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.     

Separation and preconcentration of metal ions and their estimation in vitamin, steel and milk samples using o-vanillin-immobilized silica gel

o-Vanillin-immobilized silica gel has been used for the adsorption and estimation of copper, cobalt, iron and zinc by both batch and column techniques. Metal ions were quantitatively retained on the column packed with immobilized silica gel in the pH range 4.0-6.0 for Cu, 5.0-6.0 for Co, 4.5-6.0 for Fe and 6.0-8.0 for Zn. The distribution coefficient D determined for each metal was as follows (ml g(-1)): Fe, 5.4x10(2); Cu, 4.9x10(2); Zn, 4.4x10(2); Co, 3.8x10(2). Methods have been developed to estimate zinc, copper and cobalt in milk, steel and vitamin samples, respectively.     

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.     

Separation of antimony(III) with iodide and dithizone by sorption on polyurethane foam from sulphuric acid medium for its spectrophotometric determination in glasses

A method for quantitative separation of antimony(III) by sorption on polyether based polyurethane foam and its spectrophotometric determination has been described. The method involves formation of a pink-red complex of antimony(III) with iodide (0.045M) and dithizone (2.3 x 10(-5)M) in 0.25-0.75M H(2)SO(4) medium, sorption of the complex on polyurethane foam (within 45 min) at room temperature followed by its elution with acidified acetone (acetone containing 0.008% H(2)SO(4)) and spectrophotometric measurement at 507.2 nm ( = 2.56 x 10(4) l mol cm). The method obeys Beer's law from 0.1 to 6.0 mug antimony(III). Tolerance limits of other ions are Co (100 mug), Ni (100 mug), Fe (10 mug), Cu (0.5 mug), Sn (20 mug), Zn (100 mug), As (100 mug), Mn (200 mug), Pb (50 mug), Ti (100 mug), V (50 mug), etc. Interference by iron and copper have been eliminated by treating with KOH prior to the extraction of antimony. The method has been standardized with glass samples spiked with known amounts of antimony and applied to the determination of antimony in various glasses.     

Column chromatographic preconcentration of palladium in alloys with 9,10 phenanthrenequinonemonoxime-naphthalene

A solid chelating compound phenanthrenequinonemonoxime (PQM) supported on naphthalene provides a rapid, sensitive and economical means of preconcentration and separation of palladium from standard solutions and from synthetic samples. Palladium forms a complex with PQM supported on naphthalene in a column at pH 2.2-5.4 with a flow-rate of 1 ml/min. The metal complex and naphthalene are dissolved out from the column with 5 ml of CHCl(3) and the absorbance is measured at 430 nm or 500 nm against a reagent blank. Beers law is obeyed in the concentration range 3.0-56.0 mug and 6.0-42.0 mug at 430 nm and 500 nm respectively. The molar absorptivities are 2.10 x 10(4) and 1.69 x 10(4) 1.mole(-1).cm(-1) at 430 and 500 nm respectively.     

Spectrophotometric determination of chromium(III) and rhodium(III) after extraction with oxine into molten naphthalene

Conditions have been developed for the extraction of chromium(III) and rhodium(III) as their 8-hydroxyquinolinates into molten naphthalene. The naphthalene is allowed to solidify, separated by filtration, dried with filter paper and dissolved in chloroform. The solution is diluted to 10 ml and its absorbance measured at 410 nm for chromium and 425 nm for rhodium, against a reagent blank. In both cases the solution is stable for 24-36 hr. Beer's law is obeyed over the range of 2.7-48.6 mug of chromium or 2.7-57.5 mug of rhodium in 10 ml of the chloroform solution. The molar absorptivity is 3 x 10(3) l. mole(-1) . cm(-1) for chromium and 3.6 x 10(4) for rhodium. Solutions containing 27.0 mug of chromium or 10.95 mug of rhodium give a mean absorbance of 0.140 and 0.395 respectively, with standard deviations of 0.002(2) and 0.004(7). Most metal ions that form oxinates may interfere, but can be removed beforehand by normal liquid-liquid extraction.     

Preconcentration of cobalt with N-(dithiocarboxy)sarcosine and amberlite xad-4 resin

Cobalt reacts with N-(dithiocarboxy)sarcosine (DTCS) to form a 1:3 Co:DTCS complex which is so stable that after its formation no decomposition occurs even in 4M hydrochloric acid. The complex is sorbed on a column of Amberlite XAD-4 copolymer from an acidic solution and eluted with 10 ml of a 1:1:3 v v mixture of 1.0M ammonia solution (pH = 9), 0.1M EDTA and methanol. The absorbance of the eluted chelate is measured at 320 nm against water ( = 2.15 x 10(4) l.mole(-1).cm(-1)). The recovery of cobalt from 1 litre of tap-water or sea-water is quantitative. The effect of diverse ions can be eliminated by the addition of EDTA after chelation of the cobalt. The copper complex with DTCS is partly sorbed on the column because of its slow rate of decomposition by EDTA, but most of the copper chelate sorbed can be eluted with hydrochloric acid and any co-eluted with the cobalt chelate can be completely decomposed by heating the eluate. Cobalt enrichment factors of at least 100 are obtained, so the method is applicable to the determination of cobalt at the ng ml level.     

