An aggregation induced emission based simple and sensitive fluorescence ‘Turn-On’ method for monitoring sodium hexa-meta-phosphate, a food preservative

Abstract

Sodium hexa-meta-phosphate (HMP) is an important quality improver in the food industry. However, an excessive use of HMP not only deteriorates the nutrition value of the food but also causes ailments, such as, skeletal fluorosis, bone sclerosis, tumor lesions, osteoporosis etc. In this work, a simple, convenient, sensitive, rapid and selective ‘Turn-On’ method has been developed to monitor sodium hexa-meta-phosphate by using a molecular rotor probe Thioflavin-T (ThT). The sensing principle is based on aggregation induced emission of ThT by HMP due to charge neutralisation of ThT via electrostatic interactions between mono-cationic dye ThT and hexa-anionic hexa-meta-phosphate to form a fluorescent ThT-HMP aggregate complex. The ThT-HMP aggregate system has been thoroughly investigated by using steady-state fluorescence, ground-state absorption, and time resolved fluorescence spectroscopy at different conditions, such as, salt, pH, temperature etc. Further, zeta potential measurements have also been performed to support the results. Also, the selectivity of ThT-HMP system has been tested against other common phosphate ions. The sensing method records a LOD of 116 nM for HMP over a wide linear concentration range of 0–6 μM. The sensing probe is highly selective for HMP over other common phosphate ions present in aqueous solution. Finally, the potential use of the probe has also been demonstrated in real water sample collected after rinsing the frozen green peas. Thus, the current sensing method is a sensitive fluorescence ‘Turn-On’ probe to detect HMP in real samples.