Rapid spectrophotometric determination of chromium(III)

A spectrophotometric procedure is suggested for the determination of Cr(III). The reaction between Cr(III) and 2-(5-bromo-2-pyridylazo)-5-dimethylaminophenol is accelerated by sodium dodecyl sulphate(SDS), sodium benzoate causes a further increase in the absorbance of the chelate. The optimum pH range for the reaction is 5-5.8(benzoate buffer). The chelate exhibits maximum absorbance at 590 nm, obeys Beer's law over the concentration range 0.02-0.56 microg/ml of Cr(III), has molar absorptivity of 7.8 x 10(4) 1. mol(-1) cm(-1) and a Sandell sensitivity of 0.66 ng/cm. The metal to ligand ratio is 1:2 in the absence of SDS and 1:1 in its presence. A procedure for the determination of Cr(III) and Cr(VI), when present together, is described. The method has been applied to the analysis of Cr(III) in tap water.     

Sensitive spectrophotometric determination of molybdenum(VI) with Pyrogallol Red and cetyltrimethylammonium ions

Pyrogallol red in the presence of cetyltrimethylammonium bromide is proposed for the spectrophotometric determination of microgram amounts of molybdenum. The sensitivity of the color reaction between molybdenum and Pyrogallol Red has been greatly increased by the sensitizing action of cetyltrimethylammonium bromide (?_{600 nm} = 90,000). Beer's law is obeyed over the range 0.1–0.4 μg/ml of molybdenum. The composition of the complex may therefore be formulated as Mo:PR:CTA = 1:2:4.     

Flow-injection spectrophotometric determination of molybdenum and vanadium with carminic acid in the presence of cetyltrimethylammonium bromide

The color-forming reactions of molybdenum(VI) and vanadium(IV) with carminic acid (CA) in the presence of cetyltrimethylammonium bromide (CTAB) were used in the flow-injection determination of these metals. The micellar medium enhances the spectrophotometric features of the Mo(VI)-CA and V(IV)-CA binary complexes, and the higher solubility of these complexes when the CTAB concentration is above critical micelle concentration permits the easy application of flow-injection systems. Under the optimum conditions, linear calibration graphs were obtained from 0.76 to 28.8 g/ml for molybdenum and from 0.30 to 9.1 g/ml for vanadium. The detection limits were 0.33 and 0.16 g/ml for molybdenum and vanadium, respectively. The selectivity of the method was investigated and the procedure was successfully applied to the determination of molybdenum in steels and pharmaceuticals and of vanadium in petroleum products.     

Titrimetric determination of microgram amounts of thallium(I) by thiocyanate amplification after precipitation as thallium hexathiocyanatochromate(III)

Summary Thallium (5–200g) is precipitated as Tl₃Cr(SCN)₆. The precipitate is collected, then treated with 10% sodium carbonate solution, and the thiocyanate dissolved is oxidized to sulphate by iodine at pH 8.2. After acidification, the excess of iodine is extracted into chloroform, and the iodide in the aqueous solution is determined by the Leipert amplification procedure. The method provides 76 iodine atoms for each original thallium(I) ion. Copper(II), mercury(II), bismuth, lead and silver interfere seriously, the first three causing negative errors and the other two positive errors.

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Maanalytische Bestimmung von Mikrogrammengen Thallium(I) durch Vervielfachung mit Thiocyanat nach Fällung als Thalliumhexathiocyanatochromat(III)

Zusammenfassung Thallium (5–200g) wird als Tl₃Cr(SCN)₆ gefällt. Der gesammelte Niederschlag wird mit 10% iger Sodalösung behandelt und das gelöste Thiocyanat mit Jod bei pH 8,2 zu Sulfat oxydiert. Nach Ansäuern wird der Jodüberschuß mit Chloroform extrahiert und das Jodid in der wäßrigen Lösung nach Leipert titriert. Dabei entsprechen 76 Jodatome einem ursprünglichen Thallium(I)ion. Cu(II), Hg(II), Bi, Pb und Ag stören stark und verursachen negative bzw. im Falle Pb und Ag positive Fehler.

