Analytical separation of antimony(III) from bismuth(III), lead(II), gallium(III), thallium(III), tellurium(IV) and tin(IV) with cyanex 302

A method is proposed for the separation of antimony(III) (100–400 g) from bismuth(III), lead(II), gallium(III), thallium(III), tellurium(IV) and tin(IV) from an aqueous solution of pH 0.5–1.5 using 8×10^–3–1×10^–2 mol dm^–3 cyanex 302 dissolved in toluene as an extractant. The antimony is stripped from the cyanex phase with water and determined spectrophotometrically with iodide. Various experimental parameters are optimized and the probable 13 stoichiometry of the extracted species is evaluated. The method is applicable to the analysis of alloys and pharmaceutical samples. The separation and determination take only 20 min.     

Determination of ascorbic acid in asparagus by differential pulse polarography

A useful method for the determination of ascorbic acid in a vegetable product (asparagus) by differential pulse polarography has been set up and evaluated. Extraction and instrumental conditions were optimized. The analytical parameters are: linearity (0–18.18 g/ml); detection limit (0.182 g/ml); instrumental and method precision (2.77% and 4%, respectively); accuracy (96.9–113.4%). These data show that the method is sufficiently sensitive, reliable and accurate. It was also compared with the official fluorometric AOAC method.     

Determination of lutetium by fluorimetry, using BPMPHD and CTMAB

Lutetium(III) forms an association compound with a new synthetic reagent, 1,6-bi(1-phenyl-3-methyl-5-pyrazolone-4)hexandione (BPMPHD), and cetyltrimethylammonium bromide (CTMAB). The compound enhances the natural fluorescence of BPMPHD remarkably, upon which a new fluorescence method was developed for determining lutetium in rare earth (RE) samples. The determination range was 1.80 × 10^–7–8.8 × 10^–6 g/ml. The determination limit was 29 ng/ml. The composition of the ion associate was [Lu(BPMPHD)₂]–CTMAB⁺.     

Determination of trace scandium by ion-exchanger phase spectrophotometry withp-nitrochlorophosphonazo

Ion-exchanger phase Spectrophotometry withp-nitrochlorophosphonazo (CPApN) has been developed for the determination of scandium. The linear range is 1–8 g of scandium in 50 ml of solution, using 0.8 g of resin, with an apparent molar absorptivity of 2.76 × 10⁵ 1 mol^–1 cm^–1. Aluminum and rare earth elements in reasonable amounts do not interfere. The method has been applied successfully to the determination of scandium in alloys, with relative standard deviations of 2–4%.     

Determination of unsulphonated quinoline yellow in soft drinks by solid-phase spectrophotometry

A spectrophotometric method for determination of quinoline yellow spirit soluble (QYSS) in the presence of sulphonated quinoline yellow water soluble (QYWS) in soft drinks at trace levels is reported. The method is based on the fixation of QYSS on C-18 silica gel, followed by measurement of its absorbance at = 418 nm in the solid phase after being packed in a 1-mm cell. The applicable concentration range was 1.5–15.0 ng/ml, the detection limit 0.4ng/ml and the relative standard deviation 5.2%. The method was applied satisfactorily to the determination of this compound in samples of commercial soft drinks.     

Determination of Squalene Using High-Performance Liquid Chromatography with Diode Array Detection

A high-performance liquid chromatographic method with photodiode array detection has been developed for the determination of squalene. After treated by extraction and fractional crystallization, squalene was analyzed on a C₁₈ column (150 × 3.9 mm, 5 m) with acetonitrile as mobile phase. Excellent linearity of the calibration curve was observed in the range of 100–40000 gL^–1 and the detection limit was 40 gL^–1. The recoveries were from 89.6% to 100.5% and the relative standard deviations were from 0.5% to 1.4%. The method was successfully applied to the determination of squalene in squalene capsules, olive oil, algal lipids and algal cells.     

Determination of the Enantiomers of Tamsulosin Hydrochloride and its Synthetic Intermediates by Chiral Liquid Chromatography

A chiral liquid chromatographic method is described for the determination of the enantiomers of tamsulosin hydrochloride and its synthetic intermediates. Enantioseparation was achieved on a Chiralcel OD-R column (250 mm × 4.6 mm, 10 m) using a mobile phase consisting of a mixture of 0.5 mol L^–1 sodium perchlorate and acetonitrile (80:20, v/v, pH 4.0). The flow rate was 0.4 mL min^–1 and detection was at 223 nm. Excellent enantiomer separations were achieved for tamsulosin hydrochloride and its synthetic intermediates. No other methods are available for the separation of these enantiomers. The method developed in this study has been successfully applied for purity control.     

