Selective spectroscopic methods for water analysis

Abstract

<p>This dissertation explores in large part the development of a few types of spectroscopic methods in analysis of water. Methods for the determination of some of the most important properties of water like pH, metal ion content, and chemical oxygen demand are investigated in detail. The first of the five papers included in this dissertation describes the synthesis, acid-base reactivity and metal ion binding selectivity of two novel crown ether compounds, N,N'-bis(2-hydroxy-5-nitrobenzyl)-4,13-diazadibenzo-18-crown- 6 (CCE) and N,N'-bis(7-hydroxy-4-methylcoumarin-8-methylene)-4,13-diazadibenzo-18-crown-6 (FCE). Extraction constants for Ba(II), Ca(II), Cd(II), Cu(II), Hg(II), Pb(II), and Sr(II) have been determined for both reagents. Both CCE and FCE exhibit an unprecedented selectivity of >106 in the binding of Hg(II) over the other divalent metal cations;The characterization of optical properties, acid-base equilibria, and metal binding capabilities of CCE in a mixed micellar solution are reported in the second paper. The formation constants for Hg(II), Cd(II), Ca(II) and Sr(II) have been determined. The potential application to a spectrophotometric chemical analysis based on the selectivity of CCE for Cd(II) is examined;The third paper describes an efficient method for minimization of chloride interference for COD determinations in aqueous samples without using a mercury salt to mask chloride ion. Chloride is removed as HCl gas from an acidified sample solution at 150°C in a closed vial by adsorption onto a bismuth-based adsorbent held in a specially designed Teflon-basket. The effects of adsorbent composition, basket design, acid concentration, temperature, reflux time, and silver(I) in the removal of chloride ion and the COD determination are also discussed;The formation of an ordered monolayer of 4-aminothiophenol (ATP) on gold, electrostatic attachment of anthraquinone mono- and disulfonates to the protonated ATP monolayer, and the determination of the orientation of each of the adsorbed anthraquinone sulfonates from their respective infrared spectra are described in the fourth paper. The orientation of the adsorbed anthraquinone mono- or disulfonate is largely directed by the anionic sulfonate group that binds to the surface bound ammonium group. Finally, the development of a thin-film optical sensor for measuring pH is described in the appendix.</p>