Ion paired chromatography of iron (II,III), nickel (II) and copper (II) as their 4,7-Diphenyl-1,10-phenanthroline chelates

A reversed phase ion-paired chromatographic method that can be used to determine trace amounts of iron (II,III), nickel (II) and copper (II) was developed and applied to the determination of iron (II) and iron (III) levels in natural water. The separation of these metal ions as their 4,7-diphenyl-1,10-phenanthroline (bathophenanthroline) chelates on an Inertsil ODS column was investigated by using acetonitrile-water (80/20, v/v) containing 0.06 M perchloric acid as mobile phase and diode array spectrophotometric detection at 250-650 nm. Chromatographic parameters such as composition of mobile phase and concentration of perchloric acid in mobile phase were optimized. The calibration graphs of iron (II), nickel (II) and copper (II) ions were linear (r > 0.991) in the concentration range 0-0.5, 0-2.0 and 0-4.0 mug ml(-1), respectively. The detection limit of iron (II), nickel (II) and copper (II) were 2.67, 5.42 and 18.2 ng ml(-1) with relative standard deviation (n = 5) of 3.11, 5.81 and 7.16% at a concentration level of 10 ng ml(-1) for iron (II) and nickel (II) and 25 ng ml(-1) for copper (II), respectively. The proposed method was applied to the determination of iron(II) and iron(III) in tap water and sea water samples without any interference from other common metal ions.     

Reversed-phase high performance liquid chromatographic method for the determination of lansoprazole, omeprazole and pantoprazole sodium sesquihydrate in presence of their Acid-induced degradation products

A simple sensitive, selective and accurate reversed-phase high performance liquid chromatographic method was developed and validated for the quantitative determination of lansoprazole, omeprazole and pantoprazole sodium sesquishydrate in the presence of their acid-induced degradation products. The three compounds were monitored at 280 nm using Nova-Pak C(18) column and a mobile phase consisting of 0.05 M potassium dihydrogen phosphate : methanol : acetonitrile (5 : 3 : 2 v/v/v). Linearity ranges were 2-20 mug ml(-1), 2-36 mug ml(-1) and 0.5-20 mug ml(-1) for lansoprazole, omeprazole and pantoprazole, respectively. The corresponding recoveries were 100.61+/-0.84%, 100.50+/-0.80% and 99.78+/-0.88%. The minimum detection limits were 0.55, 0.54 and 0.03 mug ml(-1) for lansoprazole, omeprazole and pantoprazole, respectively. The method could be successfully applied to the determination of pure, laboratory prepared mixtures and pharmaceutical dosage forms. The results obtained were compared with the reported methods for lansoprazole and pantoprazole or the official U.S.P method for omeprazole.     

Liquid chromatographic determination of cobalt(II), copper(II) and iron(II) using 2-thiophenaldehyde-4-phenyl-3-thiosemicarbazone as derivatizing reagent

The complexing reagent 2-thiophenaldehyde-4-phenyl-3-thiosemicarbazone (TAPT) was examined for high performance liquid chromatographic (HPLC) separations of cobalt(II), copper(II) and iron(II) or cobalt(II), nickel(II), iron(II), copper(II) and mercury(II) as metal chelates on a Microsorb C-18, 5-mum column (150x4.6 mm i.d.) (Rainin Instruments Woburn, MA, USA). The complexes were eluted isocratically with methanol:acetonitrile:water containing sodium acetate and tetrabutyl ammonium bromide (TBA). UV detection was at 254 nm. The solvent extraction procedure was developed for simultaneous determination of the metals, with detection limits within 0.5-2.5 mug ml(-1) in the final solution. The method was applied for the determination of copper, cobalt and iron in pharmaceutical preparation.     

