Rouhollah Khani - Assistant Professor, Department of Chemistry, College of Sciences, University of Birjand
Seyed Mahdi Nurbakhsh - MSc Student, Department of Chemistry, College of Sciences, University of Birjand

Ascorbic acid (AA), also known as vitamin C, is one of the basic vitamins significantly essential for humans and animals in biological systems and plays a considerable role in many life processes including amino acid metabolism, collagen formation and ion absorption. A rapid, selective and sensitive probe based on the Fe(III) modulated nitrogen-doped graphene quantum dots (N-GQDs) was developed and applied as fluorescence probe for AA detection. This procedure involves synthesis via the pyrolysis of citric acid, as a source of carbon, and tris-hydroxymethylaminomethane, as a surface passivation agent. To examine the most important parameters including volume of N-GQDs, pH of thesolution, ultrasonic time, ionic strength and their interactions on the fluorescence intensity, a four factor central composite design (CCD) combined with response surface modeling (RSM) was implemented. Under optimal conditions, the method showed a response to AA within a concentration range of ۳.۰– ۷۰ μmol L−۱ with a good linear relationship and the relative standard deviation for AA was ۴.۲%. The developed probe was successfully applied for the determination of AA in beverage samples with quantitative recoveries from ۹۵.۰ % to ۱۰۲.۳ %..

Ascorbic acid, Nitrogen-doped graphene quantum dots, Fluorescence probe, Experimental design