title: Detection of anions by normal Raman spectroscopy and surface-enhanced Raman spectroscopy of cationic-coated substrates.
abstract: The use of normal Raman spectroscopy and surface-enhanced Raman spectroscopy (SERS) of cationic-coated silver and gold substrates to detect polyatomic anions in aqueous environments is examined. For normal Raman spectroscopy, using near-infrared excitation, linear concentration responses were observed. Detection limits varied from 84 ppm for perchlorate to 2600 ppm for phosphate. In general, detection limits in the ppb to ppm concentration range for the polyatomic anions were achieved using cationic-coated SERS substrates. Adsorption of the polyatomic anions on the cationic-coated SERS substrates was described by a Frumkin isotherm. The SERS technique could not be used to detect dichromate, as this anion reacted with the coatings to form thiol esters. A competitive complexation method was used to evaluate the interaction of chloride ion with the cationic coatings. Hydrogen bonding and pi-pi interactions play significant roles in the selectivity of the cationic coatings.
authors: SPAWAR Systems Center San Diego, Code 236, San Diego, California 92152, USA.
authors: P A
authors: PA
authors: Mosier-Boss
authors: S H
authors: SH
authors: Lieberman
mesh_terms: D000838:Anions / Q000032:analysis / Q000737:chemistry; D002840:Chromates / Q000032:analysis* / Q000737:chemistry; D003486:Cyanides / Q000032:analysis* / Q000737:chemistry; D004566:Electrodes; D004867:Equipment Design; D007220:Industrial Waste / Q000032:analysis; D009566:Nitrates / Q000032:analysis* / Q000737:chemistry; D010472:Perchlorates / Q000032:analysis* / Q000737:chemistry; D010710:Phosphates / Q000032:analysis* / Q000737:chemistry; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D017670:Sodium Compounds / Q000032:analysis* / Q000737:chemistry; D012989:Soil Pollutants / Q000032:analysis; D013059:Spectrum Analysis, Raman / Q000295:instrumentation / Q000379:methods*; D013431:Sulfates / Q000032:analysis* / Q000737:chemistry; D013438:Sulfhydryl Compounds; D013499:Surface Properties; D014874:Water Pollutants, Chemical / Q000032:analysis
chemical_list: D000838:Anions; D002840:Chromates; D003486:Cyanides; D007220:Industrial Waste; D009566:Nitrates; D010472:Perchlorates; D010710:Phosphates; D017670:Sodium Compounds; D012989:Soil Pollutants; D013431:Sulfates; D013438:Sulfhydryl Compounds; D014874:Water Pollutants, Chemical; C031068:sodium perchlorate