Analysis of chromates for traces of Cr(III) by solvent extraction and inductively coupled plasma atomic emission spectrometry

Summary A method for the determination of quantities of 0.5–500 g of Cr(III) in the presence of chromates and dichromates is described. The samples are dissolved in an aqueous solution buffered at pH 7.0; the Cr(III) is selectively chelated with 2-thenoyltrifluoroacetone and extracted into xylene. The extracted chromium is analyzed using inductively coupled plasma emission spectrometry. Extraction of 1.0 g Cr(III) from 5.0 mg K₂Cr₂O₇ was accomplished and easily determined in a volume of 25 ml of xylene. The relative standard deviation for the determination of Cr(III) contents ranging from 4.0 × 10^–8 g/ml to 2.0 × 10^–8 g/ml was ± 0.079. Using a minimum signal to noise ratio of 101, the detection limits of the method were determined to be approximately 2.0 × 10^–8 g/ml xylene. Chloride, high surface area silica, and easily oxidized amorphous boron give rise to only minor interferences.

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Analyse von Cr(III)-Spuren in Chromaten durch Extraktion und ICP-Atomemissionsspektrometrie

Zusammenfassung Ein Verfahren wird beschrieben zur Bestimmung von 0,5–500 g Cr(III) in Gegenwart von Chromaten und Dichromaten. Die Proben werden in Pufferlösung pH 7,0 gelöst, und 2-Thenoyltrifluoraceton behandelt und Cr(III) selektiv mit Xylol extrahiert. Die Bestimmung erfolgt durch ICP-Spektrometrie. 1,0 g Cr(III) konnte von 5,0 mg K₂Cr₂O₇ getrennt und in einen Volumen von 25 ml Xylol bestimmt werden. Die relative Standardabweichung im Bereich von 4,0 · 10^–8 bis 2,0 · 10^–7 g Cr(III)/ml betrug ± 0,079. Bei einem Verhältnis SignalUntergrund = 101 wurden Nachweisgrenzen um 2,0 · 10^–8 g/ml gefunden. Störungen durch Chlorid, Siliciumdioxid und amorphes Bor sind gering.

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This work was supported by the U.S. Department of Energy (DOE) under contract number DE-AC04-76-DP00789

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A U.S. DOE facility     

Spectrophotometric determination of iron in aluminium metal and some non-ferrous alloys

A new, sensitive and selective spectrophotometric method is suggested for the determination of traces of iron(III) based on complex formation with hematoxylin in presence of cetyltrimethylammonium bromide (CTAB). Addition of CTAB shifted the absorption maximum of the iron-hematoxylin complex from 630 to 640 nm and increased its molar absorptivity from 9.88 × 10⁴ to 1.16 × 10⁵ 1·mol^–1·cm^–1. The method adhered to Beer's law up to 0.4 and 0.2 g/ml of iron in presence and absence of CTAB, respectively. The corresponding values of Sandell's sensitivity were 0.5 and 0.6 ng·cm^–2. The effect of reagent and surfactant concentrations, pH and standing time were investigated. EDTA, tartrate and sodium fluoride were used as masking agents for most of the interfering ions. The method was successfully used for the determination of iron in aluminium metal and some non-ferrous alloys.     

Dispersity and kinetic characteristics of dissociation of mono- and hemiaquo adducts of copper N,N′-ethylenebis(acetylacetoniminate) under nonisothermal conditions

Using optical microscopy and thermogravimetry, we have established that determination of the kinetic characteristics of dissociation for the monoaquo adduct of copper N,N-ethylene-bis(acetylacetoniminate) with particle size 0.5–2 mm is hindered by self-dispersal processes. Using a piezoquartz microbalance, we have obtained the kinetic parameters for thermolysis for a phase whose crystal sizes are substantially smaller than the minimal size after self-dispersal of a block of a large crystal (0.5–2 m). For thermolysis of the hemiaquo adduct not accompanied by self-dispersal, the kinetic characteristics of the process for phases of dispersity 0.5–2 mm and 0.5–2 m are comparable.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 28, No. 3, pp. 226–231, May–June, 1992.     