     

Extractive spectrophotometric determination of trace amounts of iron(III) with benzyltriethylammonium chloride

The ion-association complex formed between a thiocyanato-iron(III) ion and a benzyltriethylammonium ion is extracted into 1,2-dichloroethane, and its absorbance at 476 nm is used for determination of the iron. Beer's law is obeyed up to about 4 mug/ml iron concentration in the final solution. The molar absorptivity is 2.79 x 10(4) l.mole(-1).cm(-1).     

Rapid and sensitive spectrophotometric determination of trace amounts of iron(III) using leuco Xylene cyanol FF

A new, simple, sensitive, and reliable method is presented for the rapid spectrophotometric determination of trace amounts of iron(III) using leuco Xylene cyanol FF. The method is based on the oxidation of leuco Xylene cyanol FF (LXCFF) to its blue form of xylene cyanol FF by iron(III) in sulfuric acid medium (pH 2.0–3.0), the absorbance of the formed dye is measured in an acetate buffer medium (pH 2.8–4.4) at 615 nm. The method obeys Beer's law over a concentration range of 0.15–0.9 g mL^-1 iron, having a molar absorptivity of 5.6×10⁴ L mol^-1 cm^-1 and a Sandell's sensitivity of 0.0001 g cm^-2. The optimum reaction conditions and other analytical parameters have been evaluated. The developed method has been successfully applied to the determination of iron in water, soil, industrial effluent, plant material, pharmaceutical preparations, synthetic mixtures, and aluminum alloys.     

Voltammetric determination of ciprofloxacin based on the enhancement effect of cetyltrimethylammonium bromide (CTAB) at carbon paste electrode

Herein, an electrochemical method was developed for the determination of ciprofloxacin based on the enhancement effect of cetyltrimethylammonium bromide (CTAB). In pH 7.0 phosphate buffer, a poorly-defined oxidation peak is observed at carbon paste electrode (CPE) for ciprofloxacin. However, the oxidation peak current remarkably increases in the presence of low concentration of CTAB, suggesting that CTAB exhibits obvious enhancement effect to the determination of ciprofloxacin. All the experimental parameters, such as supporting electrolyte, pH value, concentration of CTAB, and accumulation time, were optimized for ciprofloxacin analysis. This new method possesses high sensitivity (detection limit is 5.0 × 10⁻⁸ mol l⁻¹), wide linearity (1.0 × 10⁻⁷−2.0 × 10⁻⁵ mol l⁻¹), rapid response, low cost and simplicity. Finally, this method was successfully employed to detect ciprofloxacin in drugs. The text was submitted by the authors in English.     

Lamellar phases in mixtures of low molecular weight alkanols and cetyltrimethylammonium bromide (CTAB)

Partial phase diagrams showing the domains of existence of a transparent, viscous, lamellar-structured (D)-phase that transforms reversibly into fluid single phase solutions at high temperature are presented for the system: cetyltrimethylammonium bromide (CTAB), two low molecular weight alcohols, and water with and without additives. At constant temperature and with a fixed amount of surfactant, the size and location of this phase in the phase diagram depends upon three composition variables: i) the ratio of concentrations of medium chain alcohol to long chain alcohol (R), ii) the ratio of concentrations of medium chain alcohol to surfactant (R), and iii) the concentrations of small amounts (up to 10 % by weight) of additives such as ethylene glycol, propylene glycol, and dimethylformamide, as well as NaBr. Small-angle x-ray scattering measurements of these mixtures reveal a lamellar structure. The observed lamellar repeat distances range from 60 A to 290 Å and depend upon the ratiosR andR and the concentration of the additives. The mechanical and structural properties of theseD-phases can be tuned by adjustingR andR. TheD-phase-to-isotropic transition temperature can be varied from near room temperature to above 80 °C by adjustingR andR.     

The determination of magnesium in the presence of large amounts of zinc: A spectrophotometric method

The spectrophotometric determination of magnesium in the presence of large amounts of zinc is described. Zinc as well as some other interfering metals are removed by mercury cathode electrolysis and aluminium is removed by a chloroform extraction with 8-hydroxyquinoline.     

Rapid extraction and direct spectrophotometric determination of iron(III) with thiothenoyltrifluoroacetone

To obtain NH₄F-HF etching agents with constant etching behaviour the concentration of NH₄OH in commercially available 40% NH₄F solutions has to be measured. By application of pH-indicators of the phenol type very small pH-deviations (0.007 pH) from the specified value (0% NH₄OH) can be measured. The specified value is simulated by the stable McIlvaine buffer. By determining the differences in optical absorption 0.01% NH₄OH can be measured in NH₄F solutions. Values found in practice are between 0.1– 0.3%.     

