Simultaneous Determination of Nickel(II) and Cobalt(II) by Second-Derivative Spectrophotometry

4-(2-Pyridylazo) resorcinol, PAR, is shown to be useful for simultaneous determination of cobalt(II) and nickel(II) using second-derivative spectrophotometric method with controlled experimental parameters. This method allows the determination of 0.20-1.25 ppm of nickel(II) and 0.25-1.50 ppm of cobalt(II) in mixtures with good precision and accuracy. This method has advantages of simplicity, speed and requires no prior separations.     

Flow Injection Manifold for Simultaneous Spectrophotometric Determination of Bi (III), Pb (II)

Abstract

A FIA assembly producing a carrier with pH which can be adjusted to the desired pH value is propposed. It is based on the merging of two different solutions, one of them at constant flow-rate and the other at variable flow-rate. This manifold has been used for the simultaneous determination of Bi(III) and Pb(II) with Arsenazo III. Calibration curves are linear in the 1.0-11.0 ppm Bi (III) range at pH 0.25 and 1.0-12.1 ppm Pb (II) at pH 2.15. The effect of foreign ions is also reported.     

Spectrophotometric determination of mercury(II) and silver(I) with copper(II) and diethyldithiocarbamate in the presence of triton X-100

Procedures for the determination of mercury and silver by displacement of diethyldithiocarbamate (DDTC) from its copper complex in the presence of 1% Triton X-100, and measurement of the decrease in the Cu(DDTC)(2) absorbance, are described. The use of the surfactant avoids the need for an extraction step. Reproducibility within 1% and detection limits of 0.25 ppm Hg(II) and 0.45 ppm Ag(I) have been obtained, and linear calibration ranges up to 13 ppm Hg(II) and 15 ppm Ag(I). In the presence of 0.1M EDTA very good selectivity is achieved.     

Spectrophotometric determination of copper(II) using oximidobenzotetronic acid

Summary Oximidobenzotetronic acid (OBTA) is proposed as a sensitive spectrophotometric reagent for the estimation of 0.5–3.0 ppm of copper(II) at 427 nm in 50% dioxan at p_H 5.3–7.5. For the estimation of 2 ppm Cu(II), 1.3 ppm Ni(II), 1.3 ppm Co(II), 3.2 ppm Fe(II), 10.3 ppm Fe(III), 9.7 ppm Ce(IV), 300 ppm acetate, 160 ppm oxalate, 95 ppm tartrate, 50 ppm citrate, as well as Zn(II), Cd(II), Hg(II)) Pb(II), Mn(II), As(III) as well as (V), Th(IV), Be(II), Ce(III), La(III), V(V) and Mo(VI), even when present in large quantities, do not interfere. The interference due to 25 ppm Bi(III), 20 ppm Sb(III), 20 ppm Sn(II), 25 ppm Sn(IV) and 30 ppm W(VI) can be removed by the addition of 95 ppm tartrate ions.

---

Zusammenfassung Oximidobenzotetronsäure wurde als empfindliches Reagens zur spektrophotometrischen Bestimmung von 0,5 bis 3,0 ppm Kupfer(II) bei 427 nm in 50%iger Dioxanlösung bei p_H 5,3 bis 7,5 vorgeschlagen. Die Anwesenheit von 1,3 ppm Ni(II), 1,3 ppm Co(II), 3,2 ppm Fe(II), 10,3 ppm Fe(III), 9,7 ppm Ce(IV), 300 ppm Acetat, 160 ppm Oxalat, 95 ppm Tartrat, 50 ppm Citrat sowie die Anwesenheit auch großer Mengen Zn(II), Cd(II), Hg(II), Pb(II), Mn(II), As(III) bzw. (V), Th(IV), Be(II), Ce(III), La(III), V(V) und Mo(VI) stören die Bestimmung von 2 ppm Cu(II) nicht. Der störende Einfluß von 25 ppm Bi(III), 20 ppm Sb(III), 20 ppm Sn(II), 25 ppm Sn(IV) und 30 ppm W(VI) kann durch Zusatz von 95 ppm Tartrat beseitigt werden.

