Direct Spectrophotometric Determination of Aluminum Oxide in Portland Cement and Cement Clinker

Abstract

Abstract A spectrophotometric study of the complexation reaction between Al3+ and Quinizarin (QUIN) is carried out to ascertain the suitability of the complex formed for direct spectrophotometric determination of aluminum. The absorbance at 550 nm, due to the aluminum-QUIN complex, formed at pH 3.8, is recommended for the determination of aluminum content of portland cement and cement clinker. The proposed method is simple and rapid and possesses reasonable selectivity. Interference of iron (III), generally present in portland cement, is eliminated by addition of ascorbic acid. The results obtained for several SRMs, portland cement samples, and a variety of cement materials demonstrate that the proposed method allows precise and accurate determination of Al2O3 content over the concentration range 1.4 to 5.75 μg/mL of aluminum. The determination of Al can be carried out successfully in absence of a masking agent by using first-derivative spectrophotometry. Verification and use of control charts in spectrophotometric determination of Al is achieved. Record of verifier response during routine operation establishes that the method is being maintained in statistical control.