Conductimetric Analysis Research Articles

Hydrolysis of phosphate diester catalyzed by new mononuclear copper(II) complexes containing selenium ligands

AbstractThree new copper(II) mononuclear complexes containing different organoselenium groups (1–3) were synthesized and characterized by the following techniques: elemental analysis, IR and UV‐Vis spectroscopies, electrochemical and conductimetric analysis, and mass spectrometry. Three new complexes, with substituents made in the para position of the aromatic portion of the N,N‐bis(2‐(phenylselanyl)ethyl)amine ligand: p‐OCH3 (1), p‐CH3 (2), and p‐Cl (3), were synthetized to compare with the already published complex (4), with no substituents. The ligand coordinates to the copper(II) center in a tridentate way with Se, N, Se as donor atoms. The hydrolytic activity in phosphate diester cleavage of the complexes was investigated using 2,4‐BDNPP as substrate. The modifications in the ligand are reflected in the difference between the catalytic and activation parameters, where the kcat values follow the order: 4 > 2 > 3 > 1.

Synthesis, structure and properties of new triiron(III) complexes: Phosphodiester cleavage and antioxidant activity

This paper describes the synthesis, structural and spectroscopic characterizations of two new trinuclear iron(III) complexes: [Fe3(LS)(μ –OH)2(μ -OAc)2]ClO4 (CS) and [Fe3(LSe)(μ –OH)2(μ -OAc)2]ClO4 (CSe) with two new phenol-based ligands containing chalcogen atoms (S or Se) in pendant arms. Both iron complexes were characterized using the following techniques: X-ray crystallography, elemental analysis, IR, Mossbauer and UV–vis spectroscopies, conductimetric analysis and mass spectrometry. The crystal structures of the complexes reveal that their coordination center is formed by three linearly arranged iron atoms, joined by μ -hydroxo, μ -phenoxo and μ -acetato bridges. The hydrolytic activity in the phosphate diester cleavage of CSe and CS was investigated using 2,4-BDNPP as a substrate, and applying the Michaelis-Menten approach, giving the kinetic parameters (CSe/CS): kcat (s−1) = 3.81 × 10-3/2.32 × 10-3 and a catalytic efficiency of E = kcat/ KM, (L/mol s−1) = 1.83/3.18. The complexes and ligands also showed antioxidant activity.

Synthesis and Characterization of Novel Copper(II)-Sunitinib Complex: Molecular Docking, DFT Studies, Hirshfeld Analysis and Cytotoxicity Studies

The main goal of this work was to report the synthesis, characterization, and cytotoxicity study of a novel copper(II)-sunitinib complex, CuSun. It has been synthesized and characterized in solid state and in solution by different methods (such as DFT, FTIR, Raman, UV-vis, EPR, NMR, etc.). The solid-state molecular structure of trichlorosunitinibcopper(II), where sunitinib: N-[2-(diethylamino)ethyl]-5-[(Z)-(5-fluoro-2-oxo-1H-indol-3-ylidene)methyl]-2,4-dimethyl-1H-pyrrole-3-carboxamide, for short Cu(Sun)Cl3, was determined by X-ray diffraction. It crystallizes in the triclinic space group P-1 with a = 7.9061(5) Å, b = 12.412(1) Å, c = 13.7005(8) Å, α = 105.021(6)°, β = 106.744(5)°, γ = 91.749(5)°, and Z = 2 molecules per unit cell. Also, we have found π-π interactions and classic and non-classic H-bonds in the crystal structure by using Hirshfeld surface analysis. In the speciation studies, the complex has dissociated in protonated sunitinib and chlorocomplex of copper(II), according to 1HNMR, EPR, UV-vis and conductimetric analysis. Molecular docking of the complex in both, ATP binding site and allosteric site of VEGFR2 have shown no improvement in comparison to the free ligand. Besides, cytotoxicity assay on HepG2 cell line shows similar activity for complex and ligand in the range between 1–25 μM supporting the data obtained from studies in solution.

Cu(ii) complexes with tridentate sulfur and selenium ligands: catecholase and hydrolysis activity

Two new copper(ii) mononuclear complexes (CSe and CS) were synthesized and characterized by the following techniques: X-ray crystallography, elemental analysis, IR, EPR and UV-vis spectroscopies, conductimetric analysis and mass spectrometry.

