Cobalt phthalocyanine as a novel molecular recognition reagent for batch and flow injection potentiometric and spectrophotometric determination of anionic surfactants

Cobalt(II) phthalocyanine [Co(II)Pc] is used as both an ionophore and chromogen for batch and flow injection potentiometric and spectrophotometric determination of anionic surfactants (SDS), respectively. The potentiometric technique involves preparation of a polymeric membrane sensor by dispersing [Co(II)Pc] in a plasticized PVC membrane. Under batch mode of operation, the sensor displays a near-Nernstian slope of −56.5 mV decade⁻¹, wide response linear range of 7.8 × 10⁻⁴ to 8.0 × 10⁻⁷ mol L⁻¹, lower detection limit of 2.5 × 10⁻⁷ mol L⁻¹ and exhibits high selectivity for anionic surfactants in the presence of many common ions. Under hydrodynamic mode of operation (FIA), the slope of the calibration plot, limit of detection, and working linear range are −51.1 mV decade⁻¹, 5.6 × 10⁻⁷ and 1.0 × 10⁻³ to 1.0 × 10⁻⁶ mol L⁻¹, respectively. The spectrophotometric method is based on the use of [Co(II)Pc] solution in dimethylsulfoxide (DMSO) as a chromogenic reagent. The maximum absorption of the reagent at 658 nm linearly decreases with the increase of anionic surfactant over the concentration range 2-30 μg mL⁻¹. The lower limit of detection is 1 μg mL⁻¹ and high concentrations of many interfering ions are tolerated. Flow injection spectrophotometric measurements are carried out by injection of the surfactant test solution in a stream of the reagent in DMSO. The sample throughput, working range and lower detection limit are 25-30 samples h⁻¹, 4-60 and 2 μg mL⁻¹, respectively. The potentiometric and spectrophotometric techniques are applied to the batch and flow injection measurements of anionic surfactants in some commercial detergent products. The results agree fairly well with data obtained using the standard methylene blue spectrophotometric method.     

Diffusion layer titration of dipyrone in pharmaceuticals at a dual-band electrochemical cell

This paper describes the use of a thin-layered dual-band electrochemical cell operating at flow conditions to determine dipyrone (sodium salt of 1-phenil-2,3-dimethyl-4-methylaminomethanesulfonate-5-pyrazolone) by reaction with electrogenerated iodine. The electrolytic cell consisted of two closely spaced gold electrodes, the upper stream electrode serving as the generator electrode and the downstream electrode working as the collector electrode. A linear dynamic range from 2 to 15 μmol l⁻¹ dipyrone was obtained by using a sample volume of 100 μl, with a detection limit of 1.1 μmol l⁻¹. Standard deviation (S.D.) of 3.4% for 20 repetitive injections of a 40 μmol l⁻¹ dipyrone solution and sampling frequency of 90 h⁻¹ were achieved. The results obtained with the thin-layered dual-band electrochemical cell for dipyrone determination in three different pharmaceutical samples compared well with those found by iodimetry with coulometrically generated iodine.     

Quantification of N-acetylcysteine in pharmaceuticals using cobalt phthalocyanine modified graphite electrodes

Flow injection analysis (FIA) with amperometric detection was employed for the quantification of N-acetylcysteine (NAC) in pharmaceutical formulations, utilizing an ordinary pyrolytic graphite (OPG) electrode modified with cobalt phthalocyanine (CoPc). Cyclic voltammetry was used in preliminary studies to establish the best conditions for NAC analysis. In FIA-amperometric experiments the OPG-CoPc electrode exhibited sharp and reproducible current peaks over a wide linear working range (5.0 × 10⁻⁵-1.0 × 10⁻³ mol L⁻¹) in 0.1 mol L⁻¹ NaOH solution. High sensitivity (130 mA mol⁻¹ cm²) and a low detection limit (9.0 × 10⁻⁷ mol L⁻¹) were achieved using the sensor. The repeatability (R.S.D.%) for 13 successive flow injections of a solution containing 5.0 × 10⁻⁴ mol L⁻¹ NAC was 1.1%. The new procedure was applied in analyses of commercial pharmaceutical products and the results were in excellent agreement with those obtained using the official titrimetric method. The proposed amperometric method is highly suitable for quality control analyses of NAC in pharmaceuticals since it is rapid, precise and requires much less work than the recommended titrimetric method.     

