Manganese concentration determinations

Mercury was determined after suitable digestion by the cold vapour atomic absorption method [40]. Lead was determined after digestion by a stable isotope dilution technique [41-43]. Copper, lead, cadmium, nickel, and cobalt were determined by differential pulse polarography following concentration by Chelex 100 ion-exchange resin [44,45], and also by the Freon TF extraction technique [46]. Manganese was determined by flameless atomic absorption spectrometry (FAA). 

Klinkhammer [432] has described a method for determining manganese in a seawater matrix at concentrations ranging from about 30 to 5500 ng/1. The samples are extracted with 4 nmol/1 8-hydroxyquinoline in chloroform, and the manganese in the organic phase is then back-extracted into 3 M nitric acid. The manganese concentrations are determined by graphite furnace atomic absorption spectrophotometry. The blank of the method is about 3.0 ng/1, and the precision from duplicate analyses is 9% (1 SD). 

Conditioning of the manganese oxide suspension with each cation was conducted in a thermostatted cell (25° 0.05°C.) described previously (13). Analyses of residual lithium, potassium, sodium, calcium, and barium were obtained by standard flame photometry techniques on a Beckman DU-2 spectrophotometer with flame attachment. Analyses of copper, nickel, and cobalt were conducted on a Sargent Model XR recording polarograph. Samples for analysis were removed upon equilibration of the system, the solid centrifuged off and analytical concentrations determined from calibration curves. In contrast to Morgan and Stumm (10) who report fairly rapid equilibration, final attainment of equilibrium at constant pH, for example, upon addition of metal ions was often very slow, in some cases of the order of several hours. 

For instance, the manganese determination by molecular absorption spectro(photo)metry can be made using different types of instruments which have various technical performances. Some results are shown (Fig. 4) for manganese concentration measurements with a DR 2000-wide bandwidth 8 nm (series 1) a Hewlett Packard 8452 A, bandwidth 2 nm (series 2) and a Spe-cord M 40-narrow bandwidth 1 nm (series 3). 

When the manganese concentration exceeds 25 a/o, the amorphous phase is gradually replaced by a crystalline bcc phase [129, 146-150], Although the x-ray diffraction pattern suggests the structure to be W-type (Figure 28(a)), it was determined by electron diffraction that the x-ray pattern only showed the third order reflections of a y-brass related D8i 3 structure [148]. It was concluded that the electro-deposited phase was a cubic variant of Mru Ah with a lattice parameter of 0.9012 nm. It was further suggested to be the high temperature y 1 phase, which has a com-... 

The elemental concentrations determined in the metallic phase are given in Table III. The crudeness of the ceramic correction method just described adds additional uncertainty to some of these values (especially aluminum, manganese, and vanadium). Most values, however, are quite meaningful. 

Highly Catalyzed Experiments. In conjunction with experiments in which the manganese concentration was 2000 ppm, the model was first used to determine the mass transfer coefficient of calcium sulfite (T=40°C, pH=5.0). A reaction order of 1.5 was obtained from previous liquid phase kinetic studies with a rate constant of 85 1 ° 5 mol 0,5 sec-1 (25). Computer curves were generated using a series of mass transfer coefficients and plotted along with the experimental kinetic results on Figure 7. A mass transfer coefficient of 0.015 cm/sec most closely fits the data. The bulk pH drops quickly during the initial several seconds and then stays around 2.9, but the surface pH remains almost constant at 5.15 which implies that the oxidation only has small influence on the surface conditions. 

Methods were used to determine levels of chromium, lead, and cadmium in hair. Manganese concentrations in hair were evaluated for some, but not all, of the samples and tested one, but not both, new methods. However, it is assumed that both techniques will work for the trace element manganese. 

Kihira T, Mukoyama M, Ando K, et al. 1990. Determination of manganese concentrations in the spinal cords from amyotrophic lateral sclerosis patients by inductively coupled plasma emission spectroscopy. J Neurol Sci 98 251-258. 

Scope. The method is designed to determine manganese concentrations down to the 10 ng/g level in petroleum and petroleum products. 

E, coU MnSOD. Manganese superoxide dismutases are either dimeric or tetrameric enzymes containing monomeric units of approximately 22,000 mol (5). In general, eucaryotic MnSODs are dimers while prokaryotic MnSODs are tetramers. The structure has been established for a variety of manganese superoxide dismutases (6-8) however, the structure of the MnSOD from E. coli has not been determined. Therefore, the rate constants reported here are given per manganese concentration and not per enzyme concentration, where the manganese concentration of the enzyme was determined by atomic absorption, as discussed above. 

The quantity of dissolved Mn(II) in natural waters depends on the solubility of hydroxide, carbonate and sulphide. In most natural waters the equilibrium concentration of dissolved manganese is determined by the MnC03 solubility. The production of Mn(OH)2 is considered only in a stronger alkaline medium. In the presence of hydrogen sulphide and its ionic forms the Mn(II) solubility in alkaline media is limited by the MnS solubility and the equilibrium concentrations are the lowest under these conditions. 

From time to time throughout the experiments the pH was recorded, and a sample of precipitate and supernate was withdrawn from the stirred mixture by means of a syringe, and filtered through a 0.10-/xm pore-diameter membrane filter. The filtrate was analyzed for manganese by atomic absorption. The filter membrane with the precipitate was transferred to a small beaker and the oxide was dissolved in a measured excess of standardized oxalic acid and 0.2 mL of concentrated H2SO4. This solution was diluted to 100 mL the manganese was determined on... 

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