Photocolorimeter: The Unassuming Workhorse in the Laboratory Setup

Photocolorimeter: The Unassuming Workhorse in the Laboratory Setup

If you step into most biochemistry, pathology, and water testing labs, chances are that you will spot a photocolorimeter occupying one corner of the bench among other sophisticated instruments. However, this seemingly ordinary machine is often the instrument that does the hard work in the measurement of glucose, proteins, and in water quality testing. Having written many articles on laboratory instrumentation and having interacted with laboratory technicians who operate the instruments on a daily basis, I have realized that most novices do not understand the real use of a photocolorimeter and misuse it or underestimate its accuracy.

Functions of a Photocolorimeter

The main function of such an apparatus is measuring the concentration of a solute in a solution based on the amount of light of particular wavelength that gets absorbed by the solution. The light source directs a beam of light through a solution that is colored and a photodetector on the other end of the solution detects the amount of light that goes through the solution. With increased color intensity, there is more absorption of light. The basis of colorimetry principle lies on the Beer-Lambert law and it is used in calculating the concentration. Unlike a UV visible spectrophotometer that involves scanning through many wavelengths, filters are used in a photocolorimeter hence making it cheaper and effective when carrying out tests.

Difference Between Photoelectric Colorimeter and Traditional Visual Comparator

Earlier laboratories used visual color comparator, in which an operator compared the color of the sample to that of the reference chart visually. This technique was prone to error due to variability in human judgement as well as in light sources. Photoelectric colorimeter used the same concept, but this time a photoelectric cell was used, turning the light into absorbance or transmittance values. It is the reason for colorimeters still being widely used for clinical analysis, food quality control, and environmental monitoring.

Popular Applications of a Photocolorimeter in the Laboratory

Clinics need it for the analysis of glucose, hemoglobin, and cholesterol because it is based on color development when reacted with a reagent. Water treatment laboratories make use of it for assays of chlorine, iron, and turbidity measurements because it is necessary for checking the water supply. Food and beverage industries also use a colorimeter in the lab for testing food and beverages, whose colors are essential to ensure their quality.

Knowledge About the Principle of Operation of the Photocolorimeter Prior to Purchase

It is always better to know how the photocolorimeter works prior to making the purchase and not just compare the technical characteristics on paper. Pay attention to the wavelength range supported by the filters, since that will determine what kind of tests can be done using the device. Consider the issue of digital versus analog displays, since digital displays eliminate errors that may occur while reading from the needle-type analog meters which some old models of the devices feature. The choice of devices with fast operation speed and easy access to the cuvette holder is especially important if you have to work with many samples per day.

Bionics Scientific Technologies is a leading laboratory and scientific equipment manufacturer based in India