A high-sensitivity photometric method based on doped Sol-Gel glass detectors: determination of sub-ppb divalent iron

A novel high-sensitivity photometric method to determine trace concentrations of water pollutants is presented. The Sol-Gel procedure, a simple and efficient way to produce porous glasses at room temperature, is applied to entrap organic reagents (e.g. 1,10-phenanthroline) in glass matrices without resorting to complicated covalent bonding procedures. When these doped Sol-Gel glass detectors are immersed in water they concentrate the analyte [e.g. iron(II)] from the solution into the glass matrix. The glass detectors may then be analyzed by a conventional spectrophotometer. Thus, exceedingly low concentrations can be determined, e.g., the demonstrated detection limit of ferrous ions in aqueous solution is below 100 ppt.