Indirect complexometric determination of cadmium(II) using 1,10-phenanthroline as selective masking agent

An indirect complexometric method is described for the determination of cadmium(II), 1,10-phenanthroline being used as masking agent. Cadmium(II) in a given sample solution is initially complexed with an excess of EDTA and the surplus EDTA is titrated with lead nitrate solution at pH 5.0–6.0 (hexamine), using xylenol orange as indicator. An excess of 1,10-phenanthroline is then added and the EDTA released from the Cd-EDTA complex is titrated with standard lead nitrate solution. Results are obtained for 1.5–57 mg of Cd with relative errors 0.90% and standard deviations 0.06 mg. Cu(II), Co(II), Hg(II), Ni(II), Zn(II), Pd(II), Tl(III), Au(III) and Sn(IV) interfere, but can be easily masked. The method is applied for the determination of cadmium in synthetic alloy solutions.     

Effect of complexing agent (1,10-phenanthroline) on ADP and KDP crystals

1,10-Phenanthroline (Phen) as a new additive was added into the solutions of KH₂PO₄ (KDP) and NH₄H₂PO₄ (ADP) in a small amount (∼2.5·10⁻³ M L⁻¹). The crystals were grown from the aqueous solutions of pH ∼4.5 at constant temperature by solvent evaporation technique. It leads to an increase in metastable zone width and assists the bulk growth process. The growth rate of crystals in the presence of Phen decreases considerably with an increase in impurity concentration (∼2.5·10⁻² M L⁻¹). Not much variation is observed in FTIR and XRD of pure and doped ADP/KDP. It appears that the growth promoting effect (GPE) of Phen is caused by the adsorption of the organic additive on the prism faces of ADP/KDP crystals. Higher optical transmittance is observed in the presence of the dopant. Detailed microhardness studies of ADP crystals reveal the anisotropy in the hardness behaviour. Scanning electron microscope (SEM) photographs exhibit the effectiveness of the impurity in changing the surface morphology of ADP/KDP crystals. Contrary to expectations, Phen depresses the NLO efficiency of ADP/KDP, suggesting that the molecular alignments in the presence of Phen results in cancellation effects disturbing the non-linearity.     

Preconcentration of Cd(II) and Cu(II) by solid phase extraction on cyanopropyl modified silica columns using 1,10-phenanthroline as the complexing agent

We describe the solid-phase extraction for the preconcentration and determination of Cd(II) and Cu(II) aqueous samples by inductively coupled plasma optical emission spectrometry. The preconcentration of analytes is accomplished by retention of their chelates with 1,10-phenanthroline in aqueous solution on a solid phase containing cyanopropylsilane bonded to silica gel in a column. The preconcentration factor is 80 for the cadmium ions and 120 for the copper ions with relative standard deviations of between 0.5 and 1.5%. The limits of detection (defined as “3 s” where “s” is the standard deviation of the blank determination) are 0.18 and 0.073 μg L⁻¹ for Cd(II) and Cu(II), respectively, and the corresponding limits of quantification (6 s) are 0.36 and 0.15 μg L⁻¹, respectively. As a result, a simple method was created for simultaneous preconcentration and determination of the metals in reference material and in plant sample material. Correspondence: Bożena Puzio, Institute of Chemistry, Silesian University, 40-006 Katowice, Poland     

A novel flow injection chemiluminescence determination of Cr(VI) with Dichlorotris(1,10-phenanthroline)ruthenium(II)

A selective novel reverse flow injection system with chemiluminescence detection (rFI-CL) for the determination of Cr(VI) in presence of Cr(III) with Dichlorotris (1,10-phenanthroline)ruthenium(II), (Ru(phen)₃Cl₂), is described in this work. This new method is based on the oxidation capacity of Cr(VI) in H₂SO₄ media. First, the Ruthenium(II) complex is oxidized to Ruthenium(III) complex by Cr(VI) and afterwards it is reduced to the excited state of the Ruthenium(II) complex by a sodium oxalate solution, emitting light inside the detector. The intensity of chemiluminescence (CL) is proportional to the concentration of Cr(VI) and, under optimum conditions, it can be determined over the range of 3-300 μg L⁻¹ with a detection limit of 0.9 μg L⁻¹. The RSD was 8.4% and 1.5% at 5 and 50 μg L⁻¹, respectively. For the rFI-CL method various analytical parameters were optimized: flow rate (1 mL min⁻¹), H₂SO₄ carrier concentration (20% w/V), Ru(phen)₃Cl₂ concentration (5 mM) and sodium oxalate concentration (0.1 M). The effect of Cr(III), Fe(III), Al(III), Cd(II), Zn(II), Hg(II), Pb(II), Ca(II) and Mg(II), was studied. The method is highly sensitive and selective, allowing a fast, on-line determination of Cr(VI) in the presence of Cr(III). Finally, the method was tested in four different water samples (tap, reservoir, well and mineral), with good recovery percentage.     

