Spectrophotometric methods for the determination of manganese

A comprehensive and critical review of the available spectrophotometric methods for the determination of manganese is presented. Details are given of a wide range of direct colour-forming reactions of manganese with organic ligands, which have been claimed to be of use in analysis for the metal. The use of the very sensitive kinetic methods of analysis is also discussed. It is found that there is a paucity of reliable detail concerning the general applicability of most methods to manganese determination and that there is even less detail on the comparative value of different methods for determination of the metal in particular types of matrix.     

The speciation of manganese in freshwaters

The extent of current knowledge regarding the speciation of manganese in freshwaters is delineated, and the analytical methods whereby such knowledge is obtained are discussed. Particular attention is paid in the review to the use of electron paramagnetic resonance spectroscopy.     

Facile colorimetric methods for the quantitative determination of tetramisole hydrochloride

A facile, rapid and sensitive methods for the determination of tetramisole hydrochloride in pure and in dosage forms are described. The procedures are based on the formation of coloured products with the chromogenic reagents alizarin blue BB (I), alizarin red S (II), alizarin violet 3R (III) and alizarin yellow G (IV). The coloured products showed absorption maxima at 605, 468, 631 and 388 nm for I-IV, respectively. The colours obtained were stable for 24 h. The colour system obeyed Beer's law in the concentration range 1.0-36, 0.8-32, 1.2-42 and 0.8-30 microg ml(-1) respectively. The results obtained showed good recoveries with relative standard deviations of 1.27, 0.96, 1.13 and 1.35%, respectively. The detection and determination limits were found to be 1.0 and 3.8, 1.2 and 4.2, 1.0 and 3.9 and finally 1.4 and 4.8 ng ml(-1) for I-IV complexes, respectively. Applications of the method to representative pharmaceutical formulations are represented and the validity assessed by applying the standard addition technique, which is comparable with that obtained using the official method.     

Comparison of three analytical methods for the determination of trace elements in whole blood

Three different analytical techniques were compared in a study of the role of trace elements in multiple sclerosis. Data for eight elements (Cd, Co, Cr, Cu, Mg, Mn, Pb, Zn) from neutron activation, flame atomic absorption and electrothermal atomic absorption methods were compared and evaluated statistically. No difference (probability less than 0.001) was observed in the elemental values obtained. Comparison of data between suitably different analytical methods gives increased confidence in the results obtained and is of particular value when standard reference materials are not available.     

Comparison of three spectrophotometric methods for the determination of gamma-oryzanol in rice bran oil

A comparison of the results obtained by applying three spectrophotometric methods (at fixed wavelength, second-derivative and multicomponent analysis) to the determination of gamma-oryzanol in rice bran oil is reported.At fixed wavelength the results are more accurate when using isopropyl alcohol, rather than n-heptane, to dilute the oil samples, because the absorption bands of gamma-oryzanol are red-shifted and the absorbance, measured at lambda(max)=327 nm, is less affected by the interference of the oil "matrix" (lambda(max)=314 nm in n-heptane).However, to obtain accurate results also in oils with a low content of gamma-oryzanol, it is necessary to perform the analysis using second-derivative ((2)D330.365) or multicomponent (lambda=310-360 nm) methods. The first one fully removes the interference of oil matrix whilst the second, which needs a specific computational program to process the spectrophotometric data, furnishes evidence the presence of some unexpected interference in the analysis and/or standards which are not representative of the analysed samples, from the square root of the sum of the squared differences at each point between the linear combination of the standards and the unknown spectra (RMS error).Finally, some aspects of the chemical, spectroscopic (UV, IR) and thermoanalytical (TG, DSC) behaviour of gamma-oryzanol and the values of the parameters which enable "computation" of its UV spectra are reported.     

Comparison of three methods for the determination of the electrical conductivity of ion-exchange polymers

The development of ion-exchange membranes techniques using an electrical potential gradient incite often to define the electrical conductivity of this category of functional polymers. The investigation methods of this conductivity did not stop to vary, to such a point that some results can be contradictory. So we have determined this dynamic characteristic in comparing three recent methods. This has been done with three ion-exchange membranes often used in industrial applications: CM1 and CM2, made from sulfonated and crosslinked polystyrene, and Nafion^® 117 made from sulfonated uncrosslinked polytetrafluoroethylene. Measurements were achieved in sodium chloride solutions, at concentrations from 0.1 to 2 mol l⁻¹. The results show, whatever the polymer microstructure, non-negligible disparities between the three methods.     