Direct determination of selenium in a wild fruit juice by electrothermal atomic absorption spectrometry

A matrix modifier composed of platinum and nickel is proposed for the determination of selenium in a wild fruit juice made from Lantingguo (Vuccinium uliginosam). Five matrix modifiers (copper/nickel, palladium/magnesium, platinum/magnesium, platinum/nickel and platinum/copper) for suppressing the interference effects of seven co-existing elements (potassium, phosphorus, calcium, magnesium, manganese, zinc and iron) in a wild juice were studied and a matrix modifier composed fro;m 10 mug of platinum and 200 mug of nickel was found to give the best performance. Selenium in three juices was determined by electrothermal atomic absorption spectrometry employing the proposed matrix modifier without matrix preseparation. The relative standard deviation was 14% for 0.20 mg l(-1) of selenium. The recoveries were 95-110%. A characteristic mass was 28 pg.     

The use of phenylfluorone in the presence of cetylpyridinium chloride and Triton X-100 for the spectrophotometric determination of copper(II) in blood serum

A simple and sensitive spectrophotometric method for determination of copper(II) is based on the formation of a blue coloured complex of Cu(II) with 9-phenyl-2,3,7-trihydroxy-6-fluorone (PF) in the presence of cetylpyridinium chloride (CP) and Triton X-100, has been developed. Optimum concentrations of PF, CP, Triton X-100 and pH ensuring maximum absorbance were defined. The complex Cu(II)-PF-CP-Triton X-100 shows maximum absorbance at 595 nm with a molar absorptivity value of 9.67x10(4) l mol(-1) cm(-1). The detection limit of the method is 0.028 mug ml(-1). Beer's law is obeyed for copper concentrations in the range 0.04-0.4 mug ml(-1). The studies of the effect of foreign ions on determination of copper, show that the selectivity of the method is poor. The cations of alkali metals and anions Br(-), Cl(-), I(-), F(-), NO(2)(-), NO(3)(-), CH(3)COO(-), SO(4)(2-), S(2)O(3)(2-), PO(4)(3-), citrates (examined in 1000-fold molar excess over copper) do not affect the determination. All cations forming complexes with PF have an interfering effect. The statistical evaluation of the method was carried out for six determinations using 10 mug of Cu and the following results were obtained: the standard deviation, SD=0.042, the confidence interval mu(95)=10.1+/-0.1 mug Cu. The method has been applied for determination of copper in blood serum.     

Extraction with long-chain amines-V Colorimetric determination of cobalt with nitroso-R salt

The colorimetric determination of cobalt with nitroso-R salt (NRS) has been modified and improved by the introduction of extraction of the Co-NRS chelate into a chloroform solution of trioctylmethylammonium chloride. Ammonium phosphate, fluoride and mainly citrate were used for masking iron, nickel, copper and calcium, which under the described conditions do not interfere even in 2000-fold excess. The method is very sensitive and permits determination of about 1 mug of cobalt per ml of the extractant.     

Chemical reduction and spectrophotometric determination of silver, copper and nickel

Silver(I), copper(II) and nickel(II) can be reduced to the metallic state by formaldehyde at pH 11, chromium(II) in 2.5M sulphuric acid, and borohydride at pH 5.5-6.0, respectively. Reoxidation of these metals with iron(III) in the presence of Ferrozine enables their determination at concentration below 1 mug/ml by measurement of the absorbance of the iron(II)-Ferrozine complex at 562 nm, with a precision better than 3%. The apparent molar absorptivities for silver, copper and nickel are 2.78 x 10(4), 5.56 x 10(4) and 5.58 x 10(4) l.mole(-1).cm(-1), respectively. The average thickness of silver films on glass surfaces can be determined in the way.     

Flow injection fluorimetric determination of thiamine and copper based on the formation of thiochrome

The reaction, involving the oxidation of thiamine by copper(II) in basic solutions to fluorescent thiochrome, has been adapted to the determination of thiamine by flow-injection analysis. Linear calibration graphs are obtained between 0.30 and 6.02 mug/ml with a sampling rate of 50 samples/hr and a relative standard deviation of 0.53%. This reaction has also been adapted to the determination of copper(II) over the range 0.5-5.0 mug/ml. The applicability of both methods for determination of thiamine and copper is demonstrated by investigating the effect of potential interferences and by the analysis of real samples (pharmaceuticals for thiamine and ores and alloys for copper).     