934-P: Continuous, Quantitative, Selective, Nonenzymatic Glucose Monitoring Using Conductimetric Analysis

Commercially available continuous glucose monitors (CGMs) typically use electrochemical sensing methods and depend on the activity of enzymes, which is subject to drift with time. Newly developed optical CGMs also suffer from drift due to the photobleaching of the fluorescent dyes. Accordingly, existing CGMs must be calibrated over periods of hours to days. Here we developed a new molecule that can be used to sense glucose concentration through conductivity sensing. The new recognition molecule binds glucose with a suitable affinity (Kd = 1 mM) and selectivity, and hosts negative charges in physiological conditions after binding with glucose. The glucose binding and charge change alters the charge spices which contribute to the conductivity of solution. Glucose concentration therefore determines the conductivity of solution. We use a conductimetric method based on low voltage AC (∼20 mV) impedance spectroscopy which offers the promise of long-term stability. Current conductimetric sensors shall be interpreted with selective permeable membrane systems and would be used to monitor sampled fluid soon. This sensor does not need expensive enzyme and fluorescent dyes, and the preparation of the novel molecule is easy and low cost. The sensing strategy only uses low voltage power, and thus is more stable than enzymatic and optical methods, providing the possibility of less or no calibration. Our current conductimetric sensors are compatible with the well-developed high frequency AC microchip technology, which makes it lower-powered and easy to be miniaturized. Disclosure B. Wang: None. S. Pennathur: Board Member; Self; Laxmi Therapeutic Devices. Consultant; Self; Alveo Technologies. K. Chou: None. Funding American Diabetes Association (1-17-VSN-18 to S.P.)

Polymer nanoparticles: adsorption and desorption of the weedkiller Tebuthiuron turned to green chemistry

The herbicide Tebuthiuron is a major responsible for controlling and combating weeds in sugarcane crops, but its use poses serious environmental risks. In order to reduce the amount of product used, a study of herbicide anchoring in nanospheres and controlled release was performed, observing factors such as conductivity and pH variation. The results of conductimetric titrations and UV analysis in the visible region showed the efficiency of the chitosan nanospheres in the controlled release process of the anchored herbicide.

Catalytic promiscuity of mononuclear copper(II) complexes in mild conditions: Catechol and cyclohexane oxidations

Two copper(II) mononuclear complexes were synthesized and investigated as promiscuous oxidative catalysts: [Cu(pymimi)Cl2]: [(2-(pyridyl-2-yl)ethyl)((1-methylimidazol-2-yl)methyl)imine](bischlorido)copper(II), C1, and [Cu(pymima)Cl2]: [(2-(pyridyl-2-yl)ethyl)((1-methylimidazol-2-yl)methyl)amine] (bischlorido)copper(II), C2. Both complexes were characterized by the following techniques: X-ray crystallography, decomposition point, elemental analysis, IR, UV–Vis and EPR spectroscopies, conductimetric analysis and electrochemistry. DFT calculations at the B3LYP level were carried out to corroborate structural, vibrational and spin Hamiltonian parameters (gx, gy and gz). TDDFT electronic spectra were calculated at CAMB3LYP level. Cyclohexane peroxidation promoted by C1 and C2 yielded the following overall conversions/turnover numbers: 48%/531s−1 and 46%/508s−1, respectively. Both complexes also catalyze the conversion of 3,5-di-tert-butylcatechol (3,5-DTBC) to 3,5-di-tert-butylquinone (3,5-DTBQ) with turnover numbers of 6.0×10−2s−1 for C1 and 11.0×10−2s−1 for C2. Complexes C1 and C2 can be classified as substrate promiscuous catalysts due to their ability to promote the oxidation of two different substrates, in the presence of distinct oxidants (O2, for catechol and H2O2 for cyclohexane).

