Selection of the counter-cation in the solvent extraction of anionic chelates: Spectrophotometric determination of trace amounts of cobalt with 2-nitroso-1-naphthol-4-sulphonic acid and tetrabutylammonium ion

The importance of selecting the most suitable counter-cation in the solvent extraction-spectrophotometric determination of an anionic metal chelate containing a sulphonic acid group is demonstrated and discussed. In the case of cobalt and 2-nitroso-1-naphthol-4-sulphonic acid (nitroso-NW acid), the most suitable counter-cation is the tetrabutylammonium ion (Bu(4)N(+)): in this case only the ion-pair of the anionic cobalt chelate is extracted into chloroform and the excess of the nitroso-NW acid remains in the aqueous phase. The absorption maximum of the chelate in chloroform is at 307nm, at which the molar absorptivity is 6.5 x 10(4)l.mole(-1).cm(-1). The absorbance of the reagent blank at 307 nm is less than 0.010. By use of nitroso-NW acid and Bu(4)N(+), trace amounts of cobalt may be determined in nickel salts and in iron and steel samples.     

Membrane extraction of pertechnetate with quaternary ammonium salts comparison with solvent extraction

The liquid membrane extraction (MX) and the solvent extraction (SX) of pertechnetate with Aliquat 336 as a carrier has been studied. From the results of SX the percentage of pertechnetate in the inner solution in experiment with LM was proposed. It has been found that the pertraction of pertechnetate depends on the inner solution used and the most effective solutions were those with ClO ₄ ^– and SCN^–. Effects of the carrier concentration in membranes and outer phase composition have been studied too. The results of these experiments were kinetic curves with a minimum, which may be interpreted as a result of competing processes in the systems.     

Spectrophotometric determination of tetraphenyl-arsonium salts by solvent extraction with vanadium—par complex

An extraction-visible spectrophotometric method for the determination of tetraphenylarsonium salts is described. The method is based on the extraction of the ion-pair formed between the tetraphenylarsonium cation and the anionic vanadium(V)– 4-(2-pyridylazo)resorcinol complex, followed by the spectrophotometric measurements of the coloured organic phase at 560 nm. The method can be applied to micro amounts of tetraphenylarsonium salt or to very dilute solutions (10^-6 – 10^-5M). It is more sensitive and less subject to interferences than the direct u.v. method.     

Spectrophotometric determination of trace levels of atmospheric ammonia by conversion into indophenol and extraction with quaternary ammonium salts

Indophenol, produced in proportion to the amount of ammonia present, can be quantitatively extracted into chloroform as an ion-pair with tetradodecylammonium (TDA(+)) bromide and determined by spectrophotometry. The molar absorptivity of the indophenol-TDA(+) complex is 2.5 x 10(4) 1.mole(-1).cm(-1) (maximum absorption at 653 nm), which is 25% greater than that for the indophenol-TDA(+) complex in aqueous medium. This procedure is applicable to determination of mul/m(3) levels of atmospheric ammonia, with 1-hr sampling periods.     

Spectrophotometric determination of gallium with 1-(2,4-dihydroxyphenylazo)-2-naphthol-4-sulfonic acid

A new spectrophotometric method for the determination of gallium is described using 1-(2,4-dihydroxyphenylazo) -2-naphthol-4-sulfonic acid (DHPAN) as a reagent. The color reaction has a sensitivity of 0.013 μg Ga per cm² for log 1₀/1=0.005 at 500 mμ and obeys Beer's law up to 2.8 p.p.m. The effects of pH, time, order of addition of the reagents, temperature and diverse ions were investigated. Gallium is separated from interfering ions by solvent extraction.     