Determination of 6-amino-2,2-dimethyl-1,3-dioxepan-5-ol by postcolumn derivatization witho-phthalaldehyde/2-mercapto-ethanol after ion-pair chromatography

Summary A high-performance liquid chromatographic method is discribed for the determination of 6-amino-2,2-dimethyl-1,3-dioxepan-5-ol using Spherisorb ODS II stationary phase and mobile phase 30:70 (v/v) methanol: aqueous 1-octane sulfonic acid. Detection was fluorimetric following postcolumn derivatization with o-phthaladehyde/2-mercaptoethanol. The procedure was applied to the analysis of aqueous solutions and microcrystalline suspensions in liquid paraffin, prepared for investigation of the toxicological profile. The method was validated for selectivity, linearity of detector response, repeatability, limit of detection and quantitation. The HPLC method was selective. The instrumental limit of detection was 0.5 ng per injection (0.05 g mL^–1). The method detection limits were 0.5 g mL^–1 aqueous solution and 5 g mL^–1 liquid paraffin suspension, the quantitation limit 0.05 mg mL^–1 aqueous solution and 1.0 mg mL^–1 liquid paraffin. Linearity was within 0.94–47.1 g mL^–1. Intra-assay accuracy accounted for 99–100% in the range 0.05–226 mg mL^–1 aqueous solution, intra-assay precision for 2% (C.V.). For microcrystalline liquid paraffin suspensions with 1 and 250 mg mL^–1 99 and 109% was found for intra-assay accuracy. Intra-assay precision was 5% (C.V.). Reliable results over a wide concentration range can be obtained. The procedure is considered valid for determination of the analyte in aqueous solution or microcrystalline paraffin oil suspensions.     

Polarographische Bestimmung kleiner Wolframmengen

Zusammenfassung Sehr kleine Wolframkonzentrationen von etwa 0,1–20 g/ml werden am besten in Grundlösungen mit 9–10 m PerchlorsÄure + 0,6–0,7 m WeinsÄure polarographisch bestimmt. Für höhere Konzentrationen von etwa 20–100 g/ml sind Lösungen mit 9–10 m SalzsÄure + 0,3 m WeinsÄure (oder 0,1 m CitronensÄure) + 0,01% Gelatine vorzuziehen.

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Summary For the determination of very small concentrations of tungsten (0.1 to 20 g/ml) solutions with 9–10 M perchloric + 0.6–0.7 M tartaric acid are especially suitable. The determination of higher concentrations (20–100 g/ml) should be preferably performed in solutions with 9–10 M hydrochloric + 0.3 M tartaric acid (or 0.1 M citric acid) + 0.01% gelatin.

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Herrn Prof. Dr., Dr. h.c. Dr. h.c. Dr. h.c. Wilhelm Klemm zum 70. Geburtstag gewidmet.     

Extraction and spectrophotometric determination of titanium(iv) with 3-hydroxy-2-methyl-1-(4-tolyl)-4-pyridone

Titanium(IV) in sulphuric, perchloric and hydrochloric acid media reacts with 3-hydroxy-2-methyl-1-(4-tolyl)-4-pyridone (HY) to give a complex which is extractable into chloroform. The composition of the extractable complex depends on the acidity of the aqueous phase and on which mineral acid is used. The mixed titanium-perchlorate-HY complex which is formed in the presence of excess of perchlorate is the most suitable for the spectrophotometric determination of titanium. The molar absorptivity of the complex is 1.6×10⁴1·mole^–1·cm^–1 at 355 nm. The optimum titanium concentration range is 0.5–6,g/ml. The method has been successfully applied to the determination of titanium in samples of bauxite and alumina refractory.     

High-Performance Liquid Chromatographic Method for the Determination of Nimesulide in Pharmaceutical Preparations

A simple, rapid, and precise high-performance liquid chromatographic method for the determination of nimesulide in pharmaceutical preparations was proposed using Ibuprofen as an internal standard. The separation was performed on a CLC C₁₈ (5 m, 25 cm × 4.6 mm i.d.) column with a mobile phase consisting of an acetonitrile–0.05 M KH₂PO₄ buffer mixture of pH 7.00 (55 : 45, v/v). The detection was carried out at 230 nm and the linearity range was found to be 0.5–100 g/mL. The method has been applied successfully to the determination of nimesulide in pharmaceutical formulations. The recovery values were found to be in the range of 99.23–100.13% with RSD values of less than 0.97%.     

Simultaneous determination of copper,mercury and lead by first-order derivative spectrophotometry using dithizone as reagent

A first-order derivative spectrophotometric method has been developed for the simultaneous determination of copper, mercury and lead at g/L levels using dithizone as reagent. The procedure involves the simultaneous extraction of these elements by dithizone in chloroform from weakly alkaline solutions. Linear calibration curves were obtained in the ranges 0.5–10 (Cu), 1–10 (Hg) and 1–10 (Pb) g present in 40 ml of aqueous phase with detection limits of 5 g/L (Cu) and 20 g/L (Hg and Pb). The R.S.D.s for 100 g/L of copper, mercury and lead were 2.5, 2.6 and 3.1% respectively, for 5 determinations. The method is applicable for the determination of copper and lead in marine sediment samples with good precision and accuracy.     