A series of mononuclear Co(III) complexes using tridentate N,O-donor ligands: Chemical properties and cytotoxicity activity

Continuing our interest in tridentate ligands to develop new prototypes of cobalt-based metallodrugs for combating cancer, modifications in the backbone of HL1, [(2-hydroxybenzyl)(2-(pyridil-2-yl)ethyl]amine) were proposed in order to modulate the redox potential of new Co(III) complexes. Three ligands with electron withdrawing groups were synthesized: HL2: [(2-hydroxy-5-nitrobenzyl)(2-(pyridil-2-yl)ethyl]amine); HL3: [(2-hydroxybenzyl)(2-(pyridil-2-yl)ethyl]imine) and HL4: [(2-hydroxy-5-nitrobenzyl)(2-(pyridil-2-yl)ethyl]imine). They were used to obtain the respective mononuclear complexes 2, 3 and 4, which are discussed compared to the previous reported complex 1 (obtained from HL1). The new complexes were characterized and studied by several techniques including X-ray crystallography, elemental and conductimetric analysis, IR, UV–vis and 1H NMR spectroscopies, and electrochemistry. The substitutions of the group in the para position of the phenol ( HL1 and HL2) and the imine instead of the amine ( HL3 and HL4), promote anodic shifts in the complexes reduction potentials. The influence of these substitutions in the biological activities of the Co(III) complexes against the murine melanoma cell line ( B16F10) was also evaluated. Little effect was observed on cellular viability decrease for all free ligands, however the coordination to Co(III) enhances their activities in the following range: 1 > 4 ≈ 2 > 3. The data suggest that no straight correlation can be addressed between the reduction potential of the Co(III) center and the cell viability.

발효유제품에서 박테리오파지의 특성, 검출과 제어

This study was to review the classification, detection and control of bacteriophage in fermented dairy products. Bacteriophage has lytic and/or lysogenic life cycles. Epidemiologically speaking, detected major phages are c2, 936 and p335. Among them p335 has been the largest concern in dairy industry. Traditionally, various analytical technologies, such as spot, starter activity, indicator test, ATP measurement and conductimetric analysis, have been used for the phage detection. In recent years, advanced methods such as flow cytometric method, petrifilm, enzyme linked immunosorbent assay (ELISA) and multiflex PCR diagnostic kit have been deveoloped. The phage contamination has been controlled by using heat, high-pressure treatment, and the combinations of heat and pressure, and/or chemical. Also some starter cultures with phage-resistant character have been developed to minimize the concentration of phages in dairy product. Bacteriophage inhibition media such as calcium medium was also mentioned. To prevent the contamination of bacteriophage in dairy industry, further researches on the detection and control of phage, and phage resistant starters are necessary in the future.

Production of selective membranes using plasma deposited nanochanneled thin films

The hydrolization of thin films obtained by tetraethoxysilane plasma polymerization results in the formation of a nanochanneled silicone like structure that could be useful for the production of selective membranes. Therefore, the aim of this work is to test the permeation properties of hydrolyzed thin films. The films were tested for: 1) permeation of polar organic compounds and/or water in gaseous phase and 2) permeation of salt in liquid phase. The efficiency of permeation was tested using a quartz crystal microbalance (QCM) technique in gas phase and conductimetric analysis (CA) in liquid phase. The substrates used were: silicon for characterization of the deposited films, piezoelectric quartz crystals for tests of selective membranes and cellophane paper for tests of permeation. QCM analysis showed that the nanochannels allow the adsorption and/or permeation of polar organic compounds, such as acetone and 2-propanol, and water. CA showed that the films allow salt permeation after an inhibition time needed for hydrolysis of the organic radicals within the film. Due to their characteristics, the films can be used for grains protection against microorganism proliferation during storage without preventing germination.

Preparation and characterization of carboxymethylchitosan

Chitosan was reacted with monochloroacetic acid at room temperature for different reaction times (3h, 5h, 7h and 10h) and employing two chitosan/monochloroacetic acid molar ratios (1:4.3 or 1:8.6). The carboxymethylation of chitosan was confirmed by ¹H NMR and 13C NMR spectroscopy. The carboxymethylchitosans had average degrees of substitution ranging from 0.52 to 1.44 as determined by potentiometric and conductimetric analysis. The occurrence of N,O-carboxymethylation was also observed in all cases.