Spectrophotometric determination of microgram amounts of penicillins by solvent extraction with azure b

Penicillins are determined by means of ion-pair formation with azure B and extraction into chloroform: the absorbance of the extract is stable for several days. The apparent molar absorptivities for sodium penicillin G and potassium penicillin V at 634 nm are 3.91 × 10³ and 1.25 × 10⁴ l mol^-1 cm^-1, respectively. Calibration graphs are linear over the range 60–950 μg of sodium penicillin G and 40–600 μg of potassium penicillin V in 10 ml. The method is successfully applied to pharmaceutical preparations.     

Spectrophotometric determination of trace amounts of cobalt using 7-Nitroso-8-hydroxyquinoline-5-sulphonic acid as reagent

A thinlayer chromatographic method for the quantitative determination of phthalic acid esters in aqueous PVC-plastic extracts has been developed. Petroleum ether/diethyl ether/glacial acetic acid (8∶2∶0.1) is used as solvent; the plates are coated with 0.2 mm of silica gel with fluorescent agent. After separation and elution a photometric determination is performed.     

The new method for the determination of cobalt in sea water by solvent extraction with 2-nitroso-5-diethylaminophenol

Cobalt in sea waters can be determined spectrophotometrically by means of 2-nitroso-5-diethylaminophenol after extraction of the complex into 1,2-dichloro-ethane. No preliminary concentration is needed. Interferences are prevented by masking or by stripping from the organic phase. The method is applicable over the range 0–0.24 μg Co 1^-1 when 1–1 or 2–1 samples are taken. The relative standard deviation is 4% for 0.15 μg Co 1^-1. The stability of cobalt in sea water samples is discussed.     

Solid-liquid extraction and preconcentration of trace nickel using 2-nitroso-1-naphthol-4-sulfonic acid (Nitroso-S) and TDBA onto benzophenone and determination by atomic absorption spectrometry.

Nickel was quantitatively retained by 2-nitroso-1-naphthol-4-sulfonic acid (Nitroso-S) and tetradecyldimethylbenzylammonium chloride (TDBA Cl) onto benzophenone in the pH range 5.0-6.0 from large volumes of aqueous solutions of various samples. After filtration, each solid mass consisting of a nickel complex and benzophenone was dissolved with 5 ml of dimethylformamide (DMF) and the metal was determined by atomic absorption spectrometry (AAS). About 0.6 microg of nickel could be concentrated from 200 ml of an aqueous sample, where its concentration was as low as 3.0 ng/ml. Eight replicate determinations of 2.5 microg/ml of nickel in the final DMF solution gave a mean absorbance of 0.112 with a relative standard deviation of 1.9%. The sensitivity for 1% absorption was 98 ng/ml. The interference of a number of anions and cations was studied and the developed optimized conditions were utilized for the trace determination of nickel in various alloys and biological samples.     

Spectrophotometric determination of micro amounts of mercury,cadmium, and zinc by stepwise extraction with tribenzylamine

A rapid spectrophotometric method has been developed for the stepwise determination for mercury, cadmium, and zinc in mixtures. Optimal conditions have been established for the extraction efficiency of cadmium and mercury with a chloroform solution of tribenzylamine pre-equilibrated with hydrobromic acid. After addition of dithizone solution to the organic layers the absorbance at 490 nm or 510 nm is measured for mercury or cadmium, respectively. Even when the ratio of mercury, cadmium, and zinc is 10^-1 : 1 : 10^-5 , the metals can be determined successively.     

Solvent extraction of anions with metal chelate cations-XVIII Spectrophotometric determination of maleic acid in the presence of fumaric acid by solvent extraction with tris(1,10-phenanthroline)iron(ii) chelate cations

A new colorimetric method is proposed for the determination of maleic acid. Among aliphatic dicarboxylic acids tested, maleic acid was found to be selectively extracted into nitrobenzene as the red ion-association complex (lambda(max) 516 nm) formed between the hydrogen maleate anion and the tris(1,10-phenanthroline)iron(II) cation. At least a 32-fold molar excess of tris(1,10-phenanthroline)iron(II) relative to maleic acid is needed and the optimal pH range is 3-5. A linear relationship is obtained over the concentration range 10(-5)-10(-4)M maleic acid. The relative standard deviation was 1.0 %. The colour intensity of the extract remains constant at room temperature for at least 24 hr. A large amount of fumaric acid, the trans-isomer of maleic add, is not extracted under the same conditions. This makes it possible to determine maleic acid in the presence of fumaric acid.     