New colorimetric and fluorimetric methods for the determination of 1,4-cyclohexanedione

1,4-Cyclohexanedione has been determined by reaction with o-phthalaldehyde in sulfuric acid. The determinations depend on the formation of a dicationic salt of pentacenequinone. A sensitive and highly selective fluorimetric method is recommended, but the reaction can also be used spectrophotometrically. Many organic compounds, as well as the isomers of 1,4-cyclohexanedione, give negative results. A spot test is described which can be used for quick preliminary investigations of complex mixtures for I,4-cyclohexanedione.     

Comparison of three gas chromatography methods for the determination of slip agents in polyethylene films

Polymers require the use of some slip agents, such as oleamide and erucamide, in order to reduce their friction coefficient and to make films easier to handle. In this communication, three analytical methods consisting in pressurized liquid extraction (PLE) and gas chromatography (GC) are used to determine oleamide and erucamide in polyethylene films. The sample was extracted with pure isopropanol (two times) at 105 degrees C for 16 min. Then, the liquid extract containing oleamide and erucamide was analyzed by GC and three different detection systems: flame ionization detector (FID), thermoionic selective detector (TSD) and ion-trap mass spectrometry detector (MSD). Oleamide and erucamide were separated using a 30 m x 0.25 mm (I.D.) 5% phenyl-95% dimethyl-polysiloxane capillary column in 12 min. The chromatographic methods were characterized and compared in terms of repeatability, linearity and sensitivity. The GC-FID and GC-TSD methods were linear up to about 60 microg ml(-1), whereas the linear range for the GC-MSD method was shorter, from 20.5 to 42 microg ml(-1). LODs identified with GC-MSD were two times higher than those identified with the other two methods. Repeatability values (expressed as relative standard deviation) of less than 2.5% were found for FID and TSD but they were above 10% for MSD. Finally, each method was applied to determine the content of erucamide and oleamide in several polyethylene films and the results obtained were compared with those obtained from the nitrogen content measured by pyrolysis and gas-phase chemiluminescence. No significant differences were observed between the results of the methods.     

The colorimetric determination of nickel,chromium, and manganese in steel

With the aid of the Spckkei absorptiometer the colonmetnc delerminations, of nickel (with dimethylglyoxime), chromium (with diphenylcarbazide) and manganese (after oxidation with periodate) in steel were critically sinveyed The following factors were examined. wave length of the light, concentration of the reagents, stability of the coloured solution, temperature, influence of excess non, relation of extinetion coefficient and concentration of the coloured solution, influence of Mo, V, W, Ti, Al, Co, Cu, Ni, Cr, Mn, P and Si.For each determination a recommended procedure is given, with the results of control analyses. The recommended procedures are rapid. They can be used with steels of widely differing composition. The methods are accurate within 5% of the actual Value. 1. NickleAfter neutrahsing the solution 5 ml (01 more) of concentrared ammonia (0.95) must be added. The temperature of the solution must be kept below 30° C before adding the dimethylglyoxime.The extinction coefficient is determined with light of 520 m/gm 2. ChromiumThe chromium is oxidised with hydrogen peroxide in alkaline solution. The influence of iron is ehminated by the addition of phosphoric acid. The recommended acidity is o.2 n, the quantily of diphenylcarbazide is 2 ml of a 1%'s solution in aceton. The determinations are made with a mercury lamp and filter (546 m/gm) 3. ManganeseThe solution of the sampie is boiled with ammoniumpersulphate and then oxidised with 300–500 mg of potassium periodate.The recommended acidity is 2 n, using a mixture of equal parts of sulphuric and phosphoric acids. The determinations are made with light of 520 m/gm.     

A critical evaluation of colorimetric methods for the determination of platinum metals. ii

This paper is the second review of quantitative colorimetric methods for the six platinum metals and covers the period from May, 1953 to March, 1957. Each method is evaluated from the point of view of the optimum concentration range, specified and practical applications to thr assay for platinum metals.     