Determination of diethylstilbestrol by enhancement of luminol-hydrogen peroxide-tetrasulfonated cobalt phthalocyanine chemiluminescence

The ability of diethylstilbestrol to enhance the chemiluminescence reaction of luminol-H₂O₂, catalyzed by tetrasulfonated cobalt phthalocyanine in an alkaline medium, has been exploited to develop a new flow injection chemiluminescence method for the determination of diethylstilbestrol. Under the optimum conditions, the linearity of the calibration graph for the determination of diethylstilbestrol was in the range from 1.00×10⁻⁷ to 4.00×10⁻⁶ mol/l. The assay was sensitive (the detection limit was 6.42×10⁻⁸ mol/l, S/N=3), reproducible (the relative standard deviation was 2.6%, n=11), and accurate (recovery up to 92%). The method has been successfully applied to the determination of diethylstilbestrol in the pharmaceutical formulations. Dienestrol and hexestrol were specifically alkylphenols, which are similar to diethylstilbestrol, could be detected by this method. Furthermore, the enhanced mechanism of estrogen-like compounds was also discussed in this paper.     

L-酪氨酸为指示剂四羧基钴酞菁催化瑞利散射法测定青蒿素

常温常压下,在pH 10.0的Britton-Robinson缓冲溶液中,以及8.0×10-7 mol/L四羧基钴酞菁催化作用下,L-酪氨酸与青蒿素反应,瑞利散射光谱发生变化.其288 nm处瑞利散射光降低,降低值△I(I0-I)与青蒿素浓度在0～4.6×10-5 mol/L范围内呈线性关系,相关系数r为0.9985;检出限为4.89×10-7 mol/L.方法已用于中药青蒿草中青蒿素的检测.     

CopperII phthalocyanine as an efficient and reusable catalyst for the N-arylation of nitrogen containing heterocycles

Copper phthalocyanine (Cu^IIPc) was found to be an efficient catalyst for the catalyzed N-arylation of NH heterocycles with aryl iodides and bromides under mild reaction conditions. A variety of hindered and functionalized NH heterocycles and aryl halides were successfully used as the substrates for the given catalytic reaction and were transformed in good to excellent yields.     

Electrocatalytic Oxidation and Voltammetric Determination of Hydrazine in Industrial Boiler Feed Water Using a Cobalt Phthalocyanine-modified Electrode

Abstract

A carbon paste electrode modified with cobalt phthalocyanine (CPECoPc) was developed and applied to the determination of hydrazine [N₂H₄] in industrial boiler feed water. The CPECoPc exhibited good electrocatalytical activity for hydrazine oxidation at pH 13. A linear correlation was obtained between anodic peak current (I_ap) and hydrazine concentration in the range of 1.25 × 10^?4 to 9.80 × 10^?4 mol L^?1, fit by the equation I_ap = 1.47 + 4.90 × 10⁵ [N₂H₄] with a correlation coefficient of 0.9967. A detection limit of 7.35 × 10^?5 mol L^?1 was obtained. Recovery of hydrazine from three samples ranged between 99.0% and 102.9%. The modified electrode showed no interference by cations commonly present in boiler water, such as K⁺, Na⁺, Ca²⁺, Mg²⁺, Al³⁺, Pb²⁺, and Zn²⁺. The results obtained for hydrazine in boiler water using the proposed modified electrode are in agreement with the data obtained by a standard spectrophotometric method, at the 95% confidence level.     

酞菁钴修饰碳糊电极对微量苯酚的测定

研究了苯酚在酞菁钴修饰碳糊电极上的电化学行为,提出了催化反应的机理,并以此为依据,用伏安法以酞菁钴修饰碳糊电极为工作电极测定了微量苯酚.在pH 8.7的磷酸盐缓冲溶液(PBS)中,苯酚在0.61 V(对SCE)出现一氧化峰,该峰电流与苯酚的浓度在5.0×10-7～1.0×10-4 mol/L之间呈线性关系,检出限为1.0×10-7 mol/L.此法可用于工业废水中苯酚的测定.     

Fabrication of a covalently attached multilayer film electrode containing cobalt phthalocyanine and its application as a potentiometric sensor of iodide ion

Construction of a highly stable covalently attached multilayer film electrode containing cobalt phthalocyanine was achieved by UV irradiation of ionic self-assembled multilayer films of diazo-resins (DAR) and cobalt phthalocyanine tetrasulfonic acid (CoTsPc) tetrasodium salt. The modified electrode had good potentiometric response to iodide ion. The potentiometric response was independent of the pH of the solution between pH 2.5 and 6.0, while it was dependent on the nature of the buffer media. The modified electrode had a linear dynamic range between 4.7×10⁻⁶ M and 0.1 M with a Nernstian slope of 58.8 mV per decade and a detection limit of 3.5×10⁻⁶ M in acetate buffer (0.1 M, pH 4.6). The modified electrode also exhibited a fast response, good stability and repeatability.     

