A Low-Cost LED-LDR Portable Colorimeter-Multimeter (LED-LDR PCM) for Analytical Laboratories in Iraq: An Educational of Deviation from the Beer-Lambert Law and Green Chemistry Approach

A new, low-cost LED-LDR Portable Colorimeter-Multimeter (LED-LDR PCM) was developed as an educational tool for undergraduate chemistry students. This device constructed from inexpensive and available components in the Iraqi markets. These included a multimeter, a white LED light source, a light dependent resistor (LDR), a battery, and a sample cell (cuvette). This device serves as platform for teaching essential principles of the systematic deviations from the Beer-Lambert law with polychromatic LED sources, build calibration curves, and teaching self-filtering effect phenomenon. The LED-LDR PCM device showed a high accuracy and precision in the determination of methyl red dye in tap water samples, with RSD% values from 0.791% to 3.076% and recovery values ranging from 99.131% to 101.562%. The performance of the educational LED-LDR PCM device was evaluated using greenness and Whiteness assessment tools, such as GAPI, MoGAPI, CaFRI, and the Multi-Color Assessment (MA) Tool. A comparative analysis against reported methods revealed that the educational LED-LDR PCM device is more sustainable and environmentally friendly, with a high overall Whiteness score of 66.9%, showed the scores of reported methods. This project highlights a new direction for the development of simple, cost-effective analytical devices that are ideal for educational purposes analytical devices and aligned with the principles of green analytical chemistry.