Simultaneous spectrophotometric determination of molybdenum and selenium,and of molybdenum and tellurium

A method is reported for the extraction of molybdenum-phenylfluorone by chloroform. The extraction is complete whether perchlorate ions are present or not but the extractions in the presence of perchlorate ions gave a somewhat more sensitive procedure for the spectrophotometric determination of molybdenum in the solvent phase as the molybdenum-phenylfluorone complex.A procedure is reported for the simultaneous determination of molybdenum and selenium, and molybdenum and tellurium. The method involves first the formation and solvent extraction of the molybdenum-phenylfluorone complex by chloroform in the presence of perchlorate ions, followed by determination of selenium in the remaining aqueous phase as selenium-diethyldithiocarbamate complex after solvent extraction with 2-ethyl-1-hexanol in the presence of perchlorate ions. A similar procedure is reported for the simultaneous determination of molybdenum and tellurium except that in the determination of molybdenum, the phenylfluorone complex is extracted by chloroform in the absence of perchlorate ions. Tellurium is determined in the remaining aqueous phase as tellurium-diethyldithiocarbamate complex after solvent extraction by 2-ethyl-1-hexanol solvent extraction in the presence of perchlorate ions.     

Selective stripping voltammetric determinations employing cells for electrolysis with simultaneous ion-exchange or solvent extraction

Cells have been designed for stripping-voltammetry analyses employing graphite working electrodes and mercury film electrodes on a graphite support, permitting ion-exchange or solvent extraction separation simultaneously with the pre-electrolysis. The ion-exchange separation was tested on the determination of mercury in the presence of excess of copper(II), lead and cadmium and on the determination of bismuth in the presence of excess of copper(II). The solvent extraction separation was tested on the determination of mercury(II) in the presence of copper(II), lead and cadmium and the determination of copper(II) in the presence of bismuth. Very good results were obtained by using ion-exchange, where the sensitivity and precision of the determination are comparable with those obtained in the determinations without separation, the separation efficiency being very high, limited virtually only by the capacity of the ion-exchanger used. The solvent extraction separations yielded poorer results: the sensitivity of the determination is decreased substantially, the separation efficiency is not very high and difficulties arise from the adsorption of the organic phase on the electrode surface.     

Determination of Epoxy and Isocyanate Groups in the Presence of Each Other

Analytical reactions for the determination of epoxy and isocyanate groups in the presence of each other in epoxy–isocyanate compositions were studied. For the determination of epoxy groups in the presence of isocyanate groups, a test with HBr in glacial acetic acid was proposed; acetic acid reacts with isocyanate groups and, hence, masks them. Isocyanate groups in the presence of epoxy groups were determined by potentiometric titration with a solution of piperidine in ethyl methyl ketone. The addition of toluene to the test solution decreases the fraction of the enol form of ethyl methyl ketone, which interferes with the determination.     

Simultaneous determination of tin and lead by a.c. anodic stripping voltammetry at a hanging mercury drop electrode sensitized by cetyltrimethylammoniu

The influence of cetyltrimethylammonium bromide (CTAB) on the simultaneous determination of tin(IV) and lead(II) by anodic stripping voltammetry at a hanging mercury drop electrode (HMDE) in a 0.1 M hydrochloric acid—0.1 M oxalic acid medium was studied using d.c. and a.c. stripping. In the presence of CTAB, tin and lead show voltammetric peaks separated by 100 mV, the sensitivity depending on the concentration of CTAB. The best conditions for the simultaneous determination of both elements (2 × 10^-3 M) were found. A method is proposed for the determination of tin in the presence of lead and three procedures are given for the determination of lead in the presence of tin.     

How faster and cheaper to determine chromium by adsorptive cathodic stripping voltammetry in the presence of DTPA and nitrate

A modification of the voltammetric procedure for the determination of chromium in the presence of DTPA and nitrates was proposed. Morpholinoethanesulfonic (MES) acid and its sodium salt were used for stabilisation of pH instead of acetate buffer. In the presence of MES the determination of chromium can be carried out in the presence of dissolved oxygen without decrease of sensitivity of the measurements. Elimination of the purge step decreases total analysis time and saves gas.     

Determination of Epoxy Groups in the Presence of Carboxylic Acids of the Acryl Series and Aromatic Amines

Selective reactions for the determination of epoxy groups in the presence of acrylic acids and aromatic amines were studied. Factors affecting results of the determination of epoxy groups were revealed. Procedures were developed for the determination of epoxy and carboxylic groups and epoxy and amine (aromatic) groups in the presence of each other. The reaction is conducted in excess HCl in the former case and in excess tetraethylammonium bromide in the latter case. Performance characteristics of the procedures were estimated.     

