Simultaneous determination of lead and cadmium in various environmental and biological samples by differential pulse polarography after adsorption of their morpholine-4-carbodithioates onto microcrystalline naphthalene or morpholine-4-dithiocarbamate-CTMAB-naphthalene adsorbent

A highly selective, sensitive and rapid differential pulse polarographic method (DPP) has been developed for the simultaneous estimation of trace amounts of lead and cadmium in standard alloys, biological and environmental samples. The morpholine-4-carbodithioates of the samples were absorbed on microcrystalline naphthalene in the pH range of 5-10 for lead and 3.4-11 for cadmium. The metal complexes were desorbed with 10 ml of 1M HCl and determined simultaneously with a differential pulse polarograph. These metals can alternatively be quantitatively adsorbed on morpholine-4-dithiocarbamate-cetyltrimethylammonium bromide-naphthalene adsorbent packed in a column and determined similarly. The detection limits are 0.14 ppm for Pb and 0.014 ppm for Cd at minimum instrumental settings (signal-to-noise ratio = 2). The linearity is maintained in the concentration ranges of Pb, 0.7-15 ppm and Cd, 0.07-10 ppm with a correlation factor of 0.9997 and relative standard deviations of 0.95 and 0.81%, respectively. Various parameters such as the effect of pH, volume of aqueous phase, and interference of a number of metal ions on the estimation of lead and cadmium have been studied in detail to optimize the conditions for their simultaneous estimation in various biological and environmental samples.     

Preconcentration of Indium(III) from Complex Materials After Adsorption of Its Morpholine-4-dithiocarbamate on Naphthalene or Using Morpholine-4-dithiocarbamate-cetyltrimethylammonium Bromide-naphthalene Adsorbent

Abstract

A highly selective, sensitive and rapid differential pulse polarographic method has been developed for the estimation of trace amounts of indium in standard alloy, ore, synthetic and environmental samples. The morpholine-4-dithiocarbamate of indium(III) is adsorbed on microcrystalline naphthalene in the pH range 3.5–6.4. The metal complex is desorbed with HCl and determined with a differential pulse polarograph (DPP). This metal may alternatively be quantitatively retained on morpholine-4-dithiocarbamate-cetyltrimethylammonium bromidenaphthalene adsorbent packed in a column at a flow rate of 0.5–5.0 ml/min and determined similarly. The detection limit is 0.10 ppm at the minimum instrumental setting (signal to noise ratio = 2). Indium has been determined in the concentration range 0.70–15.0 ppm with a correlation factor of 0.9996 and a relative standard deviation of 0.76% (n = 8). In the column method, the linearity is maintained in the concentration range 0.70–8.5 ppm with a correlation factor of 0.9994 and a relative standard deviation of 0.89% (n = 8). Various parameters, such as the effect of pH, volume of aqueous phase, reagent, and naphthalene concentrations and interference of a large number of metal ions and anions on the estimation of indium have been studied in detail to optimize the conditions for its trace determination in various complex materials.     

Differential pulse polarographic determination of tin in alloys and environmental samples after preconcentration with the ion pair of 2-nitroso-1-naphthol-4-sulfonic acid and tetradecyldimethylbenzylammonium chloride onto microcrystalline naphthalene or by column method

A highly selective, sensitive, rapid and economical differential pulse polarographic method has been developed for the determination of trace amount of tin in various standard alloys and environmental samples after adsorption of its 2-nitroso-1-naphthol-4-sulfonic acid-tetradecyldimethylbenzylammonium chloride on microcrystalline naphthalene in the pH range of 8.7-10.6. After filtration, the solid mass is shaken with 8-10 ml of 3.5 M hydrochloric acid and tin is determined by differential pulse polarography (DPP). Tin can alternatively be quantitatively adsorbed on 2-nitroso-1-naphthol-4-sulfonic acid-tetradecyldimethylbenzylammonium-naphthalene adsorbent packed in a column and determined similarly. The detection limit is 0.15 mug ml(-1) (signal to noise ratio=2) and the linearity is maintained in the concentration range 0.5-220 mug ml(-1) with a correlation coefficient of 0.9995 and relative standard deviation of +/-0.88%. Characterization of the electroactive process included an examination of the degree of reversibility. Various parameters such as the effect of pH, volume of aqueous phase and interference of a number of metal ions on the determination of tin has been studied in detail to optimize the conditions for determination in standard alloys and environmental samples.     

