Utilization of keratin or sericin-based composite in detection of free chlorine in water

Contaminated drinking water in many parts of the world causes acute health dilemma. An easily applicable method to detect this invisible hazard in domestic tap water is of prime importance. In this investigation we developed a spectro-photometric quantitative method for detection of free chlorine in domestic tap water using protein-based analytical stripes. Two renewable proteins; namely keratin and sericin were extracted from waste materials (coarse wool fleece and raw natural silk) and supported on polyvinyl alcohol (PVA) matrix. The formed protein/PVA composite was used as a hosting material for starch/potassium iodide reagent which liberates iodine upon interaction with free chlorine in water. The liberated iodine generates a measurable bluish colored complex with starch. Detection of chlorine in water was conducted in presence and absence of possible interfering moieties; Viz. elemental bromine as well as bromide and fluoride ions. Amino acid analysis, gel filtration chromatography and Liquid chromatography-mass spectrometry monitored the alteration in the chemical composition of the extracted proteins. The proper method of storage and usage of the proposed analytical stripes was adopted by measuring the solubility of the prepared protein-based composite in water, alkali, and urea-bisulphite solution. The ability of the said composite to withstand deterioration from bacteria was also assessed. Scanning electron microscopy was used to study the surface characteristic of the prepared composites. The proposed stripes are convenient to detect low range levels of free chlorine especially for drinking water or pools below to 4 ppm. (C) 2019 Published by Elsevier B.V.