Extraction-spectrophotometric determination of vanadium with N-m-tolyl-N-phenylhydroxylamine and its application to coal and coal fly-ash

N-m-Tolyl-N-phenylhydroxylamine is proposed for the spectrophotometric determination of small amounts of vanadium. The reddish-violet complex formed with the reagent in 3-6M hydrochloric acid after extraction with chloroform shows an absorption maximum at 530 nm, and obeys Beer's law for 0-76.5 mug of vanadium in 10 ml of chloroform. The proposed method has been successfully applied to the determination of vanadium in coal and coal fly-ash.     

Extraction-spectrophotometric determination of vanadium with 5,5′-dithiodisalicylhydroxamic acid (DTDSHA)

A new method for the extraction-spectrophotometric determination of V(V) is proposed. The violet complex V(V)-5,5′-dithiodisalicylhydroxamic acid formed in aqueous medium (pH 5.0) is extracted into a solution of trioctylmethylammonium chloride (Adogen 464) in toluene, and its spectrophotometric characteristics are studied. The stoichiometry of the complexes formed is 1:1 and 2:1 (reagent:vanadium), and 1:3 for the ionic association complex (2:1):trioctylmethylammonium ion. The system follows Beer's law at pH 5.0 (λ = 550 nm) over the concentration range 0.4 to 2.0 ppm (ε = 7.34 × 10³ liter · mol⁻¹ · cm⁻¹). The method is applied for the determination of vanadium in steel.     

Extraction-spectrophotometric determination of chromium with Nitrotetrazolium Blue

The interaction of Cr(VI) and Nitrotetrazolium Blue has been examined. A 12 NTB (CrO₃Cl)₂ ion-associate is formed and is extractable into 1,2-dichloroethane. The optimum conditions have been established. The molar absorptivity at 260 nm was (8.2 ± 0.06) × 10⁴L mol^–1cm^–1. Beer's law was obeyed in the range 0.01–0.4 g ml^–1 Cr(VI). A sensitive and selective method for determination of micro-quantities of Cr(VI) in soils and steels is suggested.     

Extraction-spectrophotometric determination of iron with 1,2,4,6-tetraphenylpyridinium perchlorate

Summary In 7M hydrochloric acid medium, iron(III) forms an ion-association compound with 1,2,4,6-tetraphenylpyridinium perchlorate (TPPP) which is extractable into isoamyl acetate. The extracted ionpair, which has an Fe: TPPP mole ratio of 11, is used for the spectrophotometric determination of iron (=3.10×10⁴l·mole^–1· cm^–1) in the concentration range 0.1–1.5g/ml in the organic phase. The interference of a number of foreign ions has been investigated. The method is applicable to the determination of iron in various materials.     

Extraction-spectrophotometric determination of hydrogen sulphide

A sensitive spectrophotometric method for the determination of trace amounts of hydrogen sulphide (H2S) after fixing in a modified zinc acetate-disodium ethylenediaminetetraacetate-sodium hydroxide solution is described. The fixed H2S is stable for 3 d. The reaction of iodate with H2S in the presence of acid and an excess of chloride leads to the formation of ICI which is stabilised as ICI2-. The species formed reacts with 2',7'-dichlorofluorescein to form 2',7'-dichloro-4',5'-diiodofluorescein which is extracted into a mixture of 15% isoamyl acetate in isoamyl alcohol. The colour system obeys Beer's law in the range 0-2.5 micrograms of H2S. The coefficient of variation is 4.5% for ten determinations of 2.0 micrograms of H2S. The effect of interfering gases on the determination is discussed. The method was applied to the determination of residual amounts of H2S present in a laboratory fume cupboard and the results obtained were compared with those given by the widely used Methylene Blue method. The method can be used to determine down to 0.3 micrograms of H2S.     

Extraction-spectrophotometric determination of tungsten with thiocyanate and some amidines

The procedure is based on reduction of W(VI) to W(V) by tin(II) chloride in 6 M hydrochloric acid, and extraction of the resultant thiocyanate complexes with a benzene solution of amidine. The complex coagulates and is dissolved in the benzene by addition of 1-pentanol. The maximum molar absorptivities of the complexes with 8 amidines in benzene/1-pentanol (9:1, v/v) are in the range 12 100–18 400 mol^?1 cm^?1. The simplest compound, N,N-diphenylbenzamidine gives the best sensitivity; the linear range covers 5–90 μg W in 10 ml of final solution; the detection limit is 2 ng W ml^?1. The method is applied to alloy steels.     

Extraction-spectrophotometric determination of mercury with 1,2,4,6-tetraphenylpyridinium perchlorate

The characteristics of 1,2,4,6-tetraphenylpyridinium perchlorate (TPPP) as a reagent for the formation of ion-pair complexes with metal-bromide anions, and its application to the spectrophotometric determination of mercury are described. This reagent forms a 1:1 complex with bromomercurate(II) ions that is slightly soluble in water and can be extracted with isopentyl acetate. The optimum conditions are about 0.5 M sulphuric acid and 0.03 M potassium bromide. Mercury can be determined at 310 nm in the range 0.04–0.5 μg ml^?1; the apparent molar absorptivity is 2.63 × 10⁴ l mol^?1 cm^?1, and the conditional stability constant is log K - 4.7 ± 0.1 at 20°C. The main interferences are easily removed. Mercury can be determined in sphalerites and zinc amalgams.     

Extraction-spectrophotometric determination of uranium/VI/ with tropolone

Tropolone reacts with uranium/VI/ and forms orange yellow precipitate extractable in chloroform. The maximum absorption occurs at 405 nm and the absorbance is found to remain constant in the pH range of 5.5 to 7.0. Beer's law is obeyed upto 37.6 ppm of U/VI/. The sensitivity of the colour reaction is 0.034 g cm^–2. Most of the common ions do not interfere. The method becomes more selective by masking some of the interfering cations with EDTA. The method was applied to determine uranium in monazite sand.This work is a part of the Ph.D. Thesis.     