Sequential injection method for the direct spectrophotometric determination of bismuth in pharmaceutical products

A spectrophotometric method is reported for the determination of bismuth in pharmaceutical products using sequential injection analysis. Methylthymol blue (MTB) was used as a color forming reagent and the absorbance of the Bi(III)-MTB complex was monitored at 548 nm. The various chemical and physical variables that affected the reaction were studied. A linear calibration graph was obtained in the range 0.0-75.0 mg l⁻¹ Bi(III) at a sampling frequency of 72 h⁻¹. The reagent consumption was considerably reduced compared to conventional flow injection systems, as only 150 μl of MTB were consumed per run. The precision was very satisfactory (s_r=0.5%, at 50.0 mg l⁻¹ Bi(III), n=12) and the limit of detection, c_L, was 0.250 mg l⁻¹. The developed method was applied successfully to the analysis of various pharmaceutical products containing Bi(III). The relative errors e_r, were <1.5% in all cases and were evaluated by comparison of the obtained results with those found using atomic absorption spectrometry as the reference method.     

Spectrothermal studies of 1,10-phenanthroline complexes of Co(II), NI(II), Cu(II) and Cd(II) orotates

The 1,10-phenanthroline (phen) complexes of Co(II), Ni(II), Cu(II) and Cd(II) orotates were synthesized and characterized by elemental analysis, magnetic susceptibility, spectral methods (UV-vis and FTIR) and thermal analysis techniques (TG, DTG and DTA). The Co(II), Ni(II), Cu(II) and Cd(II) ions in diaquabis(1,10-phenanthroline)metal(II) diorotate octahedral complexes [M(H₂O)₂(phen)₂](H₂Or)₂·nH₂O (M=Co(II), n=2.25; Ni(II), n=3; Cu(II) and Cd(II), n=2) are coordinated by two aqua ligands and two moles of phen molecules as chelating ligands through their two nitrogen atoms. The monoanionic orotate behaves as a counter ion in the complexes. On the basis of the first DTG_max, the thermal stability of the hydrated complexes follows the order: Cd(II), 68°C 68°C     

Liquid-liquid extraction and spectrophotometric determination of cadmium with 1,10-phenanthroline and thymol blue

A simple and highly sensitive extraction spectrophotometric method was developed for the determination of traces of cadmium. The method is based on the preconcentrative extraction of ternary-ion-association complex of cadmium—1,10-phenanthroline-thymol blue into chloroform and subsequent determination by spectrophotometry. The ternary ion associate is stable for 20 h and cadmium content as low as 0.1 g in 90 ml of sample can be determined. The method is precise and has been applied to the determination of cadmium in sea water, solder and high purity zinc and indium materials.     

Sequential injection lab-on-valve simultaneous spectrophotometric determination of trace amounts of copper and iron

A sequential injection (SI) method in a lab-on-valve (LOV) format for simultaneous spectrophotometric determination of copper and iron has been devised. The detection chemistry is based on the complex formation of 2-(5-bromo-2-pyridylazo)-5-[N-n-propyl-N-(3-sulfopropyl)amino]aniline (5-Br-PSAA) with copper(II) and/or iron(II) at pH 4.6. Copper(II) reacts with 5-Br-PSAA to form the complex which has an absorption maximum at 580 nm but iron(III) does not react. In the presence of a reducing agent only iron(II)-5-Br-PSAA complex is formed and detected at 558 nm. Under the optimum experimental conditions, the determinable ranges are 0.1-2 mg l⁻¹ for copper and 0.1-5 mg l⁻¹ for iron, respectively, with a sampling rate of 18 h⁻¹. The limits of detection are 50 μg l⁻¹ for copper and 25 μg l⁻¹ for iron. The relative standard deviations (n = 15) are 2% for 0.5 mg l⁻¹ copper and 1.8% for 0.5 mg l⁻¹ iron when determined in standard solutions. The recoveries range between 96 and 105% when determining 0.25-2 mg l⁻¹ of copper and 0.2-5 mg l⁻¹ of iron in artificial mixtures at copper/iron ratios of 1:10 to 5:1. The proposed SI-LOV method is successfully applied to the simultaneous determination of copper and iron in multi-element standard solution and in industrial wastewater samples.     

