title: Semi-quantitative analysis of indigo carmine, using silver colloids, by surface enhanced resonance Raman spectroscopy (SERRS).
abstract: The application of surface enhanced resonance Raman spectroscopy (SERRS) to the semi-quantitative analysis of the dye, indigo carmine, has been examined using citrate-reduced silver colloids. Good linear correlations are observed for the dye band at 1580 cm(-1) in the concentration range 10(-7)-10(-5) and 10(-9)-10(-5) mol dm(-3), using laser exciting wavelengths of 514.5 [(R=0.9983)] and 632.8 nm [(R=0.9978)], respectively. At concentrations of dye above 10(-6) M the concentration dependence of the SERRS signals is non-linear due to the coverage of the surface of the colloidal particles by the dye being in excess of a full monolayer. At concentrations above 10(-6) M resonance Raman spectroscopy (RRS) can be employed for the quantitative analysis of the dye. An internal standard was used and a good linear correlation (R=0.997) was observed for the dependence of dye signal intensities at 1580 cm(-1) in the concentration range 10(-5)-10(-4) M using a laser exciting wavelength of 514.5 nm. The limits of detection of indigo carmine by SERRS (514.5 nm), SERRS (632.8 nm) and solution RRS (514.5 nm) are found to be 0.9, 1 and 38 ppm, respectively.
authors.affiliation: Vibrational Spectroscopy Centre, School of Chemical and Life Sciences, University of Greenwich, Chatham Maritime Campus, Kent ME4 4TB, UK.
authors.forename: I T
authors.initials: IT
authors.lastname: Shadi
authors.forename: B Z
authors.initials: BZ
authors.lastname: Chowdhry
authors.forename: M J
authors.initials: MJ
authors.lastname: Snowden
authors.forename: R
authors.initials: R
authors.lastname: Withnall
mesh_terms: D003102:Colloids; D007203:Indigo Carmine / Q000032:analysis / Q000737:chemistry*; D018030:Silver Compounds; D013059:Spectrum Analysis, Raman
chemical_list: D003102:Colloids; D018030:Silver Compounds; D007203:Indigo Carmine