Xerogels doped with 1-(2-pyridylazo)-2-naphthol and Xylenol Orange: Indicator tubes and indicator powders for determining copper(II) and iron(III) in solution

Silica-based xerogels doped with l-(2-pyrilylazo)-2-naphthol and Xylenol Orange were prepared. The xerogels differ in the specific surface and the reagent concentration. Modified xerogels were used as indicator powders for determining copper(II) and iron(III) using indicator tubes. The effects of the reagent concentration in the indicator powder and its specific surface on the length of the colored zone were studied. Indicator tubes were developed for determining 0.3–300.0 mg/L copper(II) and 1.0–120.0 mg/L iron(III) in solutions. The results of determining copper(II) in plant mineral food and iron(III) in natural waters and ashed milk powder are presented.