Journal
MICROCHIMICA ACTA
Volume 181, Issue 9-10, Pages 1069-1075Publisher
SPRINGER WIEN
DOI: 10.1007/s00604-014-1214-9
Keywords
Fluorescence; Cu nanoclusters; Polyethyleneimine; Sudan I . II . III . IV
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Funding
- National Natural Science Foundation of China [21273174, 20975083]
- Municipal Science Foundation of Chongqing City [CSTC-2013jjB00002]
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We report that the intensity of the blue fluorescence of copper nanoclusters coated with polyethyleneimine (PEI) is strongly reduced in the presence of the food dyestuffs Sudan I-IV. This finding was exploited in a label-free fluorescence assay for these Sudan dyes both in ethanol and aqueous solutions. The PEI-capped nanoclusters have an average diameter of 1.8 nm and are displaying, under 355 nm excitation, a blue emission at 480 nm that matches the absorption bands of the Sudan dyes. The clusters are stable in solution for at least 1 month. Under optimum conditions, this assay can be applied to the quantification of the dyes Sudan I, II, III, and IV, respectively, in the 0.1-30, 0.1-30, 0.1-25, and 0.1-25 mu M concentration ranges, and the detection limits (3 sigma/slope) are 65, 70, 45, and 50 nM, respectively. The capability of reducing the fluorescence of the PEI-capped copper nanoclusters is directly related to the number of the functional groups in that Sudan III and IV give lower detection limits. This analytical scheme exhibits a remarkably high selectivity for the Sudan dyes over potentially interfering substances. The method was successfully applied to determine Sudan I, II, III, and IV in hot chilli powder.
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