邻二氮菲分光光度法测定盐酸氯丙嗪

在HAc-NaAc缓冲介质中,盐酸氯丙嗪(CPZ)能定量使Fe(Ⅲ)还原为Fe(Ⅱ),还原生成的Fe(Ⅱ)与邻二氮菲反应生成稳定的红色络合物,并且在一定范围内,CPZ的浓度和生成的红色络合物的吸光度呈良好的线性关系。据此,提出邻二氮菲-Fe(Ⅲ)体系测定盐酸氯丙嗪的新方法。在优化的实验条件下,盐酸氯丙嗪的质量浓度在0.040～15.00 mg/L范围内与吸光度呈现良好的线性关系,线性相关系数R=0.9995,摩尔吸光系数ε=2.8×104 L.mol-1.cm-1,检出限为0.020 mg/L。11次重复测定的相对标准偏差小于2.9%。该方法用于药物中盐酸氯丙嗪的测定,结果满意。     

Indirect spectrophotometric determination of chloride by solvent extraction as tris(1,10-phenanthroline)iron(II) thiocyanate

An indirect spectrophotometric method for the determination of small amounts of chloride in fresh waters is described. Chloride ions react with mercury(II) thiocyanate to liberate thiocyanate ions, which can be selectively extracted into nitrobenzene with tris(1,10-phenanthroline)iron(II) chelate cations. The red color (516 nm) of the organic phase measured against a reagent blank is proportional to the initial concentration of chloride ions in the aqueous phase. At least an equimolar amount of tris(1,10-phenanthroline)iron(II) chelate and a 3-fold amount of mercury(II) thiocyanate are needed; the optimal pH range is 1.5–3.5. Beer's law is obeyed over the concentration range of 0.8–5.6 10^-5 M of chloride. The color stability and the apparent sensitivity are better than those of the mercury(II) thiocyanate-iron(III) method. Large amounts of sulphate, phosphate, fluoride, carbonate, acetate, potassium, sodium, and ammonium ions had negligible or no effect ; bromide, iodide, cyanide, sulphide, and thiocyanate interfere.     

Synthesis and structure of Mn(II) and Zn(II) complexes containing 1,10-phenanthroline unit

The Mn(II) and Zn(II) complexes of N,N′-diisopropyl-1,10-phenanthroline-2,9-dimethanamine have been synthesised, and the structure of the two complexes have been studied by X-ray crystallography.     

On-line separation, simultaneous dilution and spectrophotometric determination of zinc in fertilisers with a sequential injection system and xylenol orange as complexing agent

A dialyser unit, equipped with a passive neutral membrane, was incorporated into the conduits of a sequential injection (SI) system for the on-line removal of suspended solids and simultaneous dilution of the analyte before reaction and detection of the analyte. The system was applied to the determination of zinc(II) in fertilisers. The fully automated system is able to analyse zinc at a sampling frequency of ten samples per hour at a %R.S.D. of better than 0.55. The calibration graph was linear between 10 and 50 mg l⁻¹. The detection limit was found to be 4.75 mg l⁻¹. The results obtained with the proposed SI analyser compared favourably with the standard manual flame atomic absorption spectrometric method.     

Spectrophotometric determination of iron(III) and total iron by sequential injection analysis technique

A procedure for determination of concentrations of iron(III) and total iron by sequential injection analysis is described. The method is based on the strong blue-colored complexes formed between iron(III) and tiron. The absorbance of the complexes is measured spectrophotometrically at 635 nm. Oxidation of iron(II) and masking of interfering fluoride is simultaneously done by injecting one zone of hydrogen peroxide and one of thorium(IV) between the sample and reagent zones. Concentration of iron(III) and total iron, in the range 0.002–0.026 M, in diluted samples from a pickle bath were determined. The relative standard deviation was 0.4% (n=7). The method was also used in a pilot plant of a zinc process for determination of iron(III) in the range 0.2–3.0 g l⁻¹. The sample throughput is approximately 17 samples per hour, including three repetitive determinations of each sample.     