Spectrophotometric determination of iron in sea-water by solvent extraction as the ternary complex iron(II)-2-nitroso-4-chlorophenol-rhodamine B

Iron has been determined in sea-water by extraction of the ternary complex of iron(II) with 2-nitroso-4-chlorophenol and Rhodamine B at pH 4.7 and measurement at 558 nm. Toluene is used as the organic solvent. Any iron(III) is reduced with hydroxylammonium chloride.     

Column preconcentration of trace manganese with the ion pair of 2-nitroso-1-naphthol-4-sulfonic acid tetradecyldimethylbenzyl-ammonium chloride supported on naphthalene and determination by derivative spectrophotometry

A column preconcentration method has been developed for the determination of trace amounts of manganese by preconcentration on 2-nitroso-1-naphthol-4-sulfonic acid (nitroso-S)-tetradecyldimethylbenzylammonium (TDBA) naphthalene as an adsorbent using a simple funnel tipped glass tube. Manganese reacts with nitroso-S to form a water soluble brown colored chelate anion. The chelate anion forms a water insoluble Mn-Nitroso-S-TDBA ion pair on naphthalene packed in a column in the pH range 9.6-10.5 at a flow rate of 1-2 ml/min. The solid mass consisting of manganese complex and naphthalene is dissolved in 5 ml of dimethylformamide (DMF) and the metal determined by second derivative spectrophotometry. The calibration curve is linear in the concentration range 0.25-35.0 micrograms of Mn in 5 ml of the final DMF solution. Eight replicate determinations of 25 micrograms of standard manganese solution give a mean peak height of 4.0 with a correlation coefficient of 0.9995 and relative standard deviation of +/- 1.1%. The sensitivity was calculated to be 0.502(d2 A/d lambda 2)/microgram ml-1 from the slope of the calibration curve. The detection limit was 0.020 microgram ml-1 for manganese at the minimum instrumental settings (signal to noise ratio = 2). Various parameters effecting the method such as the effect of pH, volume of aqueous phase and interference of a number of metal ions on the determination of manganese have been evaluated to optimize the conditions for its determination in standard alloys and biological samples.     

Differential pulse polarographic determination of tin in alloys and environmental samples after preconcentration with the ion pair of 2-nitroso-1-naphthol-4-sulfonic acid and tetradecyldimethylbenzylammonium chloride onto microcrystalline naphthalene or by column method

A highly selective, sensitive, rapid and economical differential pulse polarographic method has been developed for the determination of trace amount of tin in various standard alloys and environmental samples after adsorption of its 2-nitroso-1-naphthol-4-sulfonic acid-tetradecyldimethylbenzylammonium chloride on microcrystalline naphthalene in the pH range of 8.7-10.6. After filtration, the solid mass is shaken with 8-10 ml of 3.5 M hydrochloric acid and tin is determined by differential pulse polarography (DPP). Tin can alternatively be quantitatively adsorbed on 2-nitroso-1-naphthol-4-sulfonic acid-tetradecyldimethylbenzylammonium-naphthalene adsorbent packed in a column and determined similarly. The detection limit is 0.15 mug ml(-1) (signal to noise ratio=2) and the linearity is maintained in the concentration range 0.5-220 mug ml(-1) with a correlation coefficient of 0.9995 and relative standard deviation of +/-0.88%. Characterization of the electroactive process included an examination of the degree of reversibility. Various parameters such as the effect of pH, volume of aqueous phase and interference of a number of metal ions on the determination of tin has been studied in detail to optimize the conditions for determination in standard alloys and environmental samples.