Quantitative Detection of Alcian Blue 8GX in the Low Concentration Range Using Surface-Enhanced Resonance Raman Spectroscopy

Abstract

The viability of the application of surface-enhanced resonance Raman spectroscopy (SERRS) to the quantitative analysis of the dye alcian blue 8GX has been examined with the use of citrate- and borohydride-reduced silver colloids. A good linear correlation is observed for the dependence of the SERRS signal intensities at 1344 and 1536 cm⁻¹ (R = 0.992 and 0.994, respectively) on dye concentrations in the range of 10⁻⁹–10⁻⁷ M, when using the citrate-reduced silver sol. Likewise, a good linear correlation is also observed for the dependence of the SERRS signal intensities at 1344 and 1536 cm⁻¹ (R = 0.978 and 0.959, respectively) on dye concentrations in the range 10⁻¹⁰–10⁻⁹ M, when using the borohydride-reduced silver sol. At concentrations of dye above 10⁻⁷ M, the concentration dependence of the SERRS signals is nonlinear, almost certainly due to the coverage of the surface of the colloidal silver particles by the dye being in excess of a full monolayer. However, at concentrations of alcian blue greater than 10⁻⁷ M, resonance Raman spectroscopy (RRS) can be employed for quantitative analysis of the dye. When performing RRS, using methanol as an internal standard, we observed a good linear correlation for the dependence of the signal intensities at 1344 and 1536 cm⁻¹ (R = 0.995 for both bands) on the dye concentration in the 10⁻⁶–10⁻³ M range. The limits of detection of alcian blue by SERRS using a citrate-reduced silver sol, SERRS using a borohydride-reduced silver sol, RRS, and visible absorption spectroscopy are found to be 26 ppb, 203 ppt, 2 ppm, and 0.7 ppm, respectively.