     

Cadmium(II) and zinc(II) complexes of S-confused thiaporphyrin

The synthesis of 5,10,15,20-tetraphenyl-2-thia-21-carbaporphyrin [S-confused thiaporphyrin, (SCPH)H] was optimized. The formation of the phlorin was detected, which was saturated at the meso carbon adjacent to thiophene. Phlorin converted readily to (SCPH)H in the final oxidation process. Insertion of cadmium(II) and zinc(II) into S-confused thiaporphyrin yielded (SCPH)Cd(II)Cl and (SCPH)Zn(II)Cl complexes. The macrocycle acted as a monoanionic ligand. Three nitrogen atoms and the C(21)H fragment of the inverted thiophene occupied equatorial positions. The compensation of the metal charge required the apical chloride coordination. The characteristic C(21)H resonances of the inverted thiophene ring were located at 1.71 and 1.86 ppm in the 1H NMR spectra of (SCPH)Cd(II)Cl and (SCPH)Zn(II)Cl, respectively. The proximity of the thiophene fragment to the metal ion induced direct scalar couplings between the spin-active nucleus of the metal (111/113Cd) and the adjacent 1H nucleus (J(CdH) = 8.97 Hz). The interaction of the metal ion and C(21)H also was reflected by significant changes of C(21) chemical shifts: (SCPH)Zn(II)Cl, 92.9 ppm and (SCPH)Cd(II)Cl, 88.2 ppm (free ligand (SCPH)H, 123.7 ppm). The X-ray analysis performed for (SCPH)Cd(II)Cl confirmed the side-on cadmium-thiophene interaction. The Cd...C(21) distance (2.615(7) A) exceeded the typical Cd-C bond lengths, but was much shorter than the corresponding van der Waals contact. The density functional theory (DFT) was applied to model the molecular structures of zinc(II) and cadmium(II) complexes of S-confused thiaporphyrin. Subsequent AIM analysis demonstrated that the accumulation of electron density between the metal and thiophene, which is necessary to induce these couplings, was fairly small. A bond path linked the cadmium(II) ion to the proximate C(22) carbon of the thiophene.     

Simultaneous Determination of Copper(II), Lead(II) and Zinc(II) at Bismuth Film Electrode by Multivariate Calibration

In this work, simultaneous determination of Cu(II), Pb(II) and Zn(II) ions at low concentration levels (ppb) by square wave anodic stripping voltammetry on a Bi(III) film electrode plated in situ at a glassy carbon electrode (GCE) is described. A chemometric approach was used to overcome the overlapping peaks of Cu(II) and Bi(III), the competition of the electrodeposited Cu and Bi for the surface of the GCE and the formation of Cu‐Zn intermetallic compounds. The construction of the multivariate calibration models, based on partial least squares regression, allowed the simultaneous determination of Cu (in the concentration range 8.0 to 20.1 ppb), Pb (2.0 to 30.0 ppb) and Zn (29.7 to 90.4 ppb) with most of the prediction errors obtained in the external validation set for the three models lower than 16, 11 and 26 %, respectively. Finally, this method was used for the determination of these trace metal ions in surface river water samples with satisfactory results [errors below 10, 5 and 32 % for Cu(II), Pb(II) and Zn(II), respectively].     

The Liquid-Liquid Extraction of Copper(II), Nickel(II), and Cobalt(II) with 2,2′-Pyridil-mono-(2-quinolylhydrazone)

A 1:1 synthesis of 2-quinolylhydrazine with 2,2′-pyridil yields the hydrazone 2,2′-pyridil-mono-(2-quinolylhydrazone). In either the Z or E isomeric configuration, the molecule can serve as a tridentate ligand. Equilibrium studies were carried out to determine the effects of pH and concentration of ligand and metal on the distribution of the extracted complex into methyl isobutyl ketone. Graphical analysis of the slopes of the plot of the logarithm of the distribution coefficient vs pH, log [ligand], and log [M(II)] will determine the stoichiometry and polymerization of the complex. In the extraction of Cu(II), Ni(II), and Co(II), there is a small change in log D, where D is the distribution coefficient, with pH indicating the presence of a weakly dissociated ligand. Ligand:metal (1:1) ion-paired species are extracted, each having three absorption peaks in the region 400-550 nm. While a spectrophotometrtc method for each element does not seem feasible due to simultaneous extraction and overlapping absorbances, an extractive-atomic absorption method for the analysis of 1.6 ppm of Cu(II) is presented. Excesses of 20-70 ppm Co(II), Zn(II), Cd(II), Cl⁻, NO₃⁻, and SO₄²⁻ do not interfere.     