Diagramme polythermique du système H2O-(NH4)2HPO4-(NH4)2SO4

The polythermal diagram of the ternary system H 2 O-(NH 4 ) 2 HPO 4 -(NH 4 ) 2 SO 4 has been completed with two isotherms obtained at -15°C and 40°C by conductimetric analysis. One eutectic and one transitional transformation have been observed at -26°C and 6°C respectively.

Studies on the Characterization of Several Iridium– and Rhodium–clay Catalysts and Their Activity in Imine Hydrogenation

Iridium– and rhodium–clay catalysts were prepared by immobilizing the complexes [Ir(μ-Cl)(COD)]2 [1]+4PPh3, [Ir(COD)(PPh3)2]BF4 [2], [Ir(COD)(PPh3)2]PF6 [3], and [Rh(COD)(PPh3)2]BF4 [4] in montmorillonite K-10 (MK-10), sodium bentonite (Na+-MM), and lithium hectorite (Li+-Hect). Other analogous supports were prepared after thermal and acidic modifications to montmorillonite K-10. For example, MK-10 was calcined at 500°C (MK-10-500) and treated with nitric acid (H+HNO3-MK-10). The supports were characterized using XRD, BET surface area, FTIR, and acidity titration to confirm the properties of smectite–clay materials. The characterization of the immobilized iridium– and rhodium–clays was studied using XRD, FTIR, and conductimetric analyses. From these results, we found that the complexes are adsorbed mainly on the external surface of MK-10 and Li+-Hect. However, the immobilization of the organometallic complexes on Na+-MM is intercalated mainly by the ion-exchange process. Hydrogenation of the aldimine N-benzylidene aniline was studied with the iridium– and rhodium–clay catalytic systems. The aim of our study was to determine how the immobilized system influences the catalytic process, taking into account the metal, the counterion, and the acidity and composition of the support. In some catalytic systems the catalyst was reused for a significant number of consecutive runs. The catalyst 2–MK-10, for example, was reused in consecutive hydrogenations and showed high activity (>97% conversion) for at least 13 runs. The loss of catalytic activity as a consequence of the relative stability of the metallic intermediate species to air is also discussed.

THERMOGRAVIMETRIC AND SPECTROSCOPIC STUDIES ON CADMIUM COMPLEXES WITH TWO SALICYLIDENE THIOPHENOL SCHIFF BASES

New cadmium complexes of the salicylidene-2-amino-thiophenol (I) and 3-methoxysalicylidene-2amino-thiophenol (II) Schiff bases have been prepared and characterized by elemental analyses, IR, 1 H-NMR spectra, conductimetric and thermogravimetric analyses. The results suggested that the Schiff bases are bivalent anions with tridentate ONS donors derived from the phenolic oxygen, azomethine nitrogen and thiophenolic sulphur. The formulae are found to be [ML·H2O] and [ML2] for the 1:1 and 1:2 non-electrolytic complexes, respectively. The thermal decomposition of the complexes follows first order kinetics and the thermodynamic parameters of the decomposition are reported.

Conductimetric analysis of the interaction of Cu(II) ions and a humic-like natural polyelectrolyte (Laurel, Laurus nobilis) mixture

The influence of the ligand and metal ion concentrations on the conductimetric behavior of humic-like laurel extract–Cu(II) mixtures are analyzed by conductimetric titrations. The results obtained show that the extracts can be considered as polyelectrolytic molecules in the presence of heavy cations, forming complexes whose stability (related to the slope of a conductimetric excess function versus added Cu(II) plots) is low when compared to stronger ligands such as humic acids. The influence of ligand concentration and degree of neutralization is discussed.

Determination of Differential Carbon Dioxide Concentration by Conductimetric Analysis

