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  • Author: Andriana Surleva x
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Ninhydrin-based spectrophotometric assays of trace cyanide

Abstract

The extreme toxicity of cyanide, its wide industrial application as well as its continued illegal use generate research interest in different fields of science, imposing multidisciplinary approach to study cyanide poisoning. We show here that the reaction between cyanide and ninhydrin can be performed at ambient conditions; however, the ninhydrin reagent has to be freshly prepared in oxygen free solvent. Besides, we show that the reading of the absorbance at 485 nm might be more suitable and reliable than that at 590 nm, where the pH-dependent blue colored cyanide-ninhydrin adduct is less stable. Ninhydrin-based color reagent can be used to quantify the cyanide released from plant seeds. In sodium carbonate medium, the proposed assay is fast, cheap and environmentally friendly

Open access
Contribution to Casein Determination by UV Spectrophotometry

Abstract

In the present paper, the interaction between copper ions and proteins is presented, in order to elaborate a simple and rapid spectrophotometric assay of casein in milk. Under alkaline conditions, copper ions form the biuret complex with the proteins, which can be used in protein determination. Although very specific, the biuret method is less sensitive. Using insoluble copper phosphate, casein is able to extract copper ions, with which it forms the biuret complex, while either the complex or copper ions could be determined in the ultraviolet range. Indeed, an increased absorbance of biuret complex at 215 nm was found. Nevertheless, copper ions can be determined in UV as well, their concentration being proportional to that of casein. When used tetraglycine instead casein, mass spectrometric measurements at pH higher than 11 revealed the formation of complexes with many copper ions bound to each peptide bond-containing molecule. Nevertheless, on diluting the biuret solution the complex may dissociate leading to very complex UV spectra that should be further studied.

Open access