F. Bermejo-Martinez

Determination of vanadium in water by electrothermal atomisation atomic absorption spectrometry after extraction with 8-hydroxyquinoline in isobutyl methyl ketone

A sensitive method for the determination of vanadium in water by electrothermal atomisation atomic absorption spectrometry (ETAAS) is described. The vanadium is chelated with 8-hydroxyquinoline in isobutyl methyl ketone and determined by ETAAS after pre-heating the pyrolytic graphite coated graphite tube of a graphite furnace atomiser before injection. The effects of the pH and amount of reagent required for the extraction were studied. The precision, accuracy and interferences of the method were also investigated. The proposed method allows concentrations of vanadium of 0.16 microgram l-1 to be detected.

Spectrophotometric determination of bismuth in pharmaceutical preparations using mucic acid

The formation of a 1 : 1 complex with mucic acid (MuH6) has been used for the determination of concentrations of 4.5–25.5 p.p.m. of bismuth(III) at pH 4.0–5.0. The complex exhibits maximum absorption at 245 nm, with a molar absorptivity of 6.5 × 103 l mol–1 cm–1. The method is specific and was applied to the determination of bismuth in pharmaceutical preparations.

Determination of molybdenum with gallic acid and hydroxylamine

A method for the spectrophotometric determination of molybdenum with gallic acid and hydroxylamine is proposed. The spectrum of the complex formed has a stable absorption maximum at 420 nm in acidic media and the molar absorptivity is 4.84 × 103 l mol–1 cm–1 in the range in which the complex obeys Beers law (3.02–25.12 µg ml–1 of Mo). The effects of the concentration of reagent, pH, time and temperature were investigated, together with the stoicheiometry of the complex, the reproducibility and precision of the method and its susceptibility to interferences.

Spectrophotometric determination of arsenic with diethyldithiocarbamic acid silver salt and borohydride as reducing agent

Abstract A modification of the Vasak and Sedivec method for the spectrophotometric determination of arsenic using borohydride as reducer was proposed. The absorption spectrum, fulfilment of Beers Law, interval of application, and reproducibility of the method were all examined. Statistical and economic studies of the method were carried out. It is proposed that this method be applied in the determination of arsenic in soils.

Chemical modifiers in the determination of molybdenum in human serum by electrothermal atomic absorption spectrometry

SummaryVarious modifiers were investigated for the molybdenum determination in human serum samples by electrothermal atomization atomic absorption spectrometry. Methods with magnesium nitrate, barium difluoride, nitric acid, palladium-magnesium nitrate and palladium-hydroxylamine were studied by introducing the serum samples directly into the graphite furnace with 0.2% triton X-100. The mineralisation and atomization curves, the amount of modifier and the calibration and addition graphs were studied in all instances. The characteristic masses were 18, 22, 17, 12 and 13 pg of molybdenum for magnesium nitrate, barium difluoride, nitric acid, palladium-magnesium nitrate and palladium-hydroxylamine, respectively. The precision, accuracy and interferences of the methods were also investigated.

Spectrophotometric determination of vanadium(V) with oxine in isoamyl alcohol

Abstract A new method for the spectrophotometric determination of vanadium(V) with 8-hydroxyquinoline in isoamyl alcohol is described. The spectra show broad absorption maxima between 450 and 490 nm. The effects of amount of reagent, acidity, time, and temperature were also studied. The optimal interval of Beers law application is 0.75–3.50 μg vanadium/ml. The nature of the complex in solutions, as well as the interference, reproducibility, and precision of the method, was investigated. The method has been applied to the determination of vanadium in foods.

Determination of traces of molybdenum in foods by electrothermal atomic absorption spectrometry

Abstract Low levels of molybdenum in different food samples were determined by atomic absorption spectrometry with electrothermal atomization after destruction of organic matter using four different methods, involving dry ashing at 600°C, wet digestion with heating with nitric/sulphuric and nitric/sulphuric/perchloric acid mixtures or direct extraction with dilute hydrochloric acid. In all cases the working conditions, reproducibility, precision and accuracy were investigated. The dry ashing method was generally the optimum destruction method.

Simultaneous derivative spectrophotometric determination of iron(III) and bismuth(III) with EDTA

The application of derivative spectrophotometry to the simultaneous determination of iron(III) and bismuth(III) with EDTA is described. The procedure developed does not require the solution of systems of equations and is suitable for concentrations of 0.5–8.0 µg ml–1 of iron(III) and 0.1–35.7 µg ml–1 of bismuth(III). The interferences, whether by anions or cations, are easily eliminated.

Extraction-spectrophotometric determination of molybdenum with toluene-3,4-dithiol

A spectrophotometric method for the determination of molybdenum(VI) with toluene-3,4-dithiol in isobutyl methyl ketone is proposed. In acidic media the spectrum of the complex formed has a stable absorption maximum at 415 nm with a molar absorptivity of 7.5 × 104 l mol–1 cm–1 in the range of optimum compliance with Beers law, 0.25–1.25 µg ml–1 of Mo. The effects of the concentration of reagent, acidity, time and temperature are reported, together with the reproducibility and precision of the method, its susceptibility to interferences and its application to the determination of molybdenum in steel.

Spectrophotometric study of bismuth with N-(2-acetamido)iminodiacetic acid (ADA): Determination of bismuth in pharmaceutical formulations

Abstract A new method for the Spectrophotometric determination of bismuth using N-(2-acetamido)iminodiacetic acid as complexometric agent is proposed. The complex is formed in a wide pH range, 5.5–7.5, and has a maximum absorption at 265 nm. Beers law is obeyed in the interval 3.8–17.9 μg of bismuth(III)/ml, with a minimum photometric error of 2.3. The molar absorptivity is 9.1 × 103 liters/cm mol. The stoichiometry of the reaction takes place in the metal-to-ligand ratio 1:2. The interferences produced by the more common ions are studied. The method has been successfully applied to the determination of bismuth in pharmaceutical formulations.