AbstractThere are many applications in such disciplines as agronomy, plant physiology, and ecology where it is necessary to measure the difference in atmospheric CO2 concentration [CO2] between two points. This is commonly done with an infrared gas analyzer, but such instruments are expensive, representing a substantial and sometimes prohibitive share of the cost of CO2— related research. The goal of this project was to explore a simple inexpensive alternative, in which the difference in [CO2] between two air streams is determined by bubbling the air through cells containing deionized water while measuring the ratio of their conductivities with a half‐bridge measurement of electrode pairs suspended in each cell. The underlying principles are presented, and it is shown that (i) differential [CO2] is directly proportional to the conductivity ratio minus its inverse and (ii) the coefficient of proportionality is equal to the mean [CO2] of the two air streams. A system was designed and constructed to test these principles, and the results confirmed them. Dynamic response was characterized, and shown to be proportional to Q/V, where Q is the air flow rate and V is the water‐filled volume of the cell. Differential resolution was found to be in the range of 0.4 to 0.8 μmol mol−1, but better resolution is theoretically possible. Differential measurement of [CO2] by conductimetry shows considerable promise, particularly considering the straightforward nature of the relationship and the relatively low cost of the required components.

Influence de la formulation d'une emulsion multiple cosmétique sur la libération des actifs encapsulés

SynopsisStable multiple emulsions, which contain skin moisturizing factors, including glycolic acid in the internal aqueous phase, have been formulated. Drug incorporation and storage at 4 °C and 50 °C for 30 days do not modify macroscopic and microscopic aspects. The nature of the release mechanism for the active ingredients has been studied in different dilution conditions. Rheological and conductimetric analyses, successively realized in isoosmotic and hypoosmotic conditions, show that the active release appears after dilution by a swelling‐breakdown phenomenon. The release velocity of the water soluble active ingredients can be modulated by a modification of some formulation parameters: it can be decreased by an increase of the lipophilic surfactant concentration, it can also be increased by a hydrophilic surfactant concentration, by osmotic pressure and by a decrease of the internal globule size.

Conductimetric Analyses of Bacteriophage Infection of Two Groups of Bacteria in DL-Lactococcal Starter Cultures

Two conductimetric methods were used for simple and rapid detection of bacteriophages against the two major groups of bacteria in DL-lactococcal, mixed-strain starter cultures. Bacteriophages against the acid-producing bacteria Lactococcus lactis ssp. lactis and Lactococcus lactis ssp. cremoris in a starter were analyzed in a Malthus® instrument using reconstituted skim milk as the medium. The presence of phages against Lactococcus lactis ssp. lactis biovar. diacetylactis strains in a starter could be analyzed by measurement of CO2 production with an indirect conductance method in the Rabit® instrument. For both methods, the presence of phages against bacteria in a starter increased the detection time. At 30°C and .1% inoculum, a very sensitive assay was obtained that detected phages against acid-producing strains in a starter within 3 to 4h. The presence of 40 to 1000 infectious phages was sufficient for detection with a mixed-strain starter culture. Bacteriophages against CO2- producing bacteria were detected after 7 to 9h with a .1% inoculum at 30°C. Bacteriophage infection of single strains of bacteria reduced total change in conductance. For pure strains of an acid- or a CO2-producing strain, the detection limits were 1 and 100 pfu, respectively.

Analyse conductimétrique automatisée des équilibres solide-liquide

In order to study solid-liquid equilibria in multicomponent electrolyte systems, an automated conductimetric analysis device has been built and perfected. p]The principles of design and working are based on conductivity measurements in polyphased mixtures, without removing samples, either in the stirred mixture or in the decanted clear solution. Under these conditions, experimental determinations of phase transformations can be optimized and accurate results may be rapidly obtained. All the features of an isothermal section in a phase diagram may be deduced from such measurements. As an illustration, the ternary systems water-ammonium chloride-sodium chloride and water-magnesium chloride-calcium chloride have been established respectively at 15 and 25°C.

Conductimetric and spectrophotometric determination of the volatile acidity of wines by flow injection

Usual methods for the determination of the volatile acidity of wines are relatively slow, as about 40 min are necessary to perform one analysis. In this work, a method was developed which provides results in a much shorter time. About 60 analyses can be performed in 1 h. The conductimetric analysis consists of the injection of the wine sample into a de-ionized water stream which then flows past a poly(tetrafluoroethylene) membrane separator. The acetic acid diffuses through the membrane into another water stream that passes through a conductivity cell. The spectrophotometric method is similar. The acetic acid diffuses into a stream of Bromocresol Purple solution, at pH 7.0, which passes through a flow cell in a spectrophotometer set at 540 nm. For comparison, analyses were also carried out by the method of Jaulmes.