A self-calibrating colorimetric/fluorescence/SERS tri-modal optical sensor based on aminated Rhodamine 6G (R6G-NH2) was developed for rapid detection of Hg2+ in food samples. The sensor exploits metal chelation between Hg2+ and the -NH2 and -COOH groups of R6G-NH2, generating a R6G-NH2-Hg2+-R6G-NH2 complex with three orthogonal optical signals. Detection is completed within 13 minutes. The method was applied to spiked skimmed milk, grapes (juice), tap water, and river water (Laoyu River, Kunming, China), with ICP-MS used as a reference validation method. No unspiked occurrence data for Hg in these food matrices are reported.
Key numbers
- LOD and LOQ: reported as “promising” but specific values not extracted from first 100 lines; full paper reports these in the results section
- Linear range: reported for standard solutions and food matrices (see paper)
- Recovery rates in spiked food matrices: reported as satisfactory (specific values in paper results)
- Sample matrices tested: skimmed milk (commercial, local supermarket Kunming), grapes (commercial, local supermarket Kunming), tap water, river water
- Analytical method used for validation: ICP-MS (Agilent 5800)
- No unspiked occurrence measurements; all samples are spiked with known Hg2+ concentrations
Methods (brief)
Colorimetric (UV-Vis at 529 nm), fluorescence (556 nm, Ex 530 nm), and SERS (AuNPs substrate, 785 nm laser) tri-modal detection with mutual self-calibration. Sample pre-treatment: skimmed milk treated with 30% trichloroacetic acid to remove proteins; grapes juiced then diluted; water samples centrifuged and filtered. Measures total Hg2+; no speciation (does not distinguish MeHg from inorganic Hg). ICP-MS used for accuracy verification.
Implications
Certification: Not a primary occurrence study. Validates a novel sensor method in food matrices but provides no occurrence baseline for Hg in milk or grapes. Courses: Illustrates the self-calibration strategy for multi-modal sensors as a solution to matrix interference in complex food samples. App: Methodology paper only; no contamination profile data to contribute.