scholarly journals Ion Association of Some 2:2 Electrolytes in Water at 25 °C. III. A New Interpretation of Experimental Results and the Determination of Formation Constants of Inner-sphere Ion-pairs

1981 ◽  
Vol 54 (8) ◽  
pp. 2286-2289 ◽  
Author(s):  
Haruhiko Yokoyama ◽  
Hideo Yamatera
Keyword(s):  
Ion Pairs ◽  
Ion Association ◽  
Formation Constants ◽  
Experimental Results ◽  
Inner Sphere ◽  
New Interpretation

scholarly journals Mefenamic Acid Selective Membranes Sensor and Its Application to pharmaceutical Analysis

2016 ◽  
Vol 13 (4) ◽  
pp. 829-837
Author(s):  
Baghdad Science Journal
Keyword(s):  
Mefenamic Acid ◽  
Limit Of Detection ◽  
Ion Pairs ◽  
Pharmaceutical Preparations ◽  
Correlation Coefficients ◽  
Ion Association ◽  
Pvc Membrane ◽  
Selective Determination ◽  
Ph Range

PVC membrane sensor for the selective determination of Mefenamic acid (MFA) was constructed. The sensor is based on ion association of MFA with Dodecaphospho molybdic acid (PMA) and Dodeca–Tungstophosphoric acid(PTA) as ion pairs. Nitro benzene (NB) and di-butyl phthalate (DBPH) were used as plasticizing agents in PVC matrix membranes. The specification of sensor based on PMA showed a linear response of a concentration range 1.0 × 10–2 –1.0 × 10–5 M, Nernstian slopes of 17.1-18.86 mV/ decade, detection limit of 7 × 10-5 -9.5 × 10 -7M, pH range 3 – 8 , with correlation coefficients lying between 0.9992 and 0.9976, respectively. By using the ionphore based on PTA gives a concentration range of 1.0 × 10–4 –1.0 × 10–5 M, Nernstian slope of 17.18-18.4 mV/ decade, limit of detection 8.0 × 10–6-9.3 × 10-5M,pH range 3 – 8 and correlation coefficients range between 0.9984 and 0.9891, respectively. The measurement interferences in the presence of Li+, Na+, Mg2+ Ca2+, Fe3+and Al3+ were studied using separate and match potential methods for selectivity coefficient determination. The method was applied for the determination of Mefenamic Acid in pharmaceutical preparations

scholarly journals Spectrophotometric and theoretical studies on the determination of etilefrine hydrochloride in pharmaceutical formulations and biological samples

2017 ◽  
Vol 16 (10) ◽  
pp. 2487-2500
Author(s):  
Ahmed Mohamed El Defrawy ◽  
Amr Lotfy Saber
Keyword(s):  
Methyl Orange ◽  
Correlation Coefficient ◽  
Density Functional ◽  
Ion Pairs ◽  
Ion Association ◽  
Pharmaceutical Formulations ◽  
Ion Pair ◽  
Bromocresol Green ◽  
Geometrical Parameters

Purpose: To develop a simple and cost effective spectrophotometric method for the determination of etilefrine hydrochloride (ET) in pharmaceutical formulations and human plasma.Methods: The method is based on extraction of ET into chloroform as ion-pair  complexes with bromocresol green (BCG) and methyl orange (MO) in acidic medium. The interaction of ET with BCG and MO reagents were investigated using  B3LYP/6-31G(d) level of theory. The geometrical parameters of the interacting species and the ion pairs formed were characterized based on their frontier  molecular orbitals, atomic charges, electrostatic potential map, as well as NBO analysis.Results: The colored species exhibited absorption maxima at 410 and 479 nm for the two systems in universal buffer of pH range (3.0 - 3.5), with molar absorptivity of 2.4 × 104 and 1.7 × 104 Lmol-1cm-1, for BCG and MO methods, respectively. The methods demonstrated good linearity with correlation coefficient ranging from  0.9987 – 0.9991 in the concentration ranges 0.5 – 16 and 2.0 – 18 μgmL-1 for BCG and MO methods, respectively. The composition ratio of the ion-association complexes was 1:1 in all cases as established by Job’s method. Sandell,s  sensitivity, correlation coefficient, detection and quantification limits were also calculated. Molecular descriptors were obtained based on optimized structures of the molecules under investigation, by applying the B3LYP/6-31G(d) method, and used to interpret the mode of interaction between these molecules to form the investigated ion pairs.Conclusion: The proposed methods make use of simple reagents, which a basic  analytical laboratory can afford. No interference was observed from common  pharmaceutical excipients and additives. ETMO ion pair has a larger interaction energy (higher stability) than ET-BCG ion pair as inferred from their interaction energies.Keywords: Density functional theory, Etilefrine hydrochloride, Ion pair complex, Spectrophotometry, Bromocresol green, Methyl orange, Geometric analysis

