Analytical Sciences

Colorimetric Detection of Ascorbic Acid Based on the Trigger of Gold Nanoparticles Aggregation by Cr(III) Reduced from Cr(VI)

Ning SUI,* Fengya LIU,* Tailing LI,* Lina WANG,** Tao WANG,* Manhong LIU,* and William W. YU*,***

*College of Materials Science and Engineering, Qingdao University of Science and Technology, Qingdao 266042, China
**College of Environment and Safety Engineering, Key Laboratory of Eco-Chemical Engineering, Ministry of Education, Qingdao University of Science and Technology, Qingdao 266042, China
***Department of Chemistry and Physics, Louisiana State University, Shreveport, LA 71115, USA

Au nanoparticles (AuNPs) dispersed in water were stabilized by tripolyphosphate (P₃O₁₀⁵⁻). When Cr₂O₇²⁻ (Cr(VI)) was present, the AuNPs did not change; when Cr³⁺ (Cr(III)) was present, the AuNPs would aggregate because of cooperative metal-ligand reaction. Aggregated AuNPs showed different color from the non-aggregated ones. Thus, a simple colorimetric assay was made using AuNPs-Cr(VI) to detect ascorbic acid (AA). Upon introducing AA to the AuNPs-Cr(VI) system, Cr(VI) was reduced to Cr(III), and the aggregation of AuNPs occurred. This colorimetric assay performed high selectivity and a linear concentration response in the range of 0.2 to 10 μM; its limit of detection was 0.15 μM.

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