Dialkyltin salts as extractants in methods for the determination of arsenic and phosphorus

Dialkyltin salts are suitable as extractants for various oxygen-containing anions. They are particulary powerful for the extraction of arsenate and phosphate ions, but are also useful for liquid-liquid extraction of anions of dibasic acids. It is shown that the high extraction power of these dialkyltin complexes can be explained by formation of innersphere complexes with the extracted anions. A method is proposed for the separation of arsenic, phosphorus and silicon using dialkyltin salts. Applications to the extraction-spectrophotometric determination of phosphorus and arsenic in vanadium and steel, and to extraction/atomic absorption determinations of arsenic and phosphorus in metals and alloys are surveyed. The use of the dialkyltin salts for the neutron activation determination of arsenic and as active components in membranes of ion-selective electrodes for phosphorus(V) and arsenic(V) is demonstrated.     

Determination of phosphorus in semiconductor grade silicon by neutron activation analysis

A method of determination of phosphorus in silicon has been elaborated. The separation of phosphorus is based on the extraction of phosphomolybdic complex in the presence of hold-back carriers of Ta and Au. Contamination factors for various impurities were determined. The lower limit of determination equals 3·10^?11 g P. Types of errors in the determination of concentration profiles are discussed.     

Spectrophotometric determination of traces of phosphorus by an extraction method

A general method is presented for the spectrophotometric determination of phosphorus at trace levels. It involves extraction of the yellow molybdophosphoric acid with isobutyl acetate and subsequent reduction to heteropoly blue. The method covers the range 0.2–20 μg of phosphorus. A comprehensive study of interferences using standard additions of 10 and 20 μg of phosphorus was carried out and modifications are described to permit the determination of phosphorus in a wide variety of metals and salts.     

New procedure for the examination of the degradation of volatile organonitrogen compounds during the treatment of industrial effluents

We present a new procedure for the determination of 32 volatile organonitrogen compounds in samples of industrial effluents with a complex matrix. The procedure, based on dispersive liquid–liquid microextraction followed by gas chromatography with nitrogen‐phosphorus and mass spectrometric detection, was optimized and validated. Optimization of the extraction included the type of extraction and disperser solvent, disperser solvent volume, pH, salting out effect, extraction, and centrifugation time. The procedure based on nitrogen‐phosphorus detection was found to be superior, having lower limits of detection (0.0067–2.29 μg/mL) and quantitation as well as a wider linear range. The developed procedure was applied to the determination of content of volatile organonitrogen compounds in samples of raw effluents from the production of bitumens in which 13 compounds were identified at concentrations ranging from 0.15 to 10.86 μg/mL and in samples of effluents treated by various chemical methods.     

Substoichiometric extraction of phosphorus

A study of the substoichiometric extraction of phosphorus is described. Phosphorus was extracted in the form of ternary compounds such as ammonium phosphomolybdate, 8-hydroxyquinolinium phosphomolybdate, tetraphenylarsonium phosphomolybdate and tri-n-octylamine phosphomolybdate. Consequently, phosphorus was extracted substoichiometrically by the addition of a substoichiometric amount of molybdenum for all four phosphomolybdate compounds. On the other hand, phosphorus could be separated substoichiometrically with a substoichiometric amount of tetraphenylarsonium chloride or tri-n-octylamine. Stoichiometric ratios of these ternary compounds obtained substoichiometrically were 1∶12∶3 for phosphorus, molybdenum and organic reagent. Applicability of these compounds to phosphorus determination was also discussed.     

Simultaneous determination of phosphorus. arsenic and germanium and the separation of silicon and arsenic by solvent extraction

A simple, rapid, accurate and reliable method for the simultaneous determination of phosphorus, arsenic and germanium as their heteropoly blue complexes is reported. The method involves selective extraction of phosphomolybdic acid at pH 1.0-0.8, and selective extraction of germanomolybdic acid by isooctyl alcohol at pH 0.4, followed by back-extraction of the germanomolybdic acid with water, and reduction of arsenomolybdic acid in the remaining aqueous phase. A rapid and reliable method is also reported for the simultaneous determination of arsenic and silicon by selective extraction of silicomolybdic acid with isooctyl alcohol at pH < 0.4 and the back-extraction of the silicomolybdic acid with water; arsenic is determined in the remaining aqueous phase. The procedure can be applied to the simultaneous determination of phosphorus, arsenic and silicon.     

Directly suspended droplet microextraction in combination with microvolume UV-vis spectrophotometry for determination of phosphate

A miniaturized methodology for the determination of phosphate in waters has been developed by combining directly suspended droplet microextraction (DSDME) with microvolume spectrophotometry. The method is based on the extraction of the ion pair formed between 12-molybdophosphate and malachite green onto a microdrop of methyl isobutyl ketone and subsequent spectrophotometric determination with no dilution. An enrichment factor of 325 was obtained after 7.5 min of microextraction. The detection limit was 6.1 nM phosphate and the repeatability, expressed as relative standard deviation, was 2.7% (n = 6). The method was successfully applied to the determination of dissolved reactive phosphorus in different freshwater samples.     

