Selective Determination of Rutin by Fluorescence Attenuation of the CdS-2-mercaptopropionic Acid Nanocrystal Probe

Abstract

In this work, an analytical method for the determination of rutin was developed based on the CdS-2-mercatopropioinic acid (Cd-2MPA) luminescence attenuation. The optimized experimental parameters were: (1) the Tris-HCl buffer concentration (0.05 mol L⁻¹); (2) the pH of the system (7.4); (3) the amount of organic solvents (30% of methanol and acetonitrile) and the time required to stabilize the signal (30 min). The luminescence (387/498 nm) signal presented a linear range up to 4 × 10⁻⁵ mol L⁻¹ of rutin (Y = 3 × 104X + 0.99; r = 0.997). The limit of detection (based on x_b − 3 s_b of the signal attenuation curve) was 1.2 × 10⁻⁶ mol L⁻¹. It was observed that the attenuation of signal was caused by two effects: the contribution from the inner filter effect and a static luminescence quenching component. Luminescence lifetimes of CdS-2MPA in the presence and in the absence of rutin were the same, indicating the static nature of the quenching caused by rutin. No interferences were observed from the flavonoids hesperidin and hesperetin when these were present in concentrations as high as 10 times the one of rutin. In samples containing the flavonoid quercetin, thin layer chromatography (TLC) was used in order to previously separate the analyte since an inner filter effect from quercetin was expected. The TLC/CdS-2MPA attenuation approach enabled recoveries for rutin of approximately 99%. In pharmaceutical formulations and in simulated saliva samples recoveries were between 100 and 104%.

Keywords:

• CdS-2-mercaptopropioinic acid
• Fluorescence attenuation
• Rutin
• Semiconductor nanocrystals
• Thin-layer chromatography

Acknowledgments

The following scholarships are acknowledged: CNPq (Aucélio), FAPERJ (Aucélio), CAPES-PNPD project (da Silva), and CAPES (Carvalho). The authors thank scientific funding from FINEP, CNPq, and FAPERJ. The authors thank Dr. Sônia R. Louro (Physics Departments – PUC-Rio) for the lifetime measurements.

Notes

*Uncorrected curve. **Corrected curve.