Determination of Charge Coefficient of Piezoelectric Films Using a Combined Finite Element Model and Dynamic Loading Technique

2020 ◽  
Vol 835 ◽  
pp. 229-242
Author(s):  
Oboso P. Bernard ◽  
Nagih M. Shaalan ◽  
Mohab Hossam ◽  
Mohsen A. Hassan
Keyword(s):  
Finite Element ◽  
Dynamic Loading ◽  
Material Properties ◽  
Accurate Determination ◽  
Substrate Material ◽  
Experimental Results ◽  
Piezoelectric Composite ◽  
Piezoelectric Film ◽  
Piezoelectric Charge

Accurate determination of piezoelectric properties such as piezoelectric charge coefficients (d33) is an essential step in the design process of sensors and actuators using piezoelectric effect. In this study, a cost-effective and accurate method based on dynamic loading technique was proposed to determine the piezoelectric charge coefficient d33. Finite element analysis (FEA) model was developed in order to estimate d33 and validate the obtained values with experimental results. The experiment was conducted on a piezoelectric disc with a known d33 value. The effect of measuring boundary conditions, substrate material properties and specimen geometry on measured d33 value were conducted. The experimental results reveal that the determined d33 coefficient by this technique is accurate as it falls within the manufactures tolerance specifications of PZT-5A piezoelectric film d33. Further, obtained simulation results on fibre reinforced and particle reinforced piezoelectric composite were found to be similar to those that have been obtained using more advanced techniques. FE-results showed that the measured d33 coefficients depend on measuring boundary condition, piezoelectric film thickness, and substrate material properties. This method was proved to be suitable for determination of d33 coefficient effectively for piezoelectric samples of any arbitrary geometry without compromising on the accuracy of measured d33.

scholarly journals A parametric prediction of the Young’s modulus of polymers enhanced with ΜWCNTs

2018 ◽  
Vol 233 ◽  
pp. 00025
Author(s):  
P.V. Polydoropoulou ◽  
K.I. Tserpes ◽  
Sp.G. Pantelakis ◽  
Ch.V. Katsiropoulos
Keyword(s):  
Young’S Modulus ◽  
Elastic Properties ◽  
Young's Modulus ◽  
Experimental Results ◽  
Scale Model ◽  
Fe Model ◽  
Multi Scale ◽  
Unit Cells ◽  
Random Dispersion

In this work a multi-scale model simulating the effect of the dispersion, the waviness as well as the agglomerations of MWCNTs on the Young’s modulus of a polymer enhanced with 0.4% MWCNTs (v/v) has been developed. Representative Unit Cells (RUCs) have been employed for the determination of the homogenized elastic properties of the MWCNT/polymer. The elastic properties computed by the RUCs were assigned to the Finite Element (FE) model of a tension specimen which was used to predict the Young’s modulus of the enhanced material. Furthermore, a comparison with experimental results obtained by tensile testing according to ASTM 638 has been made. The results show a remarkable decrease of the Young’s modulus for the polymer enhanced with aligned MWCNTs due to the increase of the CNT agglomerations. On the other hand, slight differences on the Young’s modulus have been observed for the material enhanced with randomly-oriented MWCNTs by the increase of the MWCNTs agglomerations, which might be attributed to the low concentration of the MWCNTs into the polymer. Moreover, the increase of the MWCNTs waviness led to a significant decrease of the Young’s modulus of the polymer enhanced with aligned MWCNTs. The experimental results in terms of the Young’s modulus are predicted well by assuming a random dispersion of MWCNTs into the polymer.

A Technique for the Laboratory Determination of Recirculation in Single Needle Dialysis

1993 ◽  
Vol 16 (2) ◽  
pp. 63-70 ◽  
Author(s):  
N.A. Hoenich ◽  
P.T. Smirthwaite ◽  
C. Woffindin ◽  
P. Lancaster ◽  
T.H. Frost ◽  
...  
Keyword(s):  
Experimental Data ◽  
Flow Rate ◽  
Experimental Results ◽  
New Technique ◽  
Treatment Efficiency ◽  
Single Lumen ◽  
Theoretical Predictions ◽  
Lumen Catheter ◽  
A New Technique

Recirculation is an important factor in single needle dialysis and, if high, can compromise treatment efficiency. To provide information regarding recirculation characteristics of access devices used in single needle dialysis, we have developed a new technique to characterise recirculation and have used this to measure the recirculation of a Terumo 15G fistula needle and a VasCath SC2300 single lumen catheter. The experimentally obtained results agreed well with those established clinically (8.5 ± 2.4% and 18.4 ± 3.4%). The experimental results have also demonstrated a dependence on access type, pump speeds and fistula flow rate. A comparison of experimental data with theoretical predictions showed that the latter exceeded those measured with the largest contribution being due to the experimental fistula.

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