Polarographic and spectrophotometric behaviour of some N-p-phenyl substituted benzamidines

1991 ◽  
Vol 56 (12) ◽  
pp. 2791-2799 ◽  
Author(s):  
Juan A. Squella ◽  
Luis J. Nuñez-Vergara ◽  
Hernan Rodríguez ◽  
Amelia Márquez ◽  
Jose M. Rodríguez-Mellado ◽  
...  
Keyword(s):  
Spectrophotometric Study ◽  
Absorption Bands ◽  
Electrochemical Parameters ◽  
Wide Ph Range ◽  
Group A ◽  
Substituent Constants ◽  
Ph Range ◽  
The Waves

Five N-p-phenyl substituted benzamidines were studied by DC and DP polarography in a wide pH range. Coulometric results show that the overall processes are four-electron reductions. Logarithmic analysis of the waves indicate that the process are irreversible. The influence of the pH on the polarographic parameters was also studied. A UV spectrophotometric study was performed in the pH range 2-13. In basic media some variations in the absorption bands were observed due to the dissociation of the amidine group. A determination of the pK values was made by deconvolution of the spectra. Correlations of both the electrochemical parameters and spectrophotometric pK values with the Hammett substituent constants were obtained.

scholarly journals Novel Coprinopsis cinerea Polyesterase That Hydrolyzes Cutin and Suberin

2009 ◽  
Vol 75 (7) ◽  
pp. 2148-2157 ◽  
Author(s):  
Hanna Kontkanen ◽  
Ann Westerholm-Parvinen ◽  
Markku Saloheimo ◽  
Michael Bailey ◽  
Marjaana Rättö ◽  
...  
Keyword(s):  
Residual Activity ◽  
Fatty Acid Esters ◽  
Coprinopsis Cinerea ◽  
Outer Bark ◽  
Metal Affinity ◽  
Wide Ph Range ◽  
Ph Range ◽  
Laboratory Fermentor ◽  
Acid Esters

ABSTRACT Three cutinase gene-like genes from the basidiomycete Coprinopsis cinerea (Coprinus cinereus) found with a similarity search were cloned and expressed in Trichoderma reesei under the control of an inducible cbh1 promoter. The selected transformants of all three polyesterase constructs showed activity with p-nitrophenylbutyrate, used as a model substrate. The most promising transformant of the cutinase CC1G_09668.1 gene construct was cultivated in a laboratory fermentor, with a production yield of 1.4 g liter−l purified protein. The expressed cutinase (CcCUT1) was purified to homogeneity by immobilized metal affinity chromatography exploiting a C-terminal His tag. The N terminus of the enzyme was found to be blocked. The molecular mass of the purified enzyme was determined to be around 18.8 kDa by mass spectrometry. CcCUT1 had higher activity on shorter (C2 to C10) fatty acid esters of p-nitrophenol than on longer ones, and it also exhibited lipase activity. CcCUT1 had optimal activity between pH 7 and 8 but retained activity over a wide pH range. The enzyme retained 80% of its activity after 20 h of incubation at 50°C, but residual activity decreased sharply at 60°C. Microscopic analyses and determination of released hydrolysis products showed that the enzyme was able to depolymerize apple cutin and birch outer bark suberin.

Nitrate Determination in Baby Food, Using the Nitrate Ion Selective Electrode

1975 ◽  
Vol 58 (5) ◽  
pp. 915-919 ◽  
Author(s):  
Sandra L Pfeiffer ◽  
Jean Smith
Keyword(s):  
Ionic Composition ◽  
Nitrate Content ◽  
Nitrate Ion ◽  
Cation Exchange Resins ◽  
Wide Ph Range ◽  
Nitrate Determination ◽  
Comparative Results ◽  
Ph Range ◽  
Exchange Resins

Abstract The nitrate electrode has been utilized in the determination of nitrate content in food products. The AOAC xylenol method was employed for comparative results. A reasonable correlation (r = 0.91) was found between the 2 methods in the analysis of 49 samples containing 30–350 ppm nitrate. At the average nitrate content (100 ppm) of these foods, the standard error was 4.3 ppm. The electrode responds directly to the ionic activity of the nitrate ion. It has a linear concentration range of 1–6000 ppm nitrate and can be used over a wide pH range. The electrode does respond to some extent to anions other than nitrate, and some interferences do occur. These interferences are easily controlled by the use of cation exchange resins. The Corning known addition (spiking) method is used on all samples to insure correct electrode response in solutions containing variable background ionic composition. The electrode has the advantage of simplicity, speed, reproducibility, and accuracy. Work time saved using the electrode as opposed to the xylenol method is about 7 hr for the analysis of 20 samples. Error, and the need for repeating analysis, is much less frequent.

