Optimization of Test Placer Composition for Express Colorimetric Determination of Mobile Forms of Phosphorus in Soil and Water Samples

Abstract

Abstract The paper presents the optimized methods of manufacturing test placers for quantitative and visual-blister colorimetric determination of phosphate ion concentration in a blister cell and a test tube. The test placer contains all the reagents for the analytical reaction. Placers allow the quantitative determination of phosphates in various objects without preliminary preparation of reagent solutions. In a blister cell with a diameter of 6 mm, a much more intense blue color was achieved with a solution layer of no more than 2 mm. The application of reagents to the surface of the silica gel allows them to avoid contact until the chemical analytical reaction takes place. The composition of placers and the conditions for applying reagents are improved. Hydrosulfate ions are able to provide a sufficiently high acidity when adding a few drops of the solution. The reaction proceeds in the volume of the added test solution, which is 2–3 drops.