Trace sulfide determination in oxic freshwaters

A simplified method for determination of reduced sulfur species in natural waters is presented. Reduced sulfur species were separated from a natural water matrix, using purge-and-trap (PT), after reacting with acid (acid volatile sulfide—AVS) or Cr(II) in acidic medium (chromium reducible sulfur—CRS). Sulfide in the trapping medium (0.05 M NaOH), was analyzed spectrophotometrically after derivatization to form methylene blue (MB). AVS precision for Na₂S and zinc sulfide clusters in synthetic solutions was ≤8.5% RSD at concentrations ranging from 48 to 503 nM. Spike recoveries of zinc sulfide clusters were 75-98% in a variety of freshwaters using the AVS procedure. Spike recoveries of Cu sulfide colloids were 94-109% in the same freshwater samples using the CRS procedure. During the analytical procedure an interfering compound was produced due to the reaction of mixed diamine reagent with itself. Lowering the pH of the reaction mixture minimized the formation of this compound. Minimizing contamination from particulates was necessary to achieve sub-nanomolar detection limits. The detection limit for AVS in a 500 ml sample with a 10 cm spectrophotometer cell was 0.1-0.3 nM (3×S.D. blank). The CRS procedure was calibrated with a synthetic CuS colloid. Interferences to the CRS method included finely divided pyrite, polysulfide, thiosulfate, sulfite and some elemental sulfur. The Cr(II) reagent did not reduce sulfate under our experimental conditions. The degree to which zinc sulfide clusters were adsorbed on membrane filters during filtration was mitigated if the clusters were synthesized in the presence of natural organic matter. Examples of AVS and CRS concentrations determined in oxygenated waters using the PT method were comparable to those reported recently by other methods. This method offers greater simplicity than other methods for trace dissolved sulfide determination in natural waters.     

Fast Navy 2 R as a colorimetric reagent for the determination of copper, manganese and zinc

Summary Solochrome Fast Navy 2R has been found to be a suitable colorimetric reagent for the determination of copper, manganese and zinc either in pure solutions or in mixtures. The range of determination varies between 0.5–4 g/25 ml. Study of the effect of time, temperature, p_H on the determination was carried out. The molecular ratio of the dyemetal complex was investigated using the slope ratio method.Tables for the various determination are given and show that the experimental errors are of satisfactory order. Good results were obtained by the use of EDTA, cyanide or thioglycollic acid to mask the various interfering cations.

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Zusammenfassung Solochrome Fast Navy 2R wird zur colorimetrischen Bestimmung von Kupfer, Mangan und Zink in reinen Lösungen oder in Mischungen empfohlen. Die erfaßbaren Mengen liegen im Bereich zwischen 0,5 und 4 g/25 ml. Die Genauigkeit der Ergebnisse ist befriedigend. Der Einfluß der Zeit, der Temperatur und des p_H-Wertes sowie das Molverhältnis im Metall-Farbstoff-Komplex wurden untersucht. Verschiedene störende Kationen konnten erfolgreich mit ÄDTA, Cyanid oder Thioglykolsäure maskiert werden.

     

Comparison of methods for the determination of vanadium in sea-water

Procedures for the determination of vanadium in sea-water have been independently developed at two laboratories. The separation and concentration steps were distinctly different and quantification was by neutron activation or atomic absorption. Both methods provide a reliable measurement of vanadium concentration at natural levels in sea-water.     

Comparison of methods for the determination of fluorine in plants

Summary The determination of fluorine in plant material has been carried out by potentiometry using an ion-specific electrode. The decomposition of the material has been performed by the oxygen flask combustion, by NaOH fusion or by leaching with nitric acid. Both the first mentioned procedures are accurate and show the same precision, the first one being less time-consuming. Other methods have been found to be unnecessarily complicated.

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Vergleich von Methoden zur Fluorbestimmung in Pflanzen

Zusammenfassung Die Bestimmung wurde potentiometrisch mit Hilfe einer ionenspezifischen Elektrode durchgeführt. Der Aufschluß erfolgte durch Verbrennung im Sauerstoffkolben, Schmelze mit NaOH oder Auslaugen mit Salpetersäure. Die beiden erstgenannten Verfahren erwiesen sich als die genauesten und zeigten gleiche Reproduzierbarkeit, wobei die Verbrennung im Sauerstoffkolben weniger zeitaufwendig ist. Andere Methoden sind unnötig kompliziert.

