High‐sensitivity Determination of Curcumin in Human Urine Using Gemini Zwitterionic Surfactant as a Probe by Resonance Light Scattering Technique

ABSTRACT Introduction Curcumin is a popular plant medicine that is extracted from turmeric dry rhizomes of Curcuma longa Linn. The study of curcumin is well established and is currently becoming a centre of attention. Objective To develop a steady and simple assay for curcumin determination at the nanogram level based on the intense resonance light scattering (RLS) enhancement due to the interaction between curcumin and phosphodiesters quaternary ammonium salt (PQAS). Methodology PQAS, a new kind of Gemini zwitterionic surfactant, was used as the probe for the determination of curcumin by the RLS technique. A series of validation experiments was also performed. Results A linear relationship was constructed between the Δ I RLS and the concentration of curcumin. The linear regression equation was presented as Δ I RLS = 8.37 + 44.92 c (µg/mL) with the regression coefficient r = 0.9987 ( n = 12) and the linear range was 0.08–60.0 µg/mL. The detection limit (3σ) was 2.6 ng/mL. Conclusion The proposed method can be used to detect the content of curcumin in human urine samples and this new assay using PQAS as a probe was more sensitive and displayed a wider linear range than that reported previously. Copyright © 2011 John Wiley & Sons, Ltd.