H-point standard addition method for simultaneous determination of Fe(II), Co(II) and Cu(II) in micellar media with simultaneous addition of three analytes

H-point standard addition method, HPSAM, with simultaneous addition of three analytes is proposed for the resolution of ternary mixtures. It is a modification of the previously described H-point standard addition method that permits the resolution of three species from a unique calibration set by making the simultaneous addition of the three analytes. The method calculates the analyte concentration from spectral data at two wavelengths where the two species selected as interferents present the same absorbance relationship. These wavelength pairs are easily found, and can be selected to give the most precise results. Diethyldithiocarbomate (DDC) in a cationic micellar solution of cetyltrimethylammonium bromide (CTAB) was used for determination of Fe(II), Co(II) and Cu(II) at pH 5.50. The results showed that simultaneous determination of Fe(II), Co(II) and Cu(II) could be preformed in the range of 0.0–6.0, 0.0–8.0 and 0.0–12.0 μg ml⁻¹, respectively. The proposed method was successfully applied to the simultaneous determination of Fe(II), Co(II) and Cu(II) in several synthetic mixtures containing different concentration of Fe(II), Co(II) and Cu(II).     

Cadmium(II) and zinc(II) complexes of pyrrole-appended oxacarbaporphyrin: a side-on coordination mode of O-confused carbaporphyrin

A pyrrole adduct of 5,20-diphenyl-10,15-di(p-tolyl)-2-oxa-21-carbaporphyrin [(H,pyr)OCPH]H(2) reacted with sodium ethanolate to yield 5,20-diphenyl-10,15-di(p-tolyl)-3-ethoxy-3-(2'-pyrrol)-2-oxa-21-carbaporphyrin [(EtO,pyr)OCPH]H(2). Subsequently, "true" O-confused oxaporphyrin with a pendant pyrrole ring [(pyr)OCPH]H was formed by the addition of acid to [(EtO,pyr)OCPH]H(2), which triggered an ethanol elimination. In the course of this process, the tetrahedral-trigonal rearrangements originated at the C(3) atom. Insertion of zinc(II), cadmium(II), and nickel(II) into [(pyr)OCPH]H yielded [(pyr)OCPH]Zn(II)Cl, [(pyr)OCPH]Cd(II)Cl, and [(pyr)OCP]Ni(II). The formation of [(pyr)OCP]Ni(II) was accompanied by the C(21)H dehydrogenation step. The nickel(II) ion of [(pyr)OCP]Ni(II), coordinated to a dianionic macrocyclic ligand, is bound by three pyrrolic nitrogens and a trigonally hybridized C(21) atom of the inverted furan. The pyrrole-appended O-confused carbaporphyrin acts as a monoanionic ligand toward zinc(II) and cadmium(II) cations. Three nitrogen atoms and the C(21)H fragment of the inverted furan occupy equatorial positions. In (1)H NMR spectra, the unique inner C(21)H resonances of the inverted furan ring are located at 0.15 ppm for [(pyr)OCPH]Zn(II)Cl, and at 0.21 ppm for [(pyr)OCPH]Cd(II)Cl. The proximity of the furan fragment to the metal ion induces direct scalar couplings between the spin-active nucleus of the metal ((111/113)Cd) and the adjacent (1)H nucleus. The interaction of the metal ion and C(21)H was also reflected by significant changes in carbon chemical shifts ([(pyr)OCPH]Zn(II)Cl, 78.3 ppm; [(pyr)OCPH]Cd(II)Cl, 81.4 ppm; the free base, 101.3 ppm). The density functional theory (DFT) has been applied to model the molecular structures of zinc(II) and cadmium(II) complexes of O-confused oxaporphyrin with an appended pyrrole ring. The Cd...C(21) distance in the optimized structure exceeds the typical Cd-C bond lengths, but is much shorter than the corresponding van der Waals contact.     

Simultaneous kinetic spectrophotometric determination of Cu(II), Co(II) and Ni(II) using partial least squares (PLS) regression

A partial least squares (PLS-1) calibration model based on kinetic—spectrophotometric measurement, for the simultaneous determination of Cu(II), Ni(II) and Co(II) ions is described. The method was based on the difference in the rate of the reaction between Co(II), Ni(II) and Cu(II) ions with 1-(2-pyridylazo)2-naphthol in a pH 5.8 buffer solution and in micellar media at 25°C. The absorption kinetic profiles of the solutions were monitored by measuring the absorbance at 570 nm at 2 s intervals during the time range of 0–10 min after initiation of the reaction. The experimental calibration matrix for the partial least squares (PLS-1) model was designed with 30 samples. The cross-validation method was used for selecting the number of factors. The results showed that simultaneous determination could be performed in the range 0.1-2 μg mL⁻¹ for each cation. The proposed method was successfully applied to the simultaneous determination of Cu(II), Ni(II) and Co(II) ions in water and in synthetic alloy samples.      

