scholarly journals An Eco-Concerned Development of a Fast, Precise and Economical Spectrophotometric Assay for the Antiviral Drug Simeprevir based on Ion-Pair Formation

2021 ◽  
Vol 11 (5) ◽  
pp. 13474-13489
Keyword(s):  
Limit Of Detection ◽  
Ion Pairs ◽  
Antiviral Drug ◽  
Ion Pair ◽  
Pair Formation ◽  
Bromocresol Green ◽  
Bromocresol Purple ◽  
Acid Dyes ◽  
Ion Pair Formation ◽  
Relative Standard

Simeprevir sodium (SMV) is one of the antiviral drugs used for the treatment of virus C. The current strategy develops and validates a new eco-concerned tool for its quantification in the pure and pharmaceutical formulations. Sulfonephthalein acid dyes were used for this purpose, applying visible analyses based on ion-pair formation. A linear relation between the absorbed signal and the drug concentration is obtained up to 67.0 μg mL-1 with r2 of 0.9989-0.9999. The measurement is carried out at 410, 415, 410, and 403 nm for bromocresol green, bromoxelenol blue, bromothymol blue, and bromocresol purple, respectively, in dichloromethane as a solvent. The drug structure was confirmed utilizing different tools; mass spectrometry, FT-IR, 1H NMR, and thermal analysis. Association, formation constants, molar absorptivity, and free energy change for SMV-ion-pairs were calculated. The limit of detection reaches 50.0 ng mL-1 with a quantification limit of 180.0 ng mL-1. The recovery values are 96.44-104.39%, with a relative standard deviation 0.15-1.37%. For confirmation of the obtained results, they were statistically compared with a previously published HPLC method utilizing t- and F- tests.

Thermodynamics and mechanism of hydrophobic interaction

1977 ◽  
Vol 30 (4) ◽  
pp. 741 ◽  
Author(s):  
DG Oakenfull ◽  
DE Fenwick
Keyword(s):  
Free Energy ◽  
Volume Change ◽  
Hydrophobic Interaction ◽  
Ion Pairs ◽  
Hydrophobic Hydration ◽  
Partial Molar Volumes ◽  
Hydrocarbon Chain ◽  
Ion Pair ◽  
Pair Formation ◽  
Ion Pair Formation

.In the mixed solvent, 0.1 mole fraction ethanol-water, long-chain decyltrimethylammonium carboxylates form ion pairs. Ion-pair association constants (and hence the free energy of ion-pair formation) can be measured conductometrically. It is possible to separate the hydrophobic from the electrostatic contribution to the free energy of ion-pair formation by systematically varying the hydrocarbon chain length. We report measurements of the free energy of hydrophobic interaction (ΔG°HI) over the temperature range 278-328 K. The value of ΔG°HI becomes more negative (stronger hydrophobic interaction) with increasing temperature. The temperature coefficient of ΔG°HI was used to calculate the enthalpy (ΔH°HI) and entropy (ΔS°HI) of hydrophobic interaction. At low temperature