Extraction-spectrophotometric determination of anionic surfactants with a flow-injection system

Anionic surfactants are preconcentrated from 5-ml samples by extraction as the ion-pair with ethyl violet into toluene. The absorbance of aliquots of the toluene phase is measured at 610 nm in a flow-injection system. A phase converter is located prior to the injection valve to convert a water stream to, pumped with ordinary pump tubing, to a toluene stream. The working range was 0.01–1.0 mg l^?1 and the reproductibility (r.s.d, n = 10) was 2% for 0.4 mg l^?1 sodium dodecyl sulphate. The non-aqueous flow-injection system serves to miniaturize the extraction from separatory funnel (200 ml) to test tube (10 ml) scale without loss of precision or validity.     

Extraction-spectrophotometric determination of palladium with triphenylphosphine (TPP)

Palladium is extracted with triphenylphosphine (TPP) solution in benzene from hydrochloric acid medium as the PdCl₂ · 2TPP complex showing maximum absorption at 346 nm and a molar absorptivity of ? = 2.26 × 10⁴.The conditions of palladium extraction have been examined and the composition of the extracted species has been found to be PdCl₂ · 2TPP.A 20-fold excess of other platinum and transition metals has no effect on the palladium extraction. Palladium can be determined at platinum concentrations up to 5 mg/ml provided that the result is corrected for the blank. The elaborated method has been applied to the analysis of platinum samples containing not less than 10^?3% of palladium.     

Extraction-spectrophotometric determination of uranium(VI) with PAR and N-octylacetamide

A new and simple method for selective spectrophotometric determination of uranium(VI) with 4-(2-pyridylazo)resorcinol (PAR) and N-octylacetamide into benzene over pH 7.0–9.0 is described. The molar absorptivity of the complex with 9 different amides is in the range of (0.40–3.2)·10⁴ 1·mol^–1·cm^–1 at the absorption maximum. Out of these, the most sensitive compound N-octylacetamide (OAA) was chosen for detailed studies in the present investigation. The detection limit of the method is 0.008 g U·ml^–1. The system obeys Beer's law in the range of 0–5 g U·ml^–1. The method is free from interferences of most of the common metal ions except vanadium(V) and copper(II), which are masked by proper masking agents. The composition of the complex is determined by curve-fitting method. The method has been applied for the recovery of the metal from rock samples and synthetic mixtures.     

Separation of rhenium by extraction with crown ethers and flow-injection extraction—spectrophotometric determination with Brilliant Green

The extraction behavior of perrhenate with crown ethers was studied and methods for the separation and determination of rhenium were developed. The distribution ratio of perrhenate with dicyclohexano-18-crown-6 (DC18C6) increases with increases in the dielectric constant of organic solvents and in the potassium ion concentration of aqueous solution. The molar ratios of crown ether to KReO₄ in the extracted species are probably 1:1 for DC18C6, dibenzo-18-crown-6 and 18-crown-6 and 2:1 for benzo-15-crown-5 and 15-crown-5. Microgram amounts of rhenium were satisfactorily separated from large amounts of molbdenum(VI) by extraction with DC18C6 in 1,2-dichloroethane from 2 M potassium hydroxide solution containing tartrate and by back-extraction with sodium phosphate buffer solution after the addition of a twofold volume of hexane to the organic phase. Rhenium was determined by the flow-injection extraction-photometric method with Brilliant Green. Rhenium was satisfactory determined in molybdenite and other ore samples.     

Extraction-spectrophotometric determination of niobium with dibenzo-18-crown-6 and thiocyanate

A method is described for the direct spectrophotometric determination of micro-amounts of niobium by extraction into a benzene solution of dibenzo-18-crown-6 (L) from 3M hydrochloric acid containing potassium thiocyanate. The molar absorptivity of the extracted complex is 3.85 +/- 0.03 x 10(4) 1.mole(-1).cm(-1) (relative standard deviation 0.8%). Co-ordinatively unsaturated complexes of the type [NbO(SCN)(3)](2)L and NbO(SCN)(3)L are extracted, along with ion-pairs, especially when small amounts of L are used for extraction. The ion-pair complex [NbOCl(2)(SCN)(3)][(LK)(2)] seems to be the main species formed in the organic phase.     

Extraction-spectrophotometric determination of cadmium with pyruvylidine-2-hydrazinobenzothiazole in benzene

The proposed method is suitable for the determination of 0—60 μg of cadmium in a 5-ml sample, with good reproducibility and excellent selectivity.     

Extraction-spectrophotometric determination of some antihistaminic agents with fast green FCF

A rapid, simple, precise, accurate and highly sensitive method for the determination of some antihistaminic agents such as dimethindene maleate (DMM), embramine hydrochloride (EMH), isothipendyl hydrochloride (IPH), mebhydrolin napadisylate (MHn), methdilazine hydrochloride (MDH), promethazine hydrochloride (PMH), trimeprazine tartrate (TMT) and triprolidine hydrochloride (TPH) in bulk samples and pharmaceutical preparations is proposed. The method is based on the formation of a chloroform-soluble ion-association complex between the antihistaminic agent and Fast Green FCF at pH 5.0 with an absorption maximum at 620 nm. The composition of antihistaminic agent and Fast Green FCF in each ion-association complex is studied. The relative standard deviation of the proposed method is less than 1.3%, the percent recovery is 99.4–100.2% and the results are not significantly different from the standard methods at the 95% confidence level.