COMPARATIVE STUDY OF DPD REAGENTS FOR CHLORINE MEASUREMENT IN DRINKING WATER AND DEVELOPMENT OF A JAVASCRIPT INTERPOLATION TOOL

<p><span>Background: Determining chlorine in water ensures safety. Among other methods, the DPD colorimetric method is used. The DPD Method relies on colorimetric reactions to measure free and total chlorine concentration in water samples with pink compound formation. Aims: To perform a comparative chlorine analysis using DPD, assessing reagents from 3 makers and 2 Hach instruments to identify disparities and propose adjustments for more accurate measurements. Methods: Hach High-Range and Low-Range Free chlorine determination procedures were followed. DR300 and POCKET Colorimeter II spectrophotometers were used. Tests were conducted for each DPD manufacturer in low/high ranges and in two HACH devices to determine the chlorine concentrations. Hach was used as the reference; LaMotte and PoliControl compared against it. Statistical analyses were compiled using MS Excel. Results: The tests findings were gathered in Tables 1-5. JavaScript and HTML scripts were created to convert LaMotte and PoliControl outcomes into values equivalent to those of HACH through linear interpolation. Discussion: Various DPD reagents and equipment provided slightly different readings, prompting empirical evaluation of these differences. Adjusting the results to Hach's results was selected as both the reagent and spectrophotometer were from the same brand. Differences in spectrophotometer readings were more pronounced in high-range tests nearing the upper limit of the test. Conclusions: Equipment variations caused minor result differences; DPD reagents are not interchangeable without correlation. The Open-source code developed aided in reducing reading disparities.</span></p>