Curcumin nanoparticles combined with cloud point extraction for citrate determination in food and drug samples

•Green curcumin nanoparticles are used as a biomaterial in cloud point extraction.•The method uses citrate ion interaction with curcumin nanoparticles and Fe3 + in micellar media.•The developed cloud point extraction was used for monitoring citrate concentration.•The method was used for citrate detection in lemon juice and pharmaceutical samples.

In the current work, the enriched curcumin nanoparticles (CURNs) in nonionic surfactant phase in the presence of Fe3 + has been utilized for colorimetric recognition of citrate ions. The absorption intensity of CURN-Fe3 + complex transferred into the surfactant rich phase is decreased upon the addition of citrate ion owing to its interaction with citrate ions and consequently the formation of new complex (CURN-Fe3 +-citrate). This decrease in the absorption intensity of surfactant rich phase is proportional to the citrate concentration and was utilized for colorimetric sensing of citrate ions. The reaction conditions such as pH of the sample solution, concentration of Fe3 +, electrolyte and CURNs were appraised and optimized. Under the optimum experimental conditions, the proposed method demonstrated two linear calibration intervals in the concentration ranges of 3–100 ng mL− 1 and 100–600 ng mL− 1 of citrate with a detection limit of 1.7 ng mL− 1. The relative standard deviations (RSD) of 2.91% and 0.97% for 8 replicated measurements of 10 ng mL− 1 and 400 ng mL− 1 of citrate, respectively, indicate that developed method has good reproducibility. Eventually, the practical efficiency of the developed method was demonstrated to the analysis of citrate in lemon juice and pharmaceutical samples with satisfactory results.