偏最小二乘法—流动注射pH梯度技术用于同时测定铜和钴

以PAR作显色剂,用流动注射pH梯度技术测定多个不同pH下的吸光度,以偏最小二乘法建立校正模型并预测,对Cu~(2+)、Co~(2+)二元素进行了同时测定,其计算结果优于主成分回归及多元线性回归法。     

Direct electrochemical determination of carbaryl using a multi-walled carbon nanotube/cobalt phthalocyanine modified electrode

The electrochemical detection of carbaryl at low potentials, in order to avoid matrix interferences, is an important challenge. This study describes the development, electrochemical characterization and utilization of a glassy carbon (GC) electrode modified with multi-wall carbon nanotubes (MWCNT) plus cobalt phthalocyanine (CoPc) for the quantitative determination of carbaryl in natural waters. The surface morphology was examined by scanning electron microscopy, enhanced sensitivity was observed with respect to bare glassy carbon and electrocatalytic effects reduced the oxidation potential to +0.80 V vs. SCE in acetate buffer solution at pH 4.0. Electrochemical impedance spectroscopy was used to estimate the rate constant of the oxidation process and square-wave voltammetry to investigate the effect of electrolyte pH. Square-wave voltammetry in acetate buffer solution at pH 4.0, allowed the development of a method to determine carbaryl, without any previous step of extraction, clean-up, or derivatization, in the range of 0.33-6.61 μmol L⁻¹, with a detection limit of 5.46 ± 0.02 nmol L⁻¹ (1.09 ± 0.02 μg L⁻¹) in water. Natural water samples spiked with carbaryl and without any purification step were successfully analyzed by the standard addition method using the GC/MWCNT/CoPc film electrode.     

Lead determination at the ppb level using stopped-flow FIA

A flow-injection-based kinetic method for the determination of lead ions was developed. In this method, resazurin was reduced to resorufin by sulfide and lead ions. The method has a detection limit of 1 ppb with a relative standard deviation of 5.2% at the 20 ppb level. Interferences can be removed by prior extraction.     

Inorganic tin(II) determination by FIA with amperometric detection of its oxinate complex

A highly selective, rapid and direct amperometric method, based on the formation of a complex between tin(II) and 8-hydroxyquinoline (oxine), has been developed for the determination of trace levels of tin(II) using flow injection analysis. Tin(II) electro-oxidation was catalyzed by oxine; its oxidation peak occurred at +0.05 V vs. Ag/AgCl at a glassy carbon electrode in 0.1 mol 1⁻¹ acetate buffer (pH 6). A linear relationship was obtained between the peak current and the tin(II) concentration in the range 0.25-20 μmol 1⁻¹. The detection limit was 0.1 μmol 1⁻¹ and the relative standard deviation calculated by the injection of a 10 μmol 1⁻¹ tin(II) solution was 5% (n = 20). Optimization of several experimental parameters has been carried out and the influence of numerous cations and possible interfering molecules encountered in radiopharmaceuticals and in dental gels has been investigated. The method was applied to the determination of tin(II) in dental gels.     

流动注射分析光度法测定食品中CO(Ⅱ)

自行研制了一套流动比色装置,进行了双光束流动注射分析光度法的应用研究.基于二溴羟基苯荧光酮(DBHPF)与钴形成紫色络合物的原理,提出了一种新的流动注射微分测试技术,方法进样速度为110～120次/时,浓度在0～0.6μg/mL呈良好的线性关系.对0.3μg/mL的Co(Ⅱ)连续11次进样平行测定相对标准偏差为1.2%.用于食品中微量钴的测定,结果满意.     

A flow-injection chemiluminescence method for the determination of some estrogens by enhancement of luminol-hydrogen peroxide-tetrasulfonated manganese phthalocyanine reaction

A novel flow-injection chemiluminescence (FI-CL) method for the determination of estrogens is proposed, based upon its enhancing effect on the CL reaction of luminol with hydrogen peroxide catalyzed by tetrasulfonated manganese phthalocyanine (MnTSPc) in alkaline solution. Under the selected experimental conditions, a linear relationship was obtained between the CL intensity and the concentration of estrone in the range of 1.0 × 10⁻⁷ to 1.0 × 10⁻⁶ mol/l, estradiol in the range of 9.0 × 10⁻⁸ to 1.0 × 10⁻⁶ mol/l and estriol in the range of 3.0 × 10⁻⁷ to 2.0 × 10⁻⁶ mol/l, respectively. The detection limits were 5.1 × 10⁻⁸ mol/l for estrone, 7.2 × 10⁻⁹ mol/l for estradiol and 6.5 × 10⁻⁸ mol/l for estriol with a relative standard deviation of 2.8% for 5.0 × 10⁻⁷ mol/l estrone, 2.4% for 1.0 × 10⁻⁷ mol/l estradiol, and 3.1% for 7.0 × 10⁻⁷ mol/l estriol (n = 11). This method has been applied to the determination of estrogen in pharmaceutical injections and tap water with satisfactory results.     