The separation of W(V) from HCl-KSCN medium on polyurethane foam sorbents for its spectrophotometric determination in steels and silicates

A simple procedure for selective sorption of tungsten is described. The method involves reduction of W(VI) to W(V) with tin(II) chloride (2%, w/v) at 8-9M hydrochloric acid, formation of the W(V)-SCN complex with 0.2M KSCN and its sorption on polyurethane foam within 20 min. The sorbed complex is then eluted with acidified acetone (1 ml of 1M hydrochloric acid and 8 ml of acetone) followed by addition of 1 ml of 0.1M KSCN to the eluent. The method has been applied to the spectrophotometric determination of tungsten in steels and silicates by measuring the absorbance of the eluted solution at 400 nm. Beer's law is obeyed for the range 0.1-12 mug W/ml. Other elements, e.g., Co(III) (50 mug/ml), Cu(II) (10 mug/ml), Ti(IV) (20 mug/ml), V(V) (10 mug/ml) and Mo(VI) (0.5 mug/ml) have no effect on the method. Interference of copper, up to 100 mug/ml has been eliminated by masking with thiourea and that due to molybdenum by prior separation with thioglycollic acid on PUF. The method has been verified with standard samples.     

Heterocyclic dithiophosphates as analytical reagents Indirect extraction-spectrophotometric determination of silver in copper concentrates and ores

The proposed method is based on the exchange reaction between the complex of copper(II) with 4,7-dimethyl-2-thiol-2-thion-1,3,2-dioxophosphorinan (DOPh(III)) in toluene and an aqueous solution of silver(I). The decrease in the absorbance of the Cu(DOPh(III))(2) solution is proportional to the silver(I) concentration for 5-90 mug of silver in 5 ml of toluene extract and 5-30 mug in 10 ml of toluene extract. The method is applied to the determination of silver in copper concentrates and ores.     

A spectrophotometric method for the determination of copper ions and its application to the co-precipitation of copper in the crystallization of sodium

The molar absorptivity of the cyanide complexes [Cu(CN)(3)](2-) and [Cu(CN)(4)](3-), at their isosbestic wavelength (235 nm) is 1.13 x 10(3) l.mole(-1)mm.(-1) and can be used for the quantitative determination of micro-amounts of copper in the ppm range. The determination of 1-10 mug of Cu(2+) per g of NaCl, or 0.25-2.5 mug ml , is described in detail. The co-precipitation of copper with NaCl crystallizing from aqueous solutions has been studied by this method.     

Determination of iron and nickel by flame atomic absorption spectrophotometry after preconcentration on Saccharomyces cerevisiae immobilized sepiolite

Iron and nickel have been preconcentrated on Saccharomyces cerevisiae immobilized sepiolite and determined by flame atomic absorption spectrophotometry (FAAS). Preconcentration studies were conducted by the column method. Effect of pH, amount of adsorbent, elution solution, flow rate and interfering ions on the recovery of the analytes have been investigated. Recoveries of Fe and Ni were 95+/-1 and 99.5+/-0.1%, respectively, at 95% confidence level. The breakthrough capacities of analytes were also investigated and found to be 0.042 mmol g(-1) for Fe and 0.055 mmol g(-1) for Ni. The proposed method was applied to the determination of iron and nickel in brass (NBS SRM 37e). The detection limit of iron and nickel were found as 0.065 and 0.087 mug ml(-1), respectively. The direct determination of trace metals by flame atomic absorption spectrometry (FAAS) is limited and difficult because of low concentration and/or matrix interferences. The proposed method is excellent for the determination of trace metal in matrixes, such as metal alloys.     