Selective extraction and photometric determination of trace vanadium with cinnamohydroxamic acid in MIBK and its application to steel and rock ore analysis

A sensitive and selective photometric method for the trace determination of vanadium with cinnamohydroxamic acid extracted from 1.8 M HCl in methyl isobutyl ketone is described. The wine-red chelate formed under an optimum acidity of 1.3-2.6 M HCl absorbs with a maximum at 525 nm. Beer's law is obeyed in the range 0-8 ppm of vanadium(V) and the optimum range of determination of vanadium is found to be 1-8 ppm. The molar absorptivity and Sandell's sensitivity are 6.0 x 10(3) l mol(-1) cm(-1) and 0.0086 mug cm(-2) of vanadium(V) at 525 nm. The photometric determination of trace amounts of vanadium in materials such as alloys, minerals and rock ores is also reported. The solvent extraction methods are simple, rapid and highly selective with fluoride used as a masking agent for Fe and Ti. The standard deviations are minimal and the mean error is only 0.015%.     

Differential Pulse Polarographic Determination of Gallium and Niobium in Samples After Preconcentration of Their Quinolin-8-Olate Complexes on Microcrystalline Naphthalene

Abstract

Gallium and niobium react with quinolin-8-ol to form water insoluble complexes which are quantitatively adsorbed on microcrystalline naphthalene from the large volume of their aqueous solutions in the pH range of 3.5 - 8.2 and 6.2 - 9.4, respectively. After filtration, the metal complexes were desorbed with 10 ml of HCl (1M for Ga and 11 M for Nb) and determined by using a differential pulse polarograph (DPP). The dissolved oxygen is removed by adding a few milliliters of 4% NaBH₄ solution in the case of gallium. The detection limits are 0.04 ppm for gallium and 0.05 ppm for niobium at the minimum instrumental settings (signal to noise ratio = 2). The linearities are maintained in the concentration range 0.1 - 5.0 ppm for gallium and 0.4 - 6.0 ppm for niobium with correlation factors of 0.9997 and 0.9996 and relative standard deviations of 0.81 and 0.95%, respectively.

Characterization of the electroactive process included an examination of the degree of reversibility. Various parameters such as the effect of pH volume of aqueous phase, reagent and naphthalene concentrations and the interference of a large number of anions and cations on the estimation of these elements were studied in detail. The method is found to be highly selective, fairly sensitive, rapid, simple and economical. It has been applied for the trace determination of gallium and niobium in various standard alloys and may be applied safely for the analyses of complex materials like environmental samples and ores.

     

Column preconcentration of titanium in aluminium and zinc alloys with oxalic acid-ascorbic acid and the ion-pair of sodium 1,2-dihydroxybenzene-3,5-disulphonic acid and tetradecyldimethylbenzylammonium chloride supported on naphthalene using spectrometry

A solid ion-pair compound produced from sodium 1,2-dihydroxybenzene-3,5-disulphonic acid (Tiron) and tetradecyldimethylbenzylammonium chloride(TDBA) supported on naphthalene in a simple glass-tipped funnel tube provides a simple adsorbent system for preconcentrating titanium from some alloys. Titanium reacts with Tiron to form a water-soluble coloured chelate anion which in turn forms a water-insoluble stable titanium/Tiron/TDBA complex with the ion-pair on the surface of naphthalene packed in a column. Titanium is quantitatively retained on the naphthalene in the presence of L-ascorbic acid and oxalic acid in the pH range 3.0-4.5 and at a flow-rate of 1 mil/min. The metal complex and naphthalene were dissolved from the column with 5 ml of dimethylformamide(DMF), and the absorbance of the solution was measured at 398 nm. A calibration graph was linear over the range 1-18 mug of titanium in 5 ml of the final DMF solution. The complex has a molar absorptivity of 1.39 x 10(4) l.mole(-1).cm(-1) and a sensitivity of 3.44 x 10(-3) mug/cm(2) for 0.001 absorbance. Eight replicate determinations for a sample containing 12 mug of titanium gave a mean absorbance of 0.697 with a relative standard deviation of 0.82%. The interference of various ions was studied and optimum conditions were developed for the determination of titanium in various aluminium and zinc alloys.     

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.     

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.     

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.     

Rapid and sensitive spectrophotometric determination of cerium(IV) with 2,4-dihydroxy benzophenone benzoic hydrazone

A simple and sensitive spectrophotometric method for the determination of cerium(IV) in an aqueous medium is reported. The metal ion formed a 1:1 orange-red coloured complex with 2,4-dihydroxy benzophenone benzoic hydrazone (DHBPBH) at pH 10.0 showing an absorption maximum at 400 nm. The molar absorptivity and Sandell's sensitivity of the method are found to be 2.0 x 10(4)1/mol/cm and 0.007 mug/cm(2), respectively. Beer's law is obeyed in the range 0.7-7.0 mug/ml. Titanium, vanadium and molybdenum do not interfere. The extent of interferences by other ions is presented. The method is applied for the determination of cerium in simulated rock samples.     