Voltammetric-enzymatic determination of ethanol in whole blood by flow injection analysis

Summary Two automatic methods are proposed for the voltammetric determination of ethanol in whole blood. They are based on the use of the enzymatic systems alcohol dehydrogenase/ nicotinamide adenine dinucleotide (method A) and alcohol dehydrogenase/nicotinamide adenine dinucleotide/ diaphorase/2,6-dichlorophenolindophenol (method B). The determination ranges are 2.5–30.0 g/ml and 0.5–30.0 g/ml with sampling rates of 60 and 30 samples/h, respectively. The coefficients of variation are about ±4%.

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Voltammetrisch-enzymatische Bestimmung von Ethanol in Vollblut durch Fließinjektionsanalyse

     

A New Spectrophotometric Method for the Determination of Cerium Using Leuco Disulphine Blue

A new, simple, highly sensitive spectrophotometric method for the determination of trace amounts of cerium(IV) is described. The method is based on the oxidation of leuco disulphine blue (LDSB) to its blue form of disulphine blue by Ce(IV) in a sulfuric acid medium (pH 1.3–3.0); the absorbance of the formed dye is measured in an acetate buffer medium (pH 3.0–4.8) at 635 nm. The color system obeys Beer's law in the concentration range from 0.5 to 5.5 g mL^–1 cerium with a molar absorptivity of 1.75 × 10⁴ L mol^–1 cm^–1 and a Sandell's sensitivity of 0.008 g cm^–2. All variables were studied in order to optimize the reaction conditions. The developed method has been successfully applied to the determination of cerium in high purity rare-earth oxides, soil, natural water, plant tissue, human hair, and rock samples.     

Column preconcentration of gold by adsorbing AuCl<Stack><Subscript>4</Subscript><Superscript>−</Superscript></Stack> onto methyltrioctyl ammonium chloride–naphthalene and subsequent atomic absorption spectrometric determination

A sensitive, selective and simple preconcentration method for ultra-trace gold determination has been developed that uses naphthalene–methyltrioctyl ammonium chloride (Aliquat 336s) as an adsorbent. Gold, in the form of AuCl₄^–, was retained by the adsorbent in the column at a flow rate of 1 ml min^–1. After filtration, the solid mass consisting of the gold complex and naphthalene was dissolved out of the column with 5 ml of N,N-dimethylformamide (DMF), and the metal was then determined by atomic absorption spectrometry. In the initial solution, the calibration graph of absorbance versus gold concentration was found to be linear in the range 0.5–150 ng ml^–1 Au(III) with r=0.997 (n =9), and the 3 s detection limit was 0.428 ng ml^–1. The relative standard deviation for eight replicate measurements of 20 g of gold was 2.14%. Preconcentration factors of 390 and 650 were achieved using 5 ml and 3 ml of DMF, respectively. The proposed method was successfully applied to the determination of gold in wastewater, processed pool water, slurry pool water, and raw well-water from the Moteh gold mine, and synthetic samples.     

Spectrophotometric determination of furosemide as its Fe(III) complex in pharmaceutical preparations

A new spectrophotometric method for determination of furosemide is described. The method is based on the reaction of furosemide with ferric chloride in pH range 5.2–6.2 and producing a red water-soluble (2 1) complex with maximum absorbance at 513 nm. By applying the methods of Sommer and Job involving non-equimolar solutions the conditional stability constant of the complex, at the optimum pH of 5.7, and ionic strength =0.1M, is found to be 10^6.5. Beer's law is obeyed up to 8 mmol/l furosemide concentration. The detection limit of the method is 0.03 mg/ml. The relative standard deviation (n=20) is 1.03% and relative error of the method is 0.5%. The proposed method was found to be suitable for the accurate and reproducible analysis of furosemide in tablets and ampoules, what is pointed by high recovery values 98.78–100.6% and low values of relative standard deviations 1.68–2.08%. The results obtained show that the method is applicable to routine analysis.     

Preconcentration technique for nonylphenol using cellulose cotton with homogenous liquid–liquid extraction for liquid chromatographic analysis

A powerful preconcentration method for nonylphenol (NP) has been developed for liquid-chromatography by combining the use of cellulose cotton (solid-phase extraction) with homogeneous liquid–liquid extraction. A 100 ml of sample solution was preconcentrated using cotton, and the eluate obtained (acetonitrile; 5 ml) was further preconcentrated to 50 l within 10 min using a homogeneous liquid–liquid extraction method (volume ratio, 2,000-fold; 100 ml 50 l). The sample concentration increases from preconcentration was 1,599-fold, and NP was extracted into the sedimented phase at 80%. The proposed method was applied to high performance liquid chromatography with fluorescence detection (FL/HPLC); the lowest determination limit obtained was 1.0×10^–9 mol l^–1.