Rapid test methods for minor components analysis of hydraulic cement. Spectrophotometric determination of manganese oxide content of Portland cement and cement raw meal

A rapid, sensitive and highly selective spectrophotometric method for the d etermination of manganese oxide content of Portland cement and cement raw m eal is developed. The method is based on the reaction of manganese(II) with 1,2,4 trihydroxyanthraquinone (purpurin, PURP) in 50% v/v ethanol-water so lution at pH 8.5. The solution equilibria of manganese chelates are demonst rated and characterized for delineating optimal conditions of the complexat ion reaction and analytical aspect of the Mn-PURP system. The analysis of c ement materials of variable manganese content is feasible over the concentr ation range 1.67-8.13 mu g ml(-1) Mn, the limit of detection (at the 95% co nfidence level) of the method is 68 ng ml(-1) for manganese. Under optimum conditions, the use of first derivative spectrophotometry has the advantage of high sensitivity than normal spectrophotometric method and allows the d etermination of 0.5 mu g ml(-1) of manganese. (C) 1999 Elsevier Science B.V . All rights reserved.