Glutathione-protected silver nanoclusters for sensing trace-level Hg2+ in a wide pH range

2015 ◽  
Vol 7 (4) ◽  
pp. 1558-1562 ◽  
Author(s):  
Yaping Zhong ◽  
Chun Deng ◽  
Yu He ◽  
Yili Ge ◽  
Gongwu Song
Keyword(s):  
Fluorescence Method ◽  
Silver Nanoclusters ◽  
Trace Level ◽  
Wide Ph Range ◽  
Ag Nanoclusters ◽  
Ph Range

A fluorescence method for the determination of Hg2+ in a wide pH range and based on the Ag nanoclusters was established.

scholarly journals The interaction of morin and morin-5’-sulfonic acid with lead(II): Study of the 1:1 complex formation process in aqueous solution

2019 ◽  
Vol 42 (1) ◽  
pp. 67-72
Author(s):  
Maxim A. Lutoshkin ◽  
Boris N. Kuznetsov ◽  
Vladimir A. Levdanskiy
Keyword(s):  
Aqueous Solution ◽  
Ionic Strength ◽  
Sulfonic Acid ◽  
Computational Models ◽  
Experimental Parameters ◽  
Wide Ph Range ◽  
Ph Range ◽  
Aqueous Complexation ◽  
Complex Formation Process

Abstract This article focuses on the aqueous complexation between two flavonoids (morin and morinsulfonate) and Pb2+ at constant ionic strength I=0.5 M (NaClO4). The determination of stability constants of ML complexes were performed at wide pH range. Two obtained constants are 14.8 ± 0.1 and 15.2 ± 0.1 logarithmic units for morin and morin-5’-sulfonic acid, respectively. For estimating the thermodynamic stability of the complexes studied, the Def2-SV(P)/DFT/PBE0/SMD method has been used. Different computational models were tested to describe the data obtained. The theoretical values of logK reproduce the experimental parameters within reasonable errors.

The Determination of the Solubility of Amorphous UO2 (Sn and the Mononuclear Hydrolysis Constants of Uranium(IV) at 25° C.

1986 ◽  
Vol 84 ◽  
Author(s):  
Jordi Bruno ◽  
Ignasi Casas ◽  
Bo Lagerman ◽  
Maria Munoz
Keyword(s):  
Stability Constants ◽  
Solubility Data ◽  
Hydrolysis Constants ◽  
Reducing Conditions ◽  
Wide Ph Range ◽  
The Stability ◽  
Ph Range ◽  
Good Agreement

AbstractWe have measured the solubility 8f amorphous UO2in a wide pH range (2 to 10.5), in 0.5 M NaClO, at T=25 C. The species responsible for the solubility are U(OH) + and U'0H)h, with the stability constants lo:1,3=-1.1± 0.1 and log, 4 =- 5.4_.O. 2, respectively. No evidence for U(OH) is f6und up to pH=10.5. The same model explains satisfactorily the solubility data obtained by Parks and Pohl(5) at T=1000 C., in the pH range 1 to 10. The measured solubility of amorphous UO2 (s) in the pH_ýange 6 to 10.5, under reducing conditions, is rather high,. U(IV) =5 10 mols/l. This is in good agreement with previous data of Gayer and Leider(6) and Galkin and Stepanov(9).

scholarly journals Polypyrrole–Methyl Orange Raman pH Sensor

Polymers ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 715 ◽  
Author(s):  
Tomasz Czaja ◽  
Kamil Wójcik ◽  
Maria Grzeszczuk ◽  
Roman Szostak
Keyword(s):  
Methyl Orange ◽  
Raman Spectra ◽  
Ph Value ◽  
Ph Sensor ◽  
First Case ◽  
Relative Standard ◽  
Wide Ph Range ◽  
Analogous Model ◽  
Ph Range

An easy-to-prepare pH sensor based on electrochemically obtained polypyrrole doped with methyl orange ions is described. It enables the determination of a pH value in the 3–13 range for volumes below 1 µL. In a wide pH range, resonance and pre-resonance methyl orange Raman spectra, excited with the 514.5 nm line of an Ar+ laser, changed noticeably in function of H+ concentration. Two types of measurements were performed. In the first case, Raman spectra of the analyzed solutions were collected for samples placed on the sensor surface using a confocal microscope equipped with a 10x objective. Next, measurements were conducted for the same samples without the sensor. On the basis of these spectra, partial least-squares models were elaborated and validated. Relative standard errors of prediction for calibration, validation, and test samples were found to be in the 3.7%–3.9% range. An analogous model build using spectra registered without the sensor was characterized by slightly worse parameters.

Spectrophotometric study of the complexation equilibria of cadmium ions with 5-bromo and 5-chloro derivatives of 2-(2-pyridylazo)-5-diethylaminophenol (BrPADAP, ClPADAP)

1983 ◽  
Vol 48 (1) ◽  
pp. 52-59 ◽  
Author(s):  
Vlastimil Kubáň ◽  
Miroslav Macka
Keyword(s):  
Equilibrium Constants ◽  
Spectrophotometric Study ◽  
Graphical Analysis ◽  
Optimal Conditions ◽  
Cadmium Ions ◽  
Brij 35 ◽  
Ethanol Medium ◽  
Triton X ◽  
Derivatives Of

The composition, optical characteristics, molar absorption coefficients and equilibrium constants of the reactions of formation of the ML and ML2 complexes of both reagents with cadmium(II) ions were determined by graphical analysis and numerical interpretation of the absorbance-pH curves by the modified SQUAD-G program. Optimal conditions were proposed for the spectrophotometric determination of Cd in 10% v/v ethanol medium in the presence of 0.1% w/v Triton X-100 or 1% w/v Brij 35. BrPADAP and ClPADAP are the most sensitive spectrophotometric reagents for the determination of cadmium(II) ions (ε = 1.28-1.44 . 105 mmol-1 cm2 at 560 nm and pH 8.0-9.5) with a high colour contrast in the reaction (Δλmax ~117 nm) and a selectivity similar to that of other N-heterocyclic azodyes (PAR, PAN, etc.).

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