Determination of manganese

The method is based upon the titration of manganese) II) ions with permanganate in neutral pyrophosphate solution  

Large amounts of chloride, cobalt(II), and chromium(III) do not interfere iron(III), nickel, molybdenum)VI), tungsten(VI), and uranium(VI) are innocuous nitrate, sulphate, and perchlorate ions are harmless. Large quantities of magnesium, cadmium, and aluminium yield precipitates which may co-precipitate manganese and should therefore be absent. Vanadium causes difficulties only 

For initial practice in the method determine the manganese content of anhydrous manganese(II) sulphate. Heat manganese(II) sulphate crystals to 280 °C, allow to cool, grind to a fine powder, re-heat at 280 °C for 30 minutes, and allow to cool in a desiccator. Weigh accurately about 2.2 g of the anhydrous manganese(II) sulphate, dissolve it in water and make up to 250 mL in a graduated flask. 

Prepare a 0.02 M solution of potassium permanganate and standardise it against arsenic(III) oxide. 

Prepare 5M sodium hydroxide solution using analytical grade material test a 10 mL sample for reducing agents by adding a drop of the permanganate solution no green coloration should develop. 

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G7 DETERMINATION OF MANGANESE IN PRESENCE OF IRON ANALYSIS OF FERROMANGANESE... 

The method can be readily adapted to the determination of manganese in steel and in manganese ores. 

The above considerations will be illustrated by the simultaneous determination of manganese and chromium in steel and other ferro-alloys. The absorption spectra of 0.001 M permanganate and dichromate ions in 1M sulphuric acid, determined with a spectrophotometer and against 1M sulphuric acid in the reference cell, are shown in Fig. 17.20. For permanganate, the absorption maximum is at 545 nm, and a small correction must be applied for dichromate absorption. Similarly the peak dichromate absorption is at 440 nm, at which permanganate only absorbs weakly. Absorbances for these two ions, individually and in mixtures, obey Beer s Law provided the concentration of sulphuric acid is at least 0.5M. Iron(III), nickel, cobalt, and vanadium absorb at 425 nm and 545 nm, and should be absent or corrections must be made. 

Kucera J, and Soukal L (1998) Low uncertainty determination of manganese and vanadium in environmental and biological reference materials by instrumental neutron activation analysis. Fresenius J Anal Chem 360 415-418. 

In a method for titrimetric determination of manganese in pyrolusite ore, addition of the powdered ore to a cold 20% solution of the salt causes vigorous decomposition to occur. 

Olafsson [427] has described a semiautomated determination of manganese in seawater using leucomalachite green. The autoanalyser had a 620 nm interference filter and 50 minute flow cells. Findings indicated initial poor precision was related to pFl, temperature, and time variations. With strict controls on sample acidity and reaction conditions, the semiautomated method had high precision, at least as good as that achieved by preconcentration and atomic absorption procedures, and provided precise, rapid, shipboard information... 

Brewer and Spencer [428] have described a method for the determination of manganese in anoxic seawaters based on the formulation of a chromophor with formaldoxine to produce a complex with an adsorption maximum at 450 nm. Sulfide (50 xg/l), iron, phosphate (8 ig/l), and silicate (100pg/l) do not interfere in this procedure. The detection limit is 10 pg/1 manganese. 

Biddle and Wehry [429] carried out fluorometric determination of manganese II in seawater via catalysed enzymic oxidation of 2,3-diketogluconate. The detection limit was 8 pmoll-1 Mn (II). 

Oxime 2 has been extensively used only as an analytical reagent (determination of manganese by photometry), jet-fuel additive and more recently in polymer synthesis d . 

M. C. Yebra and A. Moreno-Cid, On-line determination of manganese in solid seafood samples by flame atomic absorption spectrometry, Anal. Chim. Acta, 477(1), 2003, 149-155. 

M. Grotti, R. Leardi, C. Gnecco and R. Frache, Determination of manganese by graphite furnace atomic absorption spectrometry matrix eflects control by multiple linear regression model, Spectrochim. Acta, Part B., 54(5), 1999, 845-851. 

Weiss, H.V. and Bertine, K.K. (1973) Simultaneous determination of manganese, copper, arsenic, cadmium, antimony and mercury in glacial ice by radioactivation. Analytica Chimica Acta, 65(2), 253-59. 

Gates, E. M., and G. H. Ellis A Microcolorimetric Method for the Determination of Manganese in Biological Materials with 4,4 -Tetramethyldiaminotri-phenylmethane. J. Biol. Chem. 168, 537 (1947). 

Abdullah, M. I. The Automatic Determination of Manganese in Silicate Rocks and Sediments. Anal. Chim. Acta 40, 526 (1968). 

Dong et al. [ 13] evaluated sampling and analytical errors for the determination of manganese in soils, and no doubt the conclusions reached in this work could be applied to other elements. 

The determination of manganese in soils is also discussed under Multi-Metal Analysis of Soils in Sects. 2.55 (inductively coupled plasma atomic... 

Gine et al. [29] has described a semi-automatic determination of manganese in plant digests using flow injection analysis. This technique utilises the introduction of the sample into a continuously flowing carrier stream of formaldoxime reagent. When injected, the sample is pushed by this stream and dispersed into the reagent stream, whereupon the required reaction takes place. The coloured complex is then carried into a spectrophotometric flow cell, where the absorbance is measured after an exactly defined time interval. 

Figure 7.1. Flow diagram of the system for determination of manganese. P peristaltic pump S injection port R reaction coil (length 30 cm) M mixing coil (length 60 cm) and W waste. The numbers in the pump are the flow rates in ml/min of the carrier, reduction, reagent, neutralisation and masking streams, which correspond to (a), (b), (c), (d) and (e), respectively. The distances S-C and C-B are approximately 2 cm. From [29]...

In order to prevent the reduction between iron(II) and formaldoxime occurring, another iron complexing agent (potassium cyanide) was used in the presence of a reductant (ascorbic acid) that reduces iron(III) to iron(II). Aluminium, titanium, uranium, molybdenum and chromium also form light-coloured complexes that normally do not interfere in the determination of manganese in water or plant material by this method. If the aluminium or titanium concentrations are higher than 40 ppm an additional masking flow of tartrate is recommended [31]. 

International Standard Organization. 1986. Water quality. Determination of manganese. Formaldoxime spectrometric method. ISO 6333. International Organization for Standardization, Case Postale 56, CH-1211, Geneva 20 Switzerland. 

Often the chemical speciation of iron, and hence its availability, is significant in iron supplements. Thus atomic absorption may be preceded by separation procedures [96]. To measure total iron in multi-vitamin preparations the sample can be taken up in hydrochloric acid and the determination made in an air/acetylene flame. Care must be taken with high mineral content samples to avoid inter-element interferences and the method of standard additions may be employed. Similar comments may be made about the determination of manganese and copper [97, 98], except that interferences are here less likely, but there may be a requirement for lower levels to be determined. 

It is worth while noting that hydrogen ions are formed during the reaction, and if these build up to a higher concentration they may reverse the process. In order to make the reaction complete, the solution must be buffered. The reaction is utilized for the titrimetric determination of manganese by the so-called Volhard-Wolff method, when zinc oxide is used as a buffer. 

Tinggi, U., Reilly, C., Patterson, C. Determination of manganese and chromium in foods by atomic absorption spectrometry after wet digestion. Food Chem. 60, 123-128 (1997)... 

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