Spectrophotometric determination of nickel after separation by adsorption of its alpha-furildioxime complex on naphthalene

A new method is proposed for collecting traces of nickel from aqueous solution by precipitation as the alpha-furildioxime complex and adsorption of this onto microcrystalline naphthalene. The precipitate is collected, dried, and dissolved in chloroform, and the nickel is determined spectrophotometrically at 438 nm. The linear calibration range is 2-35 mug/10 ml. The molar absorptivity is 1.6 x 10(4) l. mole(-1). cm(-1). The main advantage is that the nickel is collected quantitatively after only a few seconds'shaking. The effect of varying pH, amount of reagent, naphthalene or buffer, shaking and standing time, and interferences have been investigated.     

Preconcentration of iron (III), cobalt (II) and copper (II) nitroso-R complexes on tetradecyldimethylbenzylammonium iodide-naphthalene adsorbent

Iron, cobalt and copper form coloured water soluble anionic complexes with disodium 1-nitroso-2-naphthol-3-6-disulphonate (nitroso R-salt). The anionic complex is retained quantitatively as a water insoluble neutral ion associated complex (M-nitroso R-TDBA) on tetradecyldimethylbenzylammonium iodide on naphthalene (TDBA(+)I(-)-naphthalene) packed column in the pH range of: Fe(III): 3.1-6.5, Co: 3.4-8.5 and Cu 5.9-8.0 when their solutions are passed individually over this adsorbent at a flow rate of 0.5-5.0 ml/min. The solid mass consisting of an ion associated metal complex along with naphthalene is dissolved out of the column with 5 ml dimethylformamide/chloroform and metals are determined spectrophotometrically. The absorbance is measured at 710 nm for iron, 425 nm for cobalt and 480 nm for copper. Beers law is obeyed in the concentration range 9.2-82 mug of iron, 425 nm for cobalt cobalt and 3.0-62 mug of copper in 5 ml of final DMF/CHCl(3) solution. The molar absorptivities are calculated to be Fe: 7.58 x 10(3), Co: 1.33 x 10(4) and Cu: 4.92 x 10(4)M(-1)cm(-1). Ten replicate determinations containing 25 mug of iron, 9.96 mug of cobalt and 3.17 mug of copper gave mean absorbances 0.677, 0.450 and 0.490 with relative standard deviations of 0.88, 0.98 and 0.92%, respectively. The interference of large number of metals and anions on the estimations of these metals has been studied. The optimized conditions so developed have been employed for the trace determination of these metals in standard alloys, waste water and fly ash samples.     

Photoinitiated gold sol generation in aqueous Triton X-100 and its analytical application for spectrophotometric determination of gold

Gold complex, HAuCl(4) has been transformed into pink-coloured stable gold sol having lambda(max) at 523 nm (in=3.06x10(3)1.mol(-1)cm(-1)) at room temperature in aqueous Triton X-100 (TX-100) upon photoirradiation. It is a very rapid and simple process and the absorbance at 523 nm is a direct measure of gold concentration. Beer's law is obeyed in the range of 0-150 ppm of gold. The relative standard deviation for 22.7 and 90.9 ppm of gold are 2.8 and 2.5% respectively. The 95% confidence limit (ten determinations) for 22.7 ppm of gold is 23.6+/-0.5 ppm. Sandell sensitivity is 6.44x10(-2) mug cm(-2). TX-100 acts both as a reducing agent and a stabilizer here. Statistical parameters, effects of TX-100 concentration, irradiation time and interferents are studied. The method is applicable for ore and synthetic mixture analysis.     

Harmonic analysis of vibrations of morpholine-4-ylmethylthiourea: a DFT, midinfrared and Raman spectral study

The FTIR and FT-Raman spectra of morpholine-4-ylmethylthiourea (MMTU) were recorded in the region of mid-IR (400-4,000 cm(-1)). Initial geometry generated from the standard geometrical parameters was relaxed without any constraint on the potential energy surface at MP2 and DFT levels adopting the standard 6-31++G and 6-311+G basis set. With the help of two specific scaling procedures the computed harmonic frequencies have been compared with the observed vibrational wave numbers of FTIR and FT-Raman spectra and assigned to different normal modes of the molecule. Most of the vibrational modes have wave numbers in the expected range. The appropriate theoretical spectrograms of the IR spectra of MMTU have been also constructed.     

