Content area
Full text
http://crossmark.crossref.org/dialog/?doi=10.1007/s00216-016-9454-7&domain=pdf
Web End = http://crossmark.crossref.org/dialog/?doi=10.1007/s00216-016-9454-7&domain=pdf
Web End = Anal Bioanal Chem (2016) 408:36993706 DOI 10.1007/s00216-016-9454-7
RESEARCH PAPER
An ascorbic acid sensor based on cadmium sulphide quantum dots
Manjunatha Ganiga1 & Jobin Cyriac1
Received: 17 November 2015 /Revised: 25 February 2016 /Accepted: 28 February 2016 /Published online: 29 March 2016 # Springer-Verlag Berlin Heidelberg 2016
Abstract We present a Frster resonance energy transfer (FRET)-based fluorescence detection of vitamin C [ascorbic acid (AA)] using cadmium sulphide quantum dots (CdS QDs) and diphenylcarbazide (DPC). Initially, DPC was converted to diphenylcarbadiazone (DPCD) in the presence of CdS QDs to form QDDPCD. This enabled excited-state energy transfer from the QDs to DPCD, which led to the fluorescence quenching of QDs. The QDDPCD solution was used as the sensor solution. In the presence of AA, DPCD was converted back to DPC, resulting in the fluorescence recovery of CdS QDs. This fluorescence recovery can be used to detect and quantify AA. Dynamic range and detection limit of this sensing system were found to be 60300 nM and 2 nM, respectively. We also performed fluorescence lifetime analyses to confirm existence of FRET. Finally, the sensor responded with equal accuracy to actual samples such as orange juice and vitamin C tablets.
Keywords Frster resonance energy transfer (FRET) .
Ascorbic acid . Vitamin C . Fluorescence sensor
Introduction
Vitamin C [ascorbic acid (AA)] is an essential nutrient because of its involvement in the synthesis of vital biomolecules such as collagen, carnitine, and many neurotransmitters. The recommended dietary allowance for AA is 7590 mg/d. AA deficiency leads to diseases such as anemia, gingivitis, and scurvy. It is also reported that under oxidative stress, the concentration of AA will be significantly decreased in the body [1]. Besides, extremely high AA levels in the body may cause renal disorders resulting from the formation of oxalic acid from AA, which is then converted into calcium oxalate. Therefore, the detection and quantification of AA in medicinal products, natural sources, and body fluids are essential for maintaining optimal levels [24].
Several analytical tools have been reported for detecting AA, including electrochemical [5], colorimetric [6, 7], spectrofluorimetric [8, 9], and chromatographic [10, 11] techniques. Of these, spectrofluorimetric platforms are advantageous because of their high sensitivity, simplicity, and selectivity. Many fluorimetric assays emphasize...