Quantitative detection of alcian blue 8GX in the low concentration range using surface-enhanced resonance Raman spectroscopy

The viability of the application of surface-enhanced resonance Raman spectr oscopy (SERRS) to the quantitative analysis of the dye alcian blue 8GX has been examined with the use of citrate- and borohydride-reduced silver collo ids. ii good linear correlation is observed for the dependence of the SERRS signal intensities at 1334 and 1536 cm(-1) (R = 0.992 and 0.994, respectiv ely) 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 obs erved for the dependence of the SERRS signal intensities at 1334 and 1536 c m(-1) (R = 0.978 and 0.959, respectively) on dye concentrations in the rang e 10(-10)-10(-9) M, when using the borohydride-reduced silver sol. At conce ntrations of dye above 10(-7) M, the concentration dependence of the SERRS signals is nonlinear, almost certainly due to the coverage of the surface o f the colloidal silver particles by the dye being in excess of a full monol ayer. However, at concentrations of alcian blue greater than 10(-7) M, reso nance Raman spectroscopy (RRS) can be employed for quantitative analysis of the dye. When performing RRS, using methanol as an internal standard, we o bserved a good linear correlation for the dependence of the signal intensit ies at 1344 and 1536 cm(-1) (R = 0.995 for both bands) on the dye concentra tion in the 10(-6)-10(-3) hi range. The limits of detection of alcian blue by SERRS using a citrate-reduced silver sol, SERRS using a borohydride-redu ced silver sol, RRS, and visible absorption spectroscopy are found to be 26 ppb, 203 ppt, 2 ppm, and 0.7 ppm, respectively.