Spectrophotometric determination of iron(III) dimethyldithiocarbamate (ferbam)

A spectrophotometric method was developed for the determination of ferbam (iron(III) dimethyldithiocarbamate) by converting it into an iron-phenanthroline complex, which was then absorbed on microcystalline naphthalene in the presence of tetraphenylborate, and the absorbance was measured at 515 nm against a reagent blank. The molar absorptivity of the complex was 1.2 x 10(4)l mol(-1)cm(-1). Ten replicate analyses of a sample solution containing 150 mug of ferbam gave a relative standard deviation of 0.84%. Beer's law was obeyed over the concentration range 22.4-372.9 mug of ferbam. The effects of various factors such as reagent concentration and naphthalene, shaking time and diverse ions were studied in detail. The method is sensitive and selective and can be applied to the direct determination of ferbam in commercial samples and in mixtures containing various other dithiocarbamates (e.g. ziram, zineb and maneb) in foodstuffs.     

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.     

Spectrophotometric determination of osmium with 1-phenyl-4,4,6-trimethyl-(1H,4H)-2-pyrimidinethiol and extraction into molten naphthalene

Conditions have been developed for the spectrophotometric determination of osmium with 1-phenyl-4,4,6-trimethyl-(1H,4H)-2-pyrimidinethiol after extraction of the complex into molten naphthalene. Beer's law holds for the concentration range of 4-77 mug of osmium in 10 ml of the final solution. The molar absorptivity is 1.33 x 10(4) l.mole(-1).cm(-1). The reagent is highly selective for osmium.     

Evaluation of luminol-H(2)O(2)-KIO(4) chemiluminescence system and its application to hydrogen peroxide, glucose and ascorbic acid assays

A novel chemiluminescence (CL) system was evaluated for the determination of hydrogen peroxide, glucose and ascorbic acid based on hydrogen peroxide, which has a catalytic-cooxidative effect on the oxidation of luminol by KIO(4). Hydrogen peroxide can be directly determined by luminol-KIO(4)-H(2)O(2) CL system. The detection limit was 3.0x10(-8) mol l(-1) and the calibration graph was linear over the range of 2.0x10(-7)-6.0x10(-4) mol l(-1). The relative standard deviation of H(2)O(2) was 1.1% for 2.0x10(-6) mol l(-1) (N=11). Glucose was indirectly determined through measuring the H(2)O(2) generated by the oxidation of glucose in the presence of glucose oxidase at pH 7.6. The present method provides a source for H(2)O(2), which, in turn, coupled with the luminol-KIO(4)-H(2)O(2) CL reaction system. The CL was linearly correlated with glucose concentration of 0.6-110 mug ml(-1). The relative standard deviation was 2.1% for 10 mug ml(-1) (N=11). Detection limit of glucose was 0.08 mug ml(-1). Ascorbic acid was also indirectly determined by the suppression of luminol-KIO(4)-H(2)O(2) CL system. The calibration curve was linear over the range of 1.0x10(-7)-1.0x10(-5) mol l(-1) of ascorbic acid. The relative standard deviation was 1.0% for 8.0x10(-7) mol l(-1) (N=11). Detection limit of ascorbic acid was 6.0x10(-8) mol l(-1). These proposed methods have been applied to determine glucose, ascorbic acid in tablets and injection.     

Derivative spectrophotometric determination of iridium after preconcentration of its 1-(2-pyridylazo)-2-naphthol complex on microcrystalline naphthalene

Iridium is preconcentrated from the large volume of its aqueous solution using 1-(2-pyridylazo-2-naphthol) (PAN) on microcrystalline naphthalene in the pH range of 4.5-6.0. The solid mass after filtration is dissolved with 5 ml of dimethylformamide (DMF) and the metal determined by first derivative spectrophotometry. The detection limit is 20 ppb (signal to noise ratio = 2) and the calibration curve is linear over the concentration range 0.25-75.0 mug in 5 ml of the final DMF solution with a correlation coefficient of 0.9996 and relative standard deviation of +/- 1.1%. Various parameters such as the effect of pH, volume of aqueous phase, choice of solvent, reagent and naphthalene concentration, shaking time and interference of a number of metal ions on the determination of trace amount of iridium have been studied in detail to optimize the conditions for its determination in synthetic samples corresponding to various standard alloys and environmental samples.     

Flow injection electrogenerated chemiluminescence determination of vanadium and its application to environmental water sample

A selective flow injection electrogenerated chemiluminescence(CL) method for the determination of vanadium is described in this paper. It was based on the chemiluminescence reaction of luminol with vanadium(II), which was on-line electrogenerated from vanadate using a flow-through carbon electrolytic cell. Under the optimal conditions, the CL intensity was linear to the concentration of vanadium in the range of 5.0x10(-10)-1.0x10(-7) gml(-1) with a detection limit of 2x10(-10) gml(-1) vanadium. The relative standard deviation was 4% for 5.0x10(-8) gml(-1) vanadium in 11 repeated measurements. The method has been successfully applied to the determination of vanadium in environmental water samples.