Transformation of 2-alkoxyimidate-1,10-phenanthroline metal (Mn, Co and Ni) chlorides from bis(2-cyano-1,10-phenanthroline) metal chlorides: Syntheses, characterizations and their catalytic behavior toward ethylene oligomerization

The 2-alkoxyimidate-1,10-phenanthroline complexes of manganese, cobalt and nickel have been synthesized by the reaction of 2-cyano-1,10-phenanthroline with metal dichloride in the corresponding alcohol. The metal complexes bearing two 2-cyano-1,10-phenanthrolines were isolated in non-protonic solvent as the coordination around metal core with two ligands and two chlorides. The alkoxyimidation of nitrile linked on ligand was speeded in forming the 2-alkoxyimidate-1,10-phenanthrolinyl metal complexes. All the complexes have been characterized by FT-IR spectra and elemental analysis, and some of their structures have also been confirmed by single-crystal X-ray diffraction analysis. All the metal complexes were evaluated in the catalytic oligomerization of ethylene with some alkylaluminums as co-catalyst; in which manganese complexes were less active, cobalt complexes showed low to moderate activities, and nickel complexes gave moderate to good activities.     

Sequential injection spectrophotometric determination of zinc(II) in pharmaceuticals based on zinc(II)–PAN in non-ionic surfactant medium

A sequential injection analysis (SIA) spectrophotometric method for the determination of trace amounts of zinc(II) with 1-(2-pyridylazo)-2-naphthol (PAN) is described. The method is based on the measurement of absorbance of the zinc(II)–PAN chelate solubilized with a non-ionic surfactant, Triton X-100, no extraction procedure is required in the proposed method, yielding a pink colored complex at pH 9.5 with absorption maximum at 553 nm. The SIA parameters that affect the signal response have been optimized in order to get the better sensitivity and minimum reagent consumption. A linear relationship between the relative peak height and concentration was obtained in the concentration range of 0.1–1.0 μg ml⁻¹. The limit of detection (LOD, defined as 3σ) and limit of quantification (LOQ, defined as 10σ) were 0.02 and 0.06 μg ml⁻¹, respectively. The sample throughput about 40 samples/h was obtained. The repeatability were 1.32 and 1.24% (n = 10) for 0.1 and 0.5 μg ml⁻¹, respectively. The proposed method was successfully applied to the assay of zinc(II) in three samples of multivitamin tablets. The results were found to be in good agreement with those obtained by flame atomic absorption spectrophotometric method and with the claimed values by the manufactures. The t-test showed no significant difference at 95% confidence level.     

Saccharin complexes of zinc(II) with phenanthroline and 2,9-dimethyl-1,10-phenanthroline: synthesis and characterization

The saccharinato complexes [Zn(phen)₂(sac)(H₂O)]sac (1) and [Zn(sac)(dmp)(H₂O)](sac) (2), where phen = 1,10-phenanthroline, dmp = 2,9-dimethyl-1,10-phenanthroline, and sac =saccharinato ion/ligand, were synthesized by the reaction of [Zn(sac)₂(H₂O)₄] · 2H₂O with ligands and have been characterized by elemental analysis, IR, and ¹H NMR spectroscopies. Conductivity of complexes was measured in DMSO. Compound 1 is characterized by single crystal X-ray diffraction and compared with some isomorphous zinc-saccharinate complexes reported previously. Complex 1 crystallizes in the triclinic system, space group P 1 , with Z = 2, and consists of alternating slightly distorted octahedral [Zn(phen)₂(sac)(H₂O)]⁺ and noncoordinated saccharinate. The zinc bound aqua is hydrogen bonded to an oxygen of carbonyl in the saccharinate ligand and the SO₂ group in the saccharinate counter-ion from an adjacent molecule. Intermolecular and intramolecular hydrogen bonds and C–H ··· O and C–H ··· N short contacts lead to a 3-D network.     

Thin-layer chromatography of tris(1,10-phenanthroline)iron(II) and tris(2,2′-bipyridine)iron(II) on Sephadex G gels

Summary Gel chromatographic behaviour of tris(1, 10-phenanthroline)iron(II), tris(2,2′-bipyridine)iron(II) and tris(glycinato)cobalt(III) on Sephadex G-10 or G-25 was investigated by TLC with 0.001–1.0M NaCl as the eluent. The zone shapes and R_M values of tris(1,10-phenanthroline)iron(II) and tris(2,2′-bipyridine)iron(II) were appreciably dependent on the sample and eluent concentration, while the neutral complex, tris(glycinato) cobalt(III), exhibited the round zones with constant R_M values. The order of R_M values was found to be tris(glycinato)cobalt(III<tris(2,2∔pyridine)iron(II)<tris-(1,10-phenanthroline)iron(II) in all systems studied, although the reverse trend was expected when assuming the chromatographic behaviour of solute compounds to be controlled by the “sieving effect”. The comparison of the behaviour on Sephadex G gels with that on CM-cellulose revealed that the predominant mechanism involved is not the sieving effect, but ion-exchange and/or hydrophobic interaction.     

