β-cyclodextrin based platform for bimodal detection of o-toluidine and cholesterol: Electrochemical and fluorescence sensing

A novel dual-mode sensor based on the in-situ coupling of electrochemical (EC) and fluorescence (FL) assay for o-toluidine and cholesterol detection is reported. The detection platform was constructed by assembling nitrogen doped graphene quantum dots (N-GQDs), benzoquinone (BQ) and & beta;-cyclodextrin (& beta;-CD). Once the analyte is captured by & beta;-CD, a concentration-depended variation of the electrochemical and fluorescence signals occurs. Based on this meticulous design, low electrochemical (LODo-Toluidine = (5.53 & PLUSMN; 0.16) & mu;M; LODcholesterol = (2.10 & PLUSMN; 0.042) & mu;M) and fluorescence (LODo-Toluidine = (5.06 & PLUSMN; 0.15) & mu;M; LODcholesterol = (2.95 & PLUSMN; 0.23) & mu;M) detection limits were achieved. In addition, the platform showed good selectivity in the presence of various interfering agents as well as long storage stability. Finally, the proposed method was applied to detect cholesterol in pro-cessed cow milk as a real sample, with apparent recoveries between 93.18% and 102,91%.