     

A new method for the evaluation of the oxidizing equivalent of manganese in surface freshwaters

The suitability of application of a number of previously used methods for the evaluation of the oxidizing equivalent (OE) of manganese in natural waters is compared with a new method, which depends upon colour development of the dye N,N'-diethyl-p-phenylenediamine (DPD) upon oxidation by oxidized forms of manganese. The effect of introducing a commonly used metabolic poison, azide, into the most reliable of these determinations of OE has also been assessed.     

Rapid colorimetric determination of manganese in waters containing iron : A modification of the formaldoxime method

A rapid photometric method with formaldoxime is described for the determination of small amounts of manganese in waters containing iron. The iron formaldoxime formed is decomposed by addition of EDTA and hydroxylamine after development of the manganese-formaldoxime color. Beer's law holds up to 3 mg Mn/1. Up to 25 mg iron(II) or (III) per 1 can be tolerated.     

Comparison of activation methods for mercury determination

A comparative study is made on different activation methods for mercury analysis. Mercury concentrations down to 0.1 ppm were determined instrumentally via the isotopes¹⁹⁷Hg (T=65 h) and²⁰³Hg (T=47 d). A high-resolution Ge(Li) detector was used in measuring the activity and a small computer for data reduction. Up to 500 samples were measured daily. Chemical separations were performed on samples with low mercury concentrations. Sensitivity of 0.01 ppm was attained by precipitating HgS from basic solutions and counting¹⁹⁷Hg on NaI(T1) detector. A new rapid instrumental method was also developed based on^199mHg (T=43 min). This short-lived isotope was activated with resonance neutrons. The sensitivity of the method is 0.5 μg and it requires only 1 hr.     

Oxidants for the colorimetric determination of pindolol

A simple, sensitive and accurate colorimetric method is described for the quantitative determination of pindolol either in the pure form or in its tablets. The method is based on the oxidation of the indole moiety in pindolol with potassium persulphate or hydrogen peroxide-in acid medium-to give a highly coloured product that exhibits maximum absorption at 535 nm and 570 nm, respectively. Beer's law is obeyed over concentrations ranging from 0.07-0.35 mg/10 ml for potassium persulphate and 0.1-0.5 mg/10 ml for hydrogen peroxide with mean recoveries of 99.6+/-0.6 and 99.8+/-0.9%, respectively. The method is applied for the assay of pindolol tablets without any interference due to tablet fillers.     

Comparison of three methods for natural gas dehydration

This paper compares three methods for natural gas dehydration that are widely applied in industry:(1) absorption by triethylene glycol, (2) adsorption on solid desiccants and (3) condensation. A comparison is made according to their energy demand and suitability for use. The energy calculations are performed on a model where 105 Nm3/h water saturated natural gas is processed at 30 °C. The pressure of the gas varies from 7 to 20 MPa. The required outlet concentration of water in natural gas is equivalent to the dew point temperature of -10 °C at gas pressure of 4 MPa.     

The application of the MBTH method for carbohydrate determination in freshwaters revisited

There is a lack of reliable and easy-to-use methods for the quantitative determination of carbohydrates in natural waters. Among the existing methods, the 3-methyl-2-benzothiazolinone hydrochloride (MBTH) method has been widely used to determine total dissolved carbohydrates in seawater. Its application to freshwaters has, so far, been less frequent. The objective of this study is to critically examine the application of the MBTH method to the analysis of carbohydrates in freshwater samples in order to understand what the method really measures. Following a comprehensive revision of the literature, the method has first been applied to representative model compounds and then to a variety of freshwaters of contrasting trophic characteristics. By simultaneously determining the total dissolved organic carbon and humic-type compounds in the same samples, it has been possible to show that sometimes a significant part of the organic carbon remains undetected. This seems to indicate that a substantial amount of carbohydrate present in some natural waters is probably not ‘seen’ by the MBTH method.