Effect of plutonium on the potentiometric determination of uranium

Effect of the presence of plutonium on the determination of uranium by potentiometric method has been studied. The presence of large quantities of plutonium does not appear to affect the determination of uranium present at 5 mg as well as 250 mg levels.     

How faster and cheaper to determine chromium by adsorptive cathodic stripping voltammetry in the presence of DTPA and nitrate

A modification of the voltammetric procedure for the determination of chromium in the presence of DTPA and nitrates was proposed. Morpholinoethanesulfonic (MES) acid and its sodium salt were used for stabilisation of pH instead of acetate buffer. In the presence of MES the determination of chromium can be carried out in the presence of dissolved oxygen without decrease of sensitivity of the measurements. Elimination of the purge step decreases total analysis time and saves gas.     

Extractive photometric determination of vanadium with catechol and a tertiary amine

Metal catechol complexes can be extracted from aqueous solution with chloroform in the presence of tertiary amines, for example diphenylguanidine, tributylamine or collidine. Collidine can also be used for the determination of vanadium, titanium, molybdenum and niobium in the presence of a small amount of iron or tantalum. The method for determination of microgram amounts of vanadium is described.     

Potentiometric titration of peptides and the starting materials and intermediates of their synthesis. I. Acidimetric determination of N-acetylamino acids

The potentiometric titration of N-acetylamino acids and their sodium salts in nitromethane-acetic anhydride (2:1) with a nitromethane solution of perchloric acid has been investigated. A procedure has been developed for the quantitative determination of N-acetylamino acids in the presence of acetic acid in aqueous solutions. A differentiation determination of N-acetylamino acids and their salts in the presence of sodium acetate has been carried out.     

Kinetic spectrophotometric determination of Fe(II) in the presence of Fe(III) by H-point standard addition method in mixed micellar medium

The H-point standard addition method was applied to kinetic data for simultaneous determination of Fe(II) and Fe(III) or selective determination of Fe(II) in the presence of Fe(III). The method is based on the difference in the rate of complex formation between iron in two different oxidation states and methylthymol blue (MTB) at pH 3.5 in mixed cetyltrimethylammonium bromide (CTAB) and Triton X-100 micellar medium. Fe(II) can be determined in the range 0.25-2.5 microg ml(-1) with satisfactory accuracy and precision in the presence of excess Fe(III) and other metal ions that rapidly form complexes with MTB under working condition. The proposed method was successfully applied to the simultaneous determination of Fe(II) and Fe(III) or selective determination of Fe(II) in the presence of Fe(III) in spiked real environmental and synthetic samples with complex composition.     

New colorimetric method for the determination of nystatin

A new colorimetric method for the determination of nystatin is reported, based on the reaction of the alkaline hydrolysis product of nystatin with p-aminoacetophenone in presence of concentrated hydrochloric acid. The proposed method determines 0.2-1.0mg of nystatin with recovery of 100.7 +/- 1.2%. The method is adopted to the determination of nystatin in pharmaceutical preparations, and interference due to the presence of sugar is eliminated.     

Determination of trimethoprim by the linear absorbances method

The determination of trimethoprim in the presence of dyphylline, proxyphylline, theophylline and caffeine by the linear absorbances method is described. Collinear couples of wavelengths, for the interfering dyphylline-proxyphylline-theophylline-caffeine system (in H₂SO₄, 0.05 mol/L), are provided in order to allow the determination of the analyte in the presence of these interfering substances.     

Sorption-spectrometric determination of thorium(IV) and uranium(VI) with the reagent Arsenazo III on the solid phase of a fibrous material filled with a cation exchanger

The possibility of the use of organic reagents of the Arsenazo III group for the sorption-spectrometric determination of elements on fibrous cation-exchange materials was examined. The conditions of the sorption of Arsenazo III with the use of diphenylguanidinium chloride on the strongly acidic fibrous cation exchanger PANV-KU-2 were found. Procedures for the determination on the solid phase were developed for thorium in 7 M HNO₃ in the presence of 30-fold amounts of uranium with the detection limit of thorium of 0.005 μg/mL and for uranium in 0.05 M HCl in the presence of fivefold amounts of thorium with a detection limit of uranium of 0.05 μg/mL. The conditions were found for the selective preconcentration of thorium and uranium in the presence of each other, and a procedure was developed for their separate sorption-spectrometric determination.     

Die selektive invers-voltammetrische Bestimmung des Antimons in salzsauren L?sungen nach L?sungswechsel in einer einfachen Durchflu?zelle

Summary The selective invers-voltammetric determination of antimony in a simple flow-through cell in hydrochloric acid solutions is described. After double medium exchange for post-electrolysis and inverse-voltammetric determination, the determination of antimony is possible in the presence of a large excess of copper, bismuth and other elements. The limit of determination is 0.2–0.3 ppb Sb, the reproducibility 1.5% (10 ppb Sb).     