Furoin thiosemicarbazone as an analytical reagent for nickel(II), palladium(II) and copper(II)

Furoin thiosemicarbazone (FTS) reacts with Ni(II), Pd(II) and Cu(II) in aqueous medium, giving yellow solutions at pH 9, 6 and 3 respectively. The complexes have absorption maxima at 360 nm for Ni(II) and Pd(II) and 355 nm for Cu(II). At these wavelengths the reagent absorbance is negligible. The molar absorptivities are 1.54 x 10(4) [Ni(FTS)(2)], 1.98 x 10(4) [Pd(FTS)(2)] and 1.45 x 10(4) 1.mole(-1).cm(-1) (CuFTS). Beer's law is valid up to 4, 5 and 3 ppm for Ni, Pd and Cu respectively. The apparent instability constant of the Ni-FTS system is found to be 6.5 x 10(-11), of the Cu-FTS system 7.1 x 10(-7) and of the Pd-FTS system 3 x 10(-12) at the recommended pH values. The effect of various ions is reported.     

Spectrophotometric and polarographic studies of pyridin-2-aldehyde guanylhydrazone-Fe(II) system

The analytical properties of iron(II)-PAG system are described. The optimal conditions for a spectrophotometric determination of iron are

shown. A determination of Fe(II) with PAG can be performed in a concentration range varying from 0.5 to 4.7 ppm of iron, the molar absorptivity is 1.3 × 10⁴ liters · mol^?1, at 380 nm and the relative error (95% confidence level) is ±0.3% for 1.9 ppm of iron.A polarographic behavior of iron(II)-PAG system has been attempted. Iron gives well-defined diffusion-controlled reduction wave with half-wave potential ?0.42 V at 8.5 pH value. The electrode process is discussed.     

1,8-dihydroxyanthraquinone-Mg(II) complex: II. Spectrophotometric study. Determination of Mg(II)

The 1,8-dihydroxyanthraquinone (1,8-DHAn) shows a colored and fluorescent reaction with the ion Mg(II) in a hydroalcoholic and ammonical medium.In the present work we have studied spectrophotometrically the 1,8-DHAn-Mg(II) complex in a hydroethanolic and ammonical, 8 × 10^?4M medium. We found that the complex shows a maximum absorbance at 510 nm, and obeys a 1:1 stoichiometry with log K of 4.08.We propose a new method for the spectrophotometric determination of Mg(II) which is valid for concentrations between 0.25 and 2.00 ppm, and yields an error of 1.32%.     

Oxygen Plask-TLC Microdetermination of Binary and Ternary Mixtures of Hg(II), Cu(II) and Cd in their Organic Compounds and Some Pharmaceutical Preparations

Abstract

Binary and ternary mixtures of the organic compounds of the title elements are decomposed either by wet digestion in the Kjeldahl flasks or through combustion in the oxygen flask using 1:1 HNO₃ soln. as absorbent and Pt gauze as sample holder. An aliquot of 15 μl of each decomposed mixture is separated on thin layer plate, using silica gel (G 60) as stationary phase and a mixture of 100 ml benzene: 80 ml acetone : 20 ml DMF as a mobile phase in normal saturation system at 25°C. The spots areas are determined, from which the individual concentrations of the cations are calculated. Parallely the spots are scratched from the plates and are eluted with water. Their concentrations are measured in the UV-region, for Hg(II) at 205 nm, for Cu(II) at 203 and for Cd at 201 nm. Concentrations are obtained from previously constructed calibration curves which are linear for Hg(II) in the range 0.0 – 0.375 ppm, for Cu(II) in the range 0.0 – 3.811 ppm and for Cd from 0.7 – 13.48 ppm.     

Spectrophotometric determination of carbon monoxide with ruthenium(II) octaethylporphyrin

A novel spectrophotometric method for the estimation of carbon monoxide at levels from 2 to 250 ppm is presented. The method is empirical and based on formation of a carbonyl complex of ruthenium(II) octaethylporphyrin and measurement of the difference in absorbance at 393.5 nm between this complex and the porphyrin reagent. Oxygen and nitrogen do not interfere and up to 300 ppm of sulphur dioxide and about 1500 ppm of carbon dioxide can be tolerated in determination of carbon monoxide at the 4 and 10 ppm levels. Hydrogen sulphide interferes and must be removed before the determination. The method has been tested over the range 2-45 ppm of carbon monoxide with 16 synthetic and 2 commercial standard air samples. The average error was +/- 3%. Application to urban-air samples and car-exhaust gases yielded acceptable results. The main disadvantages are the tedious preparation of the initial ruthenium(III)-porphyrin compound and the decomposition of the reagent in the presence of hydrazine.     

