Monosegmented flow system exploiting multicommutation applied to spectrophotometric determination of manganese in soybean digests

• Published in: Analytica chimica acta Vol. 386; no. 1; pp. 129 - 135
• Main Authors: Smiderle, Marisa, Reis, Boaventura F, Rocha, Fábio R.P
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 09.04.1999; Elsevier
• Subjects: Agronomy. Soil science and plant productions; Analytical chemistry; Binary sampling; Biological and medical sciences; Chemistry; Exact sciences and technology; Flow analysis; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; Generalities. Analysis and diagnosis methods; Manganese determination; Monosegmented flow analysis; Multicommutation; Soil-plant relationships. Soil fertility. Fertilization. Amendments; Soybean; Spectrometric and optical methods; Multicommutation; Monosegmented flow analysis; Manganese determination; Soybean; Binary sampling; Flow analysis; Transition metal Ions; Chemical analysis; Sample preparation; Acid digestion; Solubilization; Manganese ion; Quantitative analysis; Flow injection; Ultraviolet visible spectrometry
• ISSN: 0003-2670; 1873-4324
• DOI: 10.1016/S0003-2670(99)00015-X

A flow system combining binary sampling and monosegmented flow implemented by multicommutation was developed to improve sensitivity and sampling rate of spectrophotometric methods based on slow chemical reactions. The flow network was assembled from a set of computer controlled three-way solenoid valves. The spectrophotometric method was based on manganese (II) oxidation by periodate in phosphoric acid medium to form the permanganate anion. The reaction is relatively slow and at 47°C a sample residence time of ca. 5 min is necessary to attain equilibrium conditions. However, by exploiting binary sampling and monosegmented flow analysis, quantitative conversion with a sampling rate of 50 determinations per hour was achieved. The procedure was applied to Mn determination in soybean digests, showing as profitable features a linear response for sample concentrations ranging from 2.50 to 40.00 mg l −1 Mn 2+, a relative standard deviation of 0.27% ( n=9) for a sample solution containing 17.1 mg l −1 Mn 2+, a low reagent consumption (30 mg NaIO 4 per determination) and a detection limit of 1.2 mg l −1 (99.7% confidence level). Results agreed with those obtained by inductively coupled argon plasma atomic emission spectrometry at 95% confidence level.