Syntheses and investigation of the effects of position and nature of substituent on the spectral,electrochemical and spectroelectrochemical properties of new cobalt phthalocyanine complexes

The syntheses of new cobalt phthalocyanine (CoPc) complexes, tetra-substituted with diethylaminoethanethio at the peripheral (complex 3a) and non-peripheral (complex 3b) positions, and with benzylmercapto at the non-peripheral position (complex 5), are reported. The effects of the nature and position of substituent on the spectral, electrochemical and spectroelectrochemical properties of these complexes are investigated. Solution electrochemistry of complex 3a showed three distinctly resolved redox processes attributed to Co^IIIPc⁻²/Co^IIPc⁻² (E_½ = +0.64 V versus Ag|AgCl), Co^IIPc⁻²/Co^IPc⁻² (E_½ = −0.24 V versus Ag|AgCl) and Co^IPc⁻²/Co^IPc⁻³ (E_½ = −1.26 V versus Ag|AgCl) species. No ring oxidation was observed in complex 3a. Complex 3b showed both ring-based oxidation, attributed to Co^IIIPc⁻¹/Co^IIIPc⁻² species (E_p = +0.86 V versus Ag|AgCl), and ring-based reduction associated with Co^IPc⁻²/Co^IPc⁻³ species (E_½ = −1.46 V versus Ag|AgCl), with the normal metal-based redox processes in CoPc complexes: Co^IIIPc⁻²/Co^IIPc⁻² (E_p = +0.41 V versus Ag|AgCl) and Co^IIPc⁻²/Co^IPc⁻² (E_½ = −0.38 V versus Ag|AgCl). Solution electrochemistry of complex 5 showed the same type and number of species observed in complex 3a: Co^IIIPc⁻²/Co^IIPc⁻² (E_p = +0.59 V versus Ag|AgCl), Co^IIPc⁻²/Co^IPc⁻² (E_½ = −0.26 V versus Ag|AgCl) and Co^IPc⁻²/Co^IPc⁻³ (E_½ = −1.39 V versus Ag|AgCl) species. These processes were confirmed using spectroelectrochemistry.     

Cobalt oxide supported gold nanoparticles as a stable and readily-prepared precursor for the in situ generation of cobalt carbonyl like species

A treatment of cobalt oxide supported gold nanoparticles (Au/Co₃O₄) under syngas atmosphere effectively generated a cobalt carbonyl-like active species in the reaction vessel. The preparation of Au/Co₃O₄ was quite simple and the in situ generated cobalt species could be used as a stable and easy handling alternative for dicobalt octacarbonyl without bothersome purification prior to use. The reactions, which are sensitive to the purity of the dicobalt octacarbonyl, such as the alkoxycarbonylation of epoxides and the Pauson-Khand reaction, smoothly progressed with Au/Co₃O₄.     

Evaluation of different mediator-modified screen-printed electrodes used in a flow system as amperometric sensors for NADH

This work presents a comparative study between two different methods for the preparation of mediator-modified screen-printed electrodes, to be used as detectors in a reliable flow injection system for the determination of the nicotinamide adenine dinucleotide (NADH) coenzyme. The best strategy was selected for the final development of compact biosensors based on dehydrogenase enzymes. For the first immobilisation strategy, different redox mediators were electropolymerised onto the SPE surface. The second immobilisation strategy was carried out using polysulfone–graphite composites, which were deposited by screen-printing technology onto the screen-printed electrode (SPE) surface. Both methods achieved an effective and reliable incorporation of redox mediators to the SPE configuration. Finally, a flow system for ammonium determination was developed using a glutamate dehydrogenase (GlDH)-Meldola's Blue (MB)-polysulfone-composite film-based biosensor.

The stability of the redox mediators inside the composite films as well as the negligible fouling effect observed on the electrode surface improve the repeatability and reproducibility of the sensors, important features for continuous analysis in flow systems. Furthermore, the optimised bio/sensors, incorporated in a flow injection system, showed good sensitivities and short response times. Such a good analytical performance together with the simple and fast sensor construction are interesting characteristics to consider the polysulfone-composite films as attractive electrochemical transducer materials for the development of new dehydrogenase-based SPEs.     

Application of cobalt phthalocyanine as a nanostructured catalyst in the synthesis of biological henna‐based compounds

The present investigation describes synthesis of a good range of henna‐based compounds in the presence of novel nano cobalt phthalocyanine like molten salt (tetra‐2,3‐pyridiniumporphyrazinato cobalt tribromomethanide) [Co (TPPABr)]CBr₃ as an efficient, recyclable and thermally stable heterogeneous catalyst.