Determination of Food Oxalates Using Silica-Titania Xerogel Modified with Eriochrome Cyanine R.Development of a Dispersive Liquid-Liquid Microextraction Method Combined with UV-Visible Spectrophotometry for Determination of Trace Aluminum(III) in Water, Wastewater, Food, Biological, and Pharmaceutical Samples.Direct, sensitive determination of trace amounts of dissolved ferric iron in natural water by light absorption ratio variation spectrometry.Determination of vanadium by solid-phase spectrophotometry after its preconcentration as an Eriochrome Cyanine R complex on a dextran-type exchanger.