Determination of traces of free acid in uranyl salt solutions

A method for the determination of free acid in the presence of uranium(VI) is suggested. It involves the extraction of uranium by TBP from a solution saturated with potassium nitrate or chioride in order to prevent interference from the hydrolysis of uranium. The end-point is detected potentiometrically at pH 3.4. The method is suitable for the determination of 0.1–1.5 millimoles of acid in the presence of as much as 1.0 millimole of uranium.     

Katalytische bestimmung von silberspuren in wabetariger lösung und nach extraktion

The application of the catalysed oxidation of Bromopyrogallol Red by potassium per- sulphate for silver determination is discussed. In aqueous solution silver concentrations of 0.5- 1 mug/ml can be determined and 1- 13 ng/ml in the presence of 1, 10-phenanthroline as activator. In combination with solvent extraction, catalytic determination of the extracted silver is possible even in presence of 200 mug of iron(III), cobalt(II) and palladium(II). By means of an automatic variant of the simultaneous comparison method a more sensitive determination (0.2-20 ng/ml) was achieved.     

Über die verteilung von metall-8-oxychinolin-verbindungen zwischen wasser und organischen lösungsmitteln : Mitt. photometrische bestimmung des magnesiums nach extraktion seines oxinates mit chloroform bei gegenwart von aminen

Under normal conditions, magnesium oxinate does not dissolve in non-polar organic solvents. In the presence of 2% butyl amine, however, magnesium can be extracted quantitatively in the pH range 10.5–13.6 by a 0.1% oxine-chloroform solution (concentration range 0.05–10γ Mg/ml), and can be determined photometrically by measurement of the extinction at 380 mμ. This reaction has been elaborated to a specific method of determination for small quantities of magnesium in the presence of the most important other elements. Furthermore, determination of magnesium can be combined quite simply with a photometric determination of slight iron content, also as the oxinate. The practical application of the method is demonstrated by determination of magnesium and iron in several calcium minerals, aluminium alloys and a zinc alloy.     

Simultaneous kinetic determination of Fe(III) and Fe(II) by H-point standard addition method

The H-point standard addition method (HPSAM) was applied to kinetic data for simultaneous determination of Fe(III) and Fe(II) or selective determination of Fe(III) in the presence of Fe(II). The method is based on the difference in the rate of two processes; reduction of Fe(III) with Co(II) and subsequent complex formation of resulted Fe(II) with 1,10-phenanthroline, and direct complex formation between Fe(II) and 1,10-phenanthroline in pH 3 and cetyl trimethyl ammonium bromide, CTAB, micellar media. Fe(III) can be determined in the range of 0.75-5.13 mug ml(-1)with satisfactory accuracy and precision in the presence of excess Fe(II) under working conditions. The proposed method was successfully applied to the simultaneous determination of Fe(III) and Fe(II) and also to the selective determination of Fe(III) in the presence of Fe(II) in several synthetic mixtures containing different concentration ratios of Fe(III) to Fe(II).     

Determination of bismuth and copper using adsorptive stripping voltammetry couple with continuous wavelet transform

A new method is proposed for the determination of bismuth and copper in the presence of each other based on adsorptive stripping voltammetry of complexes of Bi(III)-chromazorul-S and Cu(II)-chromazorul-S at a hanging mercury drop electrode (HMDE). Copper is an interfering element for the determination of Bi(III) because, the voltammograms of Bi(III) and Cu(II) overlapped with each other. Continuous wavelet transform (CWT) was applied to separate the voltammograms. In this regards, wavelet filter, resolution of the peaks and the fitness were optimized to obtain minimum detection limit for the elements. Through continuous wavelet transform Symlet4 (Sym4) wavelet filter at dilation 6, quantitative and qualitative analysis the mixture solutions of bismuth and copper was performed. It was also realized that copper imposes a matrix effect on the determination of Bi(III) and the standard addition method was able to cope with this effect. Bismuth does not have matrix effect on copper determination, therefore, the calibration curve using wavelet coefficients of CWT was used for determination of Cu(II) in the presence of Bi(III). The detection limits were 0.10 and 0.05 ng ml⁻¹ for bismuth and copper, respectively. The linear dynamic range of 0.1-30.0 and 0.1-32.0 ng ml⁻¹ were obtained for determination of bismuth in the presence of 24.0 ng ml⁻¹ of copper and copper in the presence of 24.0 ng ml⁻¹ of bismuth, respectively. The method was used for determination of these two cations in water and human hair samples. The results indicate the ability of method for the determination of these two elements in real samples.