Sequential injection chromatographic determination of ambroxol hydrochloride and doxycycline in pharmaceutical preparations

A new separation method based on a novel reversed-phase sequential injection chromatography (SIC) technique was used for simultaneous determination of ambroxol hydrochloride and doxycycline in pharmaceutical preparations in this contribution.The coupling of short monolith with SIA system results in an implementation of separation step to until no-separation low-pressure method.A Chromolith^® Flash RP-18e, 25-4.6 mm column (Merck, Germany) and a FIAlab^® 3000 system (USA) with a six-port selection valve and 5 ml syringe were used for sequential injection chromatographic separations in our study. The mobile phase used was acetonitrile-water (20:90, v/v), pH 2.5 adjusted with 98% phosphoric acid, flow rate 0.48 ml min⁻¹, UV detection was at 213 nm.The validation parameters have shown good results: linearity of determination for both compounds including internal standard (ethylparaben) >0.999; repeatability of determination (R.S.D.) in the range 0.5-5.4% at three different concentration levels, detection limits in the range 0.5-2.0 μg ml⁻¹, and recovery from the pharmaceutical preparation in the range 99.3-99.9%. The chromatographic resolution between peak compounds was >5.0 and analysis time was <9 min under the optimal conditions. The method was found to be applicable for routine analysis of the active compounds ambroxol hydrochloride and doxycycline in various pharmaceutical preparations.     

Cyclic voltammetric study of the redox behavior of Fe(II)/Fe(III) systems forming during the oxidation of Fe(II) complexes with saccharin and with saccharin and 1,10-phenanthroline

The electrochemical redox behavior of Fe(II)/Fe(III) systems formed during the oxidation of complexes [Fe(C₇H₄NO₃S)₂(H₂O)₄] · 2H₂O (Fe-sac) and [Fe(C₇H₄NO₃S)₂(C₁₂H₈N₂] · 2H₂O (Fe-sac-phen) have been investigated using cyclic voltammetry in the aqueous medium. In the CVs one pair of well-defined cathodic and anodic peaks appear for the transfer of single electron in the Fe-sac complex. The peak potentials are much wider separated as compared with the free (uncoordinated) Fe(II)/Fe(III) system. The ΔE values demonstrate that the electrode process is irreversible. In the presence of secondary ligand, 1,10-phenanthroline (Fe-sac-phen complex), the redox behavior of iron complexes is quasireversible. The effect of pH on the redox behavior of iron system is studied in acetate buffer. Published in Russian in Elektrokhimiya, 2008, Vol. 44, No. 12, pp. 1504–1509. The text was submitted by author in English     

Reversed flow injection and sandwich sequential injection methods for the spectrophotometric determination of copper(II) with cuprizone

Two new flow methods, flow injection analysis (FIA) and sequential injection analysis (SIA), for the spectrophotometric determination of Cu(II) in water at trace levels have been developed and optimised. Both methods are based on the reaction with oxalic acid bis(cyclohexylidene hydrazide) (cuprizone) in alkaline media. The two procedures have been developed for the final aim to compare their performances and to offer new rapid heavy metals analysis tools, avoiding the use of extraction steps. A detailed study of the physico-chemical parameters affecting the systems performances has been carried out. The reversed FIA and sandwich SIA approaches offered the best sensitivity. In both cases, an extremely good linearity has been obtained within the range 0.06-4 μg ml⁻¹ (correlation coefficient r=0.9999), whereas the observed detection limits were 0.013 and 0.004 μg ml⁻¹, for FIA and SIA, respectively. Furthermore, due to the great similarity of the diffusion zones in the reaction slugs, our approach offers the opportunity to compare the two methods in analogous conditions. This SIA method, besides keeping its typical reagent saving features, offered analytical performances equivalent to those of FIA. To obtain these results, an original “stop-flow like” method was successfully employed in the SIA approach. Both methods were validated by analysis of real water samples, after copper addition, and certified reference samples of fortified and waste waters.