Application of modified counter-current technique to the determination of tungsten in molybdenum

More than trace amounts of molybdenum interfere in the determination of tungsten by the dithiol method. A simplified counter-current extraction method is described which allows the determination of 5 p.p.m. or more of tungsten in a molybdenum matrix. The optimum conditions for the separation were a 6 M HCL-2.4 M HF medium and methyl isobutyl ketone as extractant; the percentage extractions in a single pass were 85% and 15% for molybdenum and tungsten, respectively.     

Comparison of Methods for the Preparation of Sewage Sludge Samples Prior to the Spectrophotometric Determination of Phosphorus

Abstract

Three procedures for the preparation of sewage sludge samples prior to the colorimetric determination of phosphorus as “molybdenum blue” were evaluated. Using samples of the US EPA's municipal digested sludge as a reference material, sulfuric acid/ammonium persulfate digestion, muffle furnace ignition followed by extraction of the ash with hydrochloric acid, and direct extraction of the sewage sludge with sodium bicarbonate solution were compared in terms of phosphorus recovery as determined by colorimetric measurements. On the basisof phosphorus recovery, the samples prepared by muffle furnace ignition/hydrochloric acid extraction of the ash showed the best accuracy and precision. This procedure was also superior in terms of the time and effort expended in the preparation of the sewage sludge samples.     

A chemical amplification method for the sequential estimation of phosphorus, arsenic and silicon at ng/ml levels by d.c. polarography

A method is described for the sequential determination of phosphorus, arsenic and silicon at ng/ml levels by d.c. polarography. These elements are converted into their heteropolymolybdates and separated by selective solvent extraction. Determination of the molybdenum in the extract gives an enhancement factor of 12 for determination of the hetero-atom. A further enhancement by a factor of 40 is achieved by determining the molybdenum by catalytic polarography in nitrate medium. Charging-current compensation is employed to improve precision and the detection limit. The detection limits for phosphorus, arsenic and silicon are 0.5, 4.7 and 3.1 mu/gl., respectively and the relative standard deviation is 2-2.5%.     

Ionic liquid-salt aqueous two-phase extraction based on salting-out coupled with high-performance liquid chromatography for the determination of sulfonamides in water and food

Ionic liquid-salt aqueous two-phase extraction coupled with high-performance liquid chromatography with ultraviolet detection was developed for the determination of sulfonamides in water and food samples. In the procedure, the analytes were extracted from the aqueous samples into the ionic liquid top phase in one step. Three sulfonamides, sulfamerazine, sulfamethoxazole, and sulfamethizole were selected here as model compounds for developing and evaluating the method. The effects of various experimental parameters in extraction step were studied using two optimization methods, one variable at a time and Box–Behnken design. The results showed that the amount of sulfonamides did not have effect on the extraction efficiency. Therefore, a three-level Box–Behnken experimental design with three factors, which combined the response surface modeling, was used to optimize sulfonamides extraction. Under the most favorable extraction parameters, the detection limits (S/N?=?3) and quantification limits (S/N?=?10) of the proposed method for the target compounds were achieved within the range of 0.15–0.3 ng/mL and 0.5–1.0 ng/mL from spiked samples, respectively, which are lower than or comparable with other reported approaches applied to the determination of the same compounds. Finally, the proposed method was successfully applied to the determination of sulfonamide compounds in different water and food samples and satisfactory recoveries of spiked target compounds in real samples were obtained.     

Prochlorperazine bismethanesulfonate as a new reagent for the spectrophotometric determination of palladium

A simple, rapid, and selective method for the determination of palladium is described. The orange-red palladium(II)-prochlorperazine bismethanesulfonate complex in the presence of hydrochloric acid-sodium acetate buffer exhibits maximum absorbance at 480 nm with a molar absorptivity of 4.32 × 10³ liters mol^?1 cm^?1. The sensitivity of the reaction is 24.62 ng cm^?2. The system obeys Beer's law over the concentration range 0.4–20 ppm of palladium with an optimum concentration range of 1–19 ppm. The apparent stability constant of the complex is found to be log K = 5.3 ± 0.1 at 27 °C. The effects of pH, time, temperature, order of addition of reactants, reagent concentration, and interferences from various ions are reported. The proposed method offers the opportunity to carry out the determination at room temperature without the need for an extraction step. The method is also found to be suitable for the determination of palladium in jewelry alloy.     