Fluorescence enhancement of yttrium(III)-rutin by nucleic acids in the presence of cetyltrimethylammonium bromide

It is found that nucleic acids can enhance the fluorescence intensity of yttrium(III) (Y(3+))-rutin in presence of cetyltrimethylammonium bromide (CTMAB) system. In hexamethylenetetramine (HMTA)-HCl buffer, the maximum enhanced fluorescence is produced, with maximum excitation and emission wavelengths at 452 and 520 nm, respectively. Based on this, a new fluorimetric method of determination of nucleic acids is proposed. Under optimum conditions, the enhanced fluorescence intensity is proportion to the concentration of nucleic acids in the range of 1.0 x 10(-7) to 1.0 x 10(-5)g/ml for fish sperm DNA (fsDNA), 1.0 x 10(-7) to 4.6 x 10(-6)g/ml for yeast RNA (yRNA), their detection limits (S/N=3) are 7.5 x 10(-8), 8.0 x 10(-8)g/ml, respectively. The interaction mechanism is also studied.     

Rapid spectrophotometric determination of ruthenium(III) with prochlorperazine maleate

A rapid, simple spectrophotometric method for the determination of μg amounts of ruthenium, based on the formation of a pink complex between the metal and prochlorperazine maleate (PCPM) in sulphuric or hydrochloric acid solution, is described. The complex has an absorption maximum at 530 nm and its molar absorptivity is 6.733·10³ l mol^?1 cm^?1. The sensitivity is 0.0151 μg Ru cm^?2 for log I_o/I = 0.001. Beer's law is valid over the range 0.2–10 μg Ru ml^?1 ; the optimal range for spectrophotometric determination is 0.8–8.0 μg Ru ml^?1. Job's method of continuous variation, the mole ratio method and the slope ratio method indicate a 1:1 composition for the complex. The effects of acidity, time, temperature, order of addition of reagents, reagent concentration, and the interferences from various ions are reported.     

Spectrophotometric determination of aluminium with Chromal Blue G in the presence of cetyltrimethylammonium chloride

Summary Spectrophotometric Determination of Aluminium with Chromal Blue G in the Presence of Cetyltrimethylammonium Chloride Chromal Blue G (C. I. 43835) in the presence of cetyltrimethylammonium chloride is proposed for the spectrophotometric determination of microgram amounts of aluminium. The stoichiometric ratio of aluminium to Chromal Blue G is 14. Beer's law is obeyed from 0.01 to 0.16 ppm of aluminium. The molar absorptivity is 1.62×10⁵1·mole^–1·cm^–1 at 660 nm.     

Spectrofluorometric determination of trace amounts of terbium with 4-chlorosalicylic acid, EDTA, and cetyltrimethylammonium bromide.

The quadruple complex formed by terbium with 4-chlorosalicylic acid (CSA), EDTA and cetyltrimethylammonium bromide (CTMAB) has been used for the sensitive spectrofluorometric determination of terbium in mixed rare earths. The effect of the experimental conditions on the fluorescence intensity was defined. Under the optimum conditions selected, the fluorescence intensity was linear with the terbium concentration in the range of 3.0 x 10(-8)-1.0 x 10(-5) mol/L with a detection limit of 8.0 x 10(-9) mol/L (S/N = 3). It has been satisfactory for the determination of terbium in mixed rare earths with good recovery.     

Titrimetric determination of microgram amounts of lead by thiocyanate amplification after precipitation as lead hexathiocyanatochromate(III)

Lead (25–200 μg) is precipitated as Pb₃[Cr(SCN)₆]₂. The filtered precipitate is treated with 10% carbonate solution, and the thiocyanate dissolved is oxidized by iodine to sulphate at pH 8.2. After acidification, the excess of iodine is extracted into chloroform, and the iodide ion retained in the aqueous solution is amplified by bromine oxidation and subsequent treatment with more iodide. The method provides 152 iodine atoms for each original lead ion. Only Bi³⁺ and Cu²⁺ interfere seriously.