31,32], but often at high cost and increased production of waste from the analyses