The use of 1-[pyridyl-(2)-azo]-naphthol-(2) in the presence of TX-100 and N,N'-diphenylbenzamidine for the spectrophotometric determination of copper in real samples

A simple and sensitive field detection and spectrophotometric method for determination of copper described herewith is based on the formation of a red coloured species of copper(II) with 1-[pyridyl-(2)-azo]-naphthol-(2) (PAN), TX-100 and N,N'-diphenylbenzamidine (DPBA) at pH range 7.8-9.4. The red coloured Cu(II)-PAN-(TX-100)-DPBA complex in chloroform shows maximum absorbance at 520 nm with molar absorptivity value of 1.14x10(5) l mol(-1) cm(-1). The detection limit of the method is 2 ng ml(-1) organic phase. The system obeys Beer's law up to 0.6 mug Cu(II) ml(-1) in organic solution. Most of the common metal ions generally found associated with copper do not interfere. The repeatability of the method was checked by finding relative standard deviation (RSD) (n=10) value for solutions each containing 0.2 mug ml(-1) of Cu(II) and the RSD value of the method was found to be 1.5%. The validity of the method has been satisfactorily examined for the determination of copper in soil and airborne dust particulate samples.     

Photometric determination of cobalt with nitroso-R-salt

The chelate is quantitatively formed only in the pH range 6.5-7.5. Despite the large stability constant, a large excess of reagent is required to suppress interferences. The most suitable wavelength for the photometric measurement is 500 nm, where the molar absorptivity is 1.607 x 10(4) 1.mole(-1). cm(-1). The procedure given allows determination of 8 x 10(-4)% Co in a l-g sample. The standard deviation for cobalt is 2.1 mug/100 ml (f = 19). Applications to analysis of iron and steel, nickel, copper, ores and silicates are given.     

Highly sensitive colour-reaction of nickel with a new chromogenic reagent benzothiaxolyldiazoaminoazobenzene and its application

The synthesis of benzothiaxolyldiazoaminoazobenzene (BTDAB) is described, and a simple, rapid and sensitive procedure for spectrophotometric determination of nickel has been developed. At pH 9.4, in the presence of emulsifier p-octylpolyethyleneglycol phenylether (OP), the reagent reacts with nickel to form a red 1:3 (metal:ligand) complex. The nickel-BTDAB complex exhibit an adsorption maximum at 550 nm with an apparent molar absorptivity of 1.96 x 10(5) 1 mol(-1) cm(-1), Beer's law is obeyed for nickel in the range 0-7 mug per 25 ml. The proposed method has been applied to the determination of nickel in aluminum alloy with satisfactory results.     

Spectrophotometric determination of nickel in copper-base alloy with 2-(2-thiazolylazo)-p-cresol

A spectrophotometric method for determination of nickel in copper-base alloy with 2-(2-thiazolylazo)-p-cresol (TAC) is described. The interferences of foreign ions can be eliminated by masking with a mixture of sodium tartrate and sodium thiosulphate. The nickel-TAC complex has low solubility in water, but is soluble in aqueous ethanol. Beer's law is obeyed for 20-70mug of nickel in 50 ml of solution, at pH 5.7. The molar absorptivity at 580 nm is 2.6 x 10(4)l.mole(-1).cm(-1). The method has been applied successfully to determination of nickel in reference samples.     

