Test determination of reducing agents using noncovalently immobilized quinonimine indicators

The noncovalent immobilization of indophenols (2,6-dichloroindophenol and 2,6-dibromoin-doguaiacol) and indamines (Variamine Blue and Bindshendler’s Green) on reversed-phase silica gels and ion exchangers was studied. It was shown that the properties of indicator powders can be improved by the double modification of reversed-phase silica gels with cetyltrimethylammonium chloride and 2,6-dichloroindophenol or with dodecyl sodium sulfate and Bindshlender’s Green. Ionization constants and formal redox potentials of the noncovalently immobilized quinonimine compounds were determined by solid-phase spectrophotometry. Indicator tubes and indicator powders were proposed for the test determination of 0.3–1000 mg/L ascorbic acid and 0.02–3.0 mg/L iron(II)