H-point standard addition method for simultaneous spectrophotometric determination of Co(II) and Ni(II) by 1-(2-pyridylazo)2-naphthol in micellar media

A very simple and selective spectrophotometric method for simultaneous determination of Co(II) and Ni(II) by 1-(2-pyridylazo) 2-naphthol (PAN), in micellar media, using H-point standard addition method (HPSAM) is described. The ligand and its metal complexes (Co(II)-PAN and Ni(II)-PAN) were made water-soluble by the neutral surfactant Triton X-100, and therefore, no extraction with organic solvents was required. Formation of both the complexes was complete within 10 min at pH 9 (adjusted by ammonia buffer). The linear range was 0.10-2.00 microg ml(-1) for Co(II) and 0.05-1.50 microg ml(-1) for Ni(II). The relative standard deviation (R.S.D.) for the simultaneous determination of 0.50 microg ml(-1) each of Co(II) and Ni(II) was 2.32 and 3.13%, respectively. Interference effects of common anions and cations were studied and the method was applied to simultaneous determination of Co(II) and Ni(II) in alloy samples. The method was compared with derivative spectrophotometric method.     

H-point standard addition method for simultaneous determination of cobalt(II) and zinc(II) ions

The H-point standard addition method (HPSAM) was applied to the simultaneous determination of zinc(II) and cobalt(II). This method is based on the difference in the absorbance of methylthymol blue complexes of Zn(II) and Co(II) at pH 6 buffered solution in different wavelength pairs. The results showed that Zn(II) and Co(II) can be determined simultaneously with concentration ratios of 20:1 and 1:7.5. Under working conditions, the proposed method was successfully applied to the simultaneous determination of zinc and cobalt in synthetic and real samples.     

Cadmium(II) and nickel(II) complexes of benziporphyrins. A study of weak intramolecular metal-arene interactions

Weak metal-arene interactions have been investigated in Zn, Cd, Hg, and Ni complexes of meso-tetraaryl m- and p-benziporphyrin (1 and 2) and of the new compound, m-benziporphodimethene (3). Compounds 1-3 incorporate the phenylene moiety into a macrocyclic structure so as to facilitate the interaction between the arene and coordinated metal ion. X-ray studies performed on Cd(II) and Ni(II) complexes show that the arene fragment approaches the ion at a distance much shorter than the sum of van der Waals radii. In chloronickel(II) m-benziporphyrin, a weak agostic bond is actually formed. In the NMR spectra of the Cd(II) and Hg(II) species, unusual (1)H-M and (13)C-M scalar couplings have been observed that are transmitted directly between the metal and the arene. DFT calculations performed for two Cd(II) species and subsequent AIM analysis show that the accumulation of electron density between the metal and arene necessary to induce these couplings is fairly small and the interaction is steric in nature. In the paramagnetic Ni(II) complexes of 1 and 3, the agostic proton of the m-phenylene exhibits large downfield (1)H NMR shifts (386 and 208 ppm at 298 K, respectively). An agostic mechanism of spin density transfer is proposed to explain these shifts as resulting from electron donation from the CH bond to the metal. In chloronickel(II) p-benziporphyrin, the inner protons of the p-phenylene have a contrastingly small shift (0.0 ppm at 298 K), indicating that in this case the agostic interaction is inefficient, in agreement with the X-ray data.     

H-point standard addition method for simultaneous determination of cobalt(II) and zinc(II) ions

The H-point standard addition method (HPSAM) was applied to the simultaneous determination of zinc(II) and cobalt(II). This method is based on the difference in the absorbance of methylthymol blue complexes of Zn(II) and Co(II) at pH 6 using different wavelength pairs. The results showed that Zn(II) and Co(II) can be determined simultaneously with concentration ratios of 20:1 and 1:7.5. Under working conditions, the proposed method was successfully applied to the simultaneous determination of zinc and cobalt in synthetic, drinking water and vitamin samples.     

Simultaneous determination of cadmium(II), lead(II) and copper(II) by using a screen-printed electrode modified with mercury nano-droplets

We are presenting a strategy for the fabrication of disposable screen-printed electrodes modified with mercury nano-droplets and capable of sensing heavy metal ions. They were prepared by coating electrodes with a mixture of multi-walled carbon nanotubes and chitosan, this followed by adsorption of mercury. The resulting sensor was characterized by cyclic voltammetry and impedance spectroscopy. Also the effects caused by adsorption of mercury were investigated. It is shown that square wave anodic stripping voltammetry enables simultaneous determination of cadmium(II), lead(II) and copper(II), for which detection limits of 12, 23 and 20 nM, respectively, are found. Relative standard deviations for ten determinations at 0.6 µM concentrations of these ions are in the range of 3.0 to 5.7%. The applicability was tested by analyzing river water and showed recoveries between 94.1 and 104.6%, thus demonstrating its utility for in-field monitoring of these heavy metal ions.