Preconcentration of trace nickel with the ion pair of disodium 1-nitroso-2-naphthol-3,6-disulfonate and tetradecyldimethylbenzylammonium chloride on microcrystalline naphthalene or by the column method and determination by third derivative spectrophotometry

Nickel is quantitatively retained by disodium 1-nitroso-2-naphthol-3,6-disulfonate (nitroso-R salt) and tetradecyldimethylbenzylammonium chloride (TDBA(+)Cl(-)) on microcrystalline naphthalene in the pH range 5.4-12.1 from large volumes of aqueous solutions of various alloys and biological samples. After filtration, the solid mass consisting of the nickel complex and naphthalene was dissolved with 5 ml of dimethylformamide (DMF) and the metal was determined by third derivative spectrophotometry. Nickel complex can alternatively be quantitatively adsorbed on tetradecyldimethylbenzylammonium-naphthalene adsorbent packed in a column and determined similarly. The detection limit is 10 ppb (signal to noise ratio 2) and the calibration curve is linear from 30 to 5.4x10(3) ppb in dimethylformamide solution with a correlation coefficient of 0.9997 by measuring the distance d(3)A/dlambda(3) between lambda(1) (537 nm) and lambda(2) (507 nm). Eight replicated determinations of 2.5 mug of nickel in 5 ml of dimethylformamide solution gave a mean intensity (peak-to-peak signal between lambda(1) and lambda(2)) of 0.339 with a relative standard deviation of +/-0.87%. The sensitivity of the method is 0.677 ml/mug found from the slope (d(3)A/dnm(3)) of the calibration curve. Various parameters such as the effect of pH, volume of aqueous phase and interference of a number of metal ions on the determination of nickel has been studied in detail to optimize the conditions for nickel determination in various alloys and biological samples.     

Application of photochemical inhibition in flow injection systems: Determination of epinephrine and L-dopa

An automated procedure for the photochemical determination of epinephrine and L-dopa has been developed. It is based on the strong inhibition by these catecholamines on the photochemical reaction between phloxin and ethylenediaminetetraacetic. The proposed flow-injection method allows the fluorimetric determination of epinephrine in the range 1.9-26.4 mug/ml and of L-dopa in the range of 1.5-12.7 mug/ml, with a sampling frequency of 35 samples/hr. The method was applied successfully to the determination of body catecholamines in pharmaceutical preparations.     

Spectrophotometric multicomponent determination of sunset yellow, tartrazine and allura red in soft drink powder by double divisor-ratio spectra derivative, inverse least-squares and principal component regression methods

Double divisor-ratio spectra derivative (graphical method), classical least-squares and principal component regression (two numerical methods) methods were developed for the spectrophotometric multicomponent analysis of soft drink powders and synthetic mixtures containing three colorants without any chemical separation. The graphical method is based on the use of derivative signals of the ratio spectra using double divisor. In this method, the linear determination ranges were 2-8 mug ml(-1) sunset yellow, 4-18 mug ml(-1) tartrazine and 2-8 mug ml(-1) allura red in 0.1 M HCl. In the numerical methods, a training set was randomly prepared by using 18 samples containing between 0 and 8 mug ml(-1) of sunset yellow, 0-18 mug ml(-1) of tartrazine and 0-8 mug ml(-1) of allura red. The chemometric calibrations were calculated by using the prepared training set and its absorbances at seven points (from 375.0 to 550.0 nm) in the spectral region 325-584 nm. The proposed methods were validated by using synthetic ternary mixtures and applied to the simultaneous determination of three colorants in soft drink powders. The obtained results were statistically compared with each other.     

Flow-injection chemiluminometric analysis of some benzamides by their sensitizing effect on the cerium-sulphite reaction

A simple, highly sensitive chemiluminescent method using flow injection is described for the determination of three substituted benzamides, namely: sulpiride, sultopride and tiapride. The method is based on the sensitizing effect of these drugs on the chemiluminometric oxidation of sulphite by cerium(IV). The different experimental parameters affecting the chemiluminescence intensity were carefully studied and incorporated into the procedure. The method permits the determination of 0.05-2.5 mug ml(-1) sulpiride, 0.01-2.5 mug ml(-1) sultopride hydrochloride and 0.01-1.5 mug ml(-1) tiapride hydrochloride with minimum detectability of 0.01 mug ml(-1). The method was applied to the determination of these benzamides in pharmaceutical preparations and biological fluids.