Preconcentration of trace cobalt with the ion pair of 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol and tetraphenylborate onto microcrystalline naphthalene or column method and its determination by derivative spectrophotometry

Cobalt-2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP)-tetraphenylborate ion associated complex is quantitatively adsorbed on microcrystalline naphthalene in the pH range 3.5-9.5 from a fairly large volume of the aqueous samples (preconcentration factor ~30). After filtration, the solid mass consisting of the cobalt complex and naphthalene was dissolved with 5 ml of dimethylformamide (DMF) and the metal determined by first-derivative spectrophotometry. The cobalt-5-Br-PADAP complex can alternatively be quantitatively retained on ammonium tetraphenylborate-naphthalene adsorbent filled in a column (preconcentration factor 120) in the same pH range and determined similarly. The detection limit is 30 ppb (signal-to-noise ratio=2) and the calibration curve is linear over 0.3-8.0 mug of cobalt in 5 ml of the final DMF solution. Eight replicate determinations of 1.0 mug of cobalt gave a mean peak height of 0.208 (at 611.5 nm) with a relative standard deviation of 1.2%. The sensitivity of the method is 1.04 (dA/dnm) ml mug(-1) found from the slope of the calibration curve. The interference of a large number of anions and cations on the determination of cobalt has been studied and the optimized conditions developed were utilized for its trace determination in various standard alloys and biological samples.     

Silaned glass beads for the preconcentration and spectrophotometric determination of cobalt with 2-(2-pyridylazo)-5-diethylaminophenol

Silaned glass beads are applied for the preconcentration and spectrophotometric determination of cobalt with 2-(2-pyridylazo)-5-diethylaminophenol (PADAP). Traces of cobalt are collected as the coloured PADAP complex on a column of the beads, and the complex is then eluted with a small volume of ethanol-hydrochloric acid mixture and the absorbance of the eluate is measured at 575 nm. The cobalt can easily be concentrated by a factor of 50-500 in this way, and 0.1-2 mug of cobalt in 100 ml of sample solution can be determined reproducibly. High concentrations of Fe(III), Cr(III), Pb, Zn, Cu(II), Mn(II), Cd, Al, Ca and Mg can be tolerated but Pd(II) interferes.     

Spectrophotometric determination of traces of iron after extraction of Fe(II)-phenanthroline complex on polyurethane foam

A spectrophotometric method for the determination of traces of iron in glass and ceramic materials has been developed. The method involves formation of the Fe(II)-phenanthroline complex at pH 3-4 in aqueous medium, followed by its selective extraction and preconcentration on polyurethane foam from 2.5M perchloric acid and finally elution of the complex with acetone for spectrophotometric measurement at 510 nm. A wide linearity range from 0.05 to 3 mu g/ml Fe is obtained with the method. Co, Cu and Ni have no significant effect when they are present in the weight ratios Fe:Co < 1:2, Fe: Cu < 1:10 and Fe: Ni < 1:50. The method yielded satisfactory results when applied to various glass and ceramic samples.     

Reversed phase foam chromatography : Separation of iron from copper,cobalt and nickel in the tri-n-butyl phosphate-hydrochloric acid system

The separation of iron from cobalt, copper and nickel by reversed-phase foam chromatography was investigated. The distribution of Fe, Co and Cu in TBP-HCl and TBP(polyurethane foam)-HCl systems was measured. Iron can be separated from the three other metals on polyether-type polyurethane foam columns loaded with TBP. The break-through curve of iron on TBP (polyurethane foam) columns was measured. The column was found suitable for the separation of ⁵⁸Co and ⁵⁹Fe isotopes.     

Liquid chromatographic determination of chelates of cobalt (II), copper (II) and iron (II) with 2-thiophonaldehyde-4-phenyl-3-thiosemicarbazone

Summary A new chelating reagent 2-thiophenaldehyde-4-phenyl-3-thiosemicarbazone (TAPT) has been 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 C₁₈, 5μm column (250×4 mm i.d.) The chelates were eluted isocratically with methanol: acetonitrile: water containing sodium acetate and tetrabutylammonium bromide (TBA), and detected at 254 nm. A solvent extraction procedure was developed for simultaneous determination of the metals with detection limits within 0.02–2.5 μ g.mL⁻¹. The method was applied to the determination of copper, cobalt and iron in natural waters.     

Analysis of metals by solid-liquid separation after liquid-liquid extraction spectrophotometric determination of palladium(II) by extraction of palladium dimethylglyoximate with melted naphthalene

A method of liquid-liquid extraction of palladium di-methylglyoximate with molten naphthalene followed by solid-liquid separation is successfully applied to palladium. The complex between palladium and dimethylglyoxime is easily extracted into molten naphthalene. After extraction, the very fine solidified naphthalene crystals are dissolved in chloroform, and the absorbance of the resultant solution is measured at 370 nm against a reagent blank. Beer's law is obeyed for 30-370 mug of palladium in 10 ml of chloroform, and the molar absorptivity is calculated to be 1.72 x 10(4) l.mole.(-1)mm(-1). Various alkali metal salts and metal ions do not interfere. The interference of nickel(II) is overcome by the extraction at pH 2, and that of iron(III) by masking with EDTA or by reduction to iron(II). The method is rapid and accurate.     

Study on the solid phase extraction of Co(II)-QADEAB chelate with C(18) disk and its application to the determination of trace cobalt

A sensitive, selective and rapid method has been developed for the determination mug l(-1) level of cobalt based on the rapid reaction of cobalt(II) with 2-(2-quinolylazo)-5-diethylaminobenzoic acid (QADEAB) and the solid phase extraction (SPE) of the colored chelate with Waters Porapak(R) Sep-Park C(18) disk. The QADEAB can react with Co(II) in the presence of pH 3.8 acetic acid-sodium acetate buffer solution and cetyl trimethylammonium bromide (CTMAB) medium to form a violet chelate of a molar ratio 1:2 (cobalt to QADEAB). This chelate can retained on Waters Porapak(R) Sep-Park C(18) disk quantitatively when they passed the disk as aqueous solution. After the enrichment finished, the retained chelate can be eluted from disk by 2.5 ml of ethanol (contain 5% acetic acid). In the measured solution, the molar absorptivity of the chelate is 1.58x10(5) l mol(-1) cm(-1)at 635 nm, and Beer's law is obeyed in the range of 0.01-0.4 mug ml(-1). The relative standard deviation for 11 replicate sample of 0.01 mug ml(-1) level is 2.23%. The detection limit is 0.01 mug l(-1) (in original samples). This method can be applied to the determination of mug l(-1) level of cobalt in drinking water with satisfactory results.     

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.     

Oximidobenzotetronic acid — a sensitive spot test reagent for iron(II), cobalt(II) and copper(II)

Summary Oximidobenzotetronic acid is suggested as a sensitive spot test reagent for iron(II), cobalt(II) and copper(II) in the presence of commonly occuring cations.

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Zusammenfassung Oximidobenzotetronsäure (3-Ntroso-4-hydroxycumarin) wird als empfindliches Tüpfelreagens zum Nachweis von Fe(II), Co(II) und Cu(II) in Gegenwart anderer Kationen vorgeschlagen.

     

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.     

Ammonium tetraphenylborate-naphthalene adsorbent for the preconcentration and trace determination of iron in alloys and biological samples using 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol by third derivative spectrophotometry

A solid ion-pair material produced from ammonium tetraphenylborate on naphthalene (ATPB-naphthalene) provides a simple, rapid, economical and selective technique for preconcentrating iron from approximately 500 ml of aqueous solution of standard alloys and biological samples. Iron reacts with 2-(5-bromo-2-pryidlazo)-5-diethylaminophenol (5-Br-PADAP) to form a water-soluble cationic complex. When the aqueous solution of this cationic species in the pH range 3.2-8.5 is passed over the adsorbent ATPB-naphthalene at a flow rate of 1 ml min(-1), it is quantitatively retained on naphthalene as an uncharged ion-associated complex. The solid mass from the column was dissolved out with 5 ml of dimethylformamide (DMF) and iron is determined by third derivative spectrophotometry by measuring the signal d(3)A/ dlambda(3) between lambda(2)(773 nm) and lambda(3)(737 nm). The calibration curve is linear over the concentration range 0.10-25.0 mug of iron in 5 ml of DMF solution. Eight replicate determinations of 5 mug of iron gave a mean intensity (peak-to-peak signal between lambda(2) and lambda(3)) of 1.534 with a relative standard deviation of 0.90%. The sensitivity of the method is 0.307 (d(3)A/dnm(3) )/mug found from the slope of the calibration curve. The interference of a large number of anions and cations has been studied and the optimized conditions developed were utilized for the trace determination of iron in various standard alloys and biological samples.     

Potassium hexacyanoruthenate(II) as an analytical reagent for iron

Fe(III) undergoes a reaction with colourless Ru(CN)(4-)(6) to produce an intensely violet-blue complex that absorbs at 550 nm and obeys Beer's law over the iron concentration range 0.04-2 mug/ml in acidic medium. Some common cations and anions are tolerable at low concentrations. The procedure is applicable for determination of total iron in potable water. Destruction of organic matter is required for contaminated surface waters or soil samples.     

Derivative spectrophotometry in the determination of metal ions with 4-(pyridyl-2-azo)resorcinol (PAR)

Derivative spectrophotometry has been applied for the elimination of the mutual spectral interferences and the analysis of binary, ternary and quaternary mixtures of complexes of microgram amounts of divalent ions of cobalt, copper, lead, manganese, nickel, zinc and iron with 4-(pyridyl-2-azo)resorcinol (PAR) in the range of 0.05-1 microg/ml (0.2-4 microg/ml for lead). The first derivative spectra can be used for the determination of both components in the majority of binary mixtures except of Cu(II) and Co(II) and systems containing Fe(II). The second and the third derivative spectra allow to determine one constituent in some ternary and quaternary mixtures.