Online Flow-Based Spectrophotometric Determination of Ferrous Iron Mass Fraction and Total Iron Mass Fraction in Twenty-Seven Rock Reference Materials Using a Schlenk line Technique

We developed an online continuous-flow spectrophotometric method for determination of ferrous iron and total iron mass fractions in various types of geological certified reference materials (CRMs) using a Schlenk line technique to exclude oxygen during the digestion process. The continuous-flow technique enabled automatic, reliable and real-time analysis, and decreased sample and reagent consumption. The Schlenk line expels air to prevent oxidation during sample digestion. Compared with traditional spectrophotometric procedures, this analytical procedure is easier, more automated and more accurate. The composition of the acid matrix and time used to dissolve the samples were carefully examined. The procedure was tested on 186 replicates of twenty-seven rock CRMs, and the results showed good agreement with the compiled values from the literature. Based on the statistical data, the proposed procedure was found to be accurate within 0.12%m/mfor ferrous iron mass fraction and 0.084%m/mfor total iron mass fraction compared with the certified/recommended values. The proposed procedure is accurate, reproducible and has a high throughput (ten samples per hour).