Abstract :
[en] Surface-enhanced Raman scattering (SERS), discovered in 1978, is a recent technique enabling to circumvent the main limitations of classical Raman spectroscopy by dramatically exalting the Raman scattering of the target molecules which are adsorbed or very closed to metallic surfaces while reducing the fluorescence impact on spectra [1]. This technique combines the sensitivity of the fluorescence keeping the structural information of molecules obtained from the SERS spectrum [2]. This last point allows to implement multiplex analyses. Moreover, it is possible to perform Surface-enhanced Raman chemical imaging (SER-CI) analyses which enable to acquire a visual representation of samples combining spectral and spatial measurements. Therefore SERS could become an attractive technique in numerous fields such as pharmaceutical and biomedical research.
In this context, the feasibility of developing quantitative approaches using SERS and SER-CI on a pharmaceutical model was studied. The aim was to develop methods allowing the quantification of 4-aminophenol (4-AP) in a pharmaceutical formulation based on paracetamol. 4-AP is the main impurity of paracetamol and is actively research because of its toxicity.
This pharmaceutical model was first investigated using SERS and a quantitative method enabling to quantify 4-AP from 3 to15 µg/mL was developed and validated using the standard addition method as a calibration method [3]. From these results, the possibility of developing a quantitative approach using SER-CI was investigated. Tablets based on paracetamol comprising different concentrations of 4-AP were prepared. Different ways to cover the sample surface by the SERS substrate were tested and a homogeneity study was performed to improve the repeatability of SER-CI analyses. Different spectral intensity normalizations were also tested in order to optimize the SER-CI method. Finally, a quantitative approach using SER-CI was developed allowing the quantification of 4-AP from 0.025% to 0.2% (w/w) in paracetamol tablets [4]. This first quantitative approach could pave the way to quantitative analysis of small molecules using SER-CI in complex matrices.
References
[1] P.L. Stiles, J.A. Dieringer, N.C. Shah, R.P. Van Duyne, Annu. Rev. Anal. Chem. 1 (2008) 601-626.
[2] R.F. Aroca, R.A. Alvarez-Puebla, N. Pieczonka, S. Sanchez-Cortez, J.V. Garcia-Ramos, Adv. Colloid Interface Sci. 116 (2005) 45-61.
[3] C. De Bleye, E. Dumont, E. Rozet, P.-Y. Sacré, P.-F. Chavez, L. Netchacovitch, G. Piel, Ph. Hubert, E. Ziemons, Talanta 116 (2013) 899-905.
[4] C. De Bleye, P.-Y. Sacré, E. Dumont, L. Netchacovitch, P.-F. Chavez, G. Piel, P. Lebrun, Ph. Hubert, E. Ziemons, J. Pharm. Biomed. Anal. (in Press)