Bisxantphos: Stereoselective synthesis and coordination behaviour of a new class of cyclic double bridged diphosphines

A new class of cyclic double bridged diphosphine ligands was developed and the coordination properties are described. The reaction of 4,5-dilithioxanthene with dichlorophenylphosphine gave a cyclic double bridged diphosphine ligand based on two xanthene backbones (4) as a single stereoisomer. X-ray crystal structure determination revealed that the groups bridging the two phosphorus atoms are arranged in a syn-disposition. This new cyclic bisxantphos structure was modified with bulky residues at the third substituent of the phosphorus atoms, thus forming cavity-shaped ligands.     

Colorimetric determination of palladium with pyridine-2-aldehyde-2'-pyridylhydrazone

The colorimetric determination of palladium described involves the extraction of chloro(PAP)palladium(II) from an acidic aqueous solution into o-dichlorobenzene and measurement of the absorbance of the extract solution. The method is suitable for the determination of 10–100 μg of palladium. Tolerance amounts for many metals have been determined and compare very favourably with those of other methods.     

Anodic stripping voltammetry of tellurium(IV) in aqueous solution and mixed solvents

The anodic stripping determination of Te(IV) using a rotating glassy carbon disc electrode is described. 0.1 ppm tellurium can be determined in 1 M HCl. Interfering effects of the metals forming intermetallic compounds with tellurium on the electrode are eliminated by solvent extraction. Te(IV) is determined either after its extraction — as an ion associate or as the chelate with diphenylthiocarbazone — in the organic phase which is adjusted for the stripping determination by the addition of methanolic solution of LiCl or after the separation of all interfering elements by an extraction procedure involving the extraction of Te(IV) into methylisobutylketone and back extraction of Te(IV) with water followed by the separation of the remaining interfering elements into diisopropylether. The proposed method enables the determination of 10 μg Te in the presence of 25 mg Pb and Sb and 0.5 mg Ag, Cu, Bi, As, Sn, Cd, Zn with reproducible results and error ±5%.     

Spectrophotometric determination of palladium after extraction of the chloro-stannous complex by tri-n-octylamine

The complex formed between palladium(II) and tin(II) in hydrochloric acid solutions, and its extractability by tri-n-octylamine were investigated. Two different species were obtained: one a brown-red complex and the other yellow. Both were extracted into tri-n-octylamine in benzene, but the yellow species which had a definite absorption maximum at 410 mμ was more suitable for the determination of palladium. A method is described for the spectrophotometric determination of palladium in the presence of many other elements. Both species are considered to be anionic and a mechanism for their extraction is proposed.     

Photometric determination of traces of antimony with rhodamine b after sulfide precipitation

A method is described for the colorimetric determination of as little as a few tenths of a part per million of antimony in samples composed primarily of elements of atomic numbers 1–28 (e.g., geo materials).Antimony is isolated by sulfide precipitation in mineral acid medium after reduction of ferric iron with hydroxylamine hydrochloride, with final determination by rhodamine B-benzene extraction. The procedure provides for the presence of gallium, thallium, tungsten and gold.     

Determination of sodium and phosphorus in organophosphorus compounds by fast-neutron activation

A method is described for the determination of sodium and phosphorus using the NG-160 neutron generator and an automated pneumatic transport device. The reactions²³Na (n, p)²³Ne and³¹P(n, α)²⁸ Al are utilized for the determination of sodium and phosphorus, respectively. For the determination of sodium, hermetically sealed vials are indispensable. The time required for one determination is 6 to 8 min. A rapid method for the determination of macro-amounts of sodium against a phosphorus background is also described, leading to the general conclusion that isotopes with γ-quantum energies close to 0.51 MeV can be determined against a background of positron radiation sources in a well-type crystal.     

Factorial design for multivariate optimization of preconcentration system for spectrophotometric phosphorus determination

The present paper proposes a preconcentration procedure for phosphorus determination by using ultraviolet-visible spectrophotometer. It is based on the formation of phosphomolybdate and its reduction to molybdenum blue. Phosphorus extraction as phosphomolybdenum blue complex was performed onto Amberlite XAD-4. The optimization step was carried out using two-level full factorial design. Three variables (resin amount, sample volume, flow rate) were regarded as factors in the optimization. The relative standard deviation was 2% at 0.08 μg mL⁻¹. The limit of detection was found to be 2.23 μg L⁻¹ (N = 15). The proposed solid-phase extraction procedure was applied to phosphorus in some fruit leaves, natural waters, and a standard reference material (SRM 1515 apple leaves).     

Properties and analytical applications of the heteropolymolybdates of phosphorus, arsenic, silicon and germanium-IV Determination of phosphomolybdic and silicomolybdic acids via the molybdenum content, with phenylfluorone

Procedures are proposed for the determination of phosphorus and silicon in the ppM range, by extraction of phosphomolybdic and silicomolybdic acids with organic solvent, decomposition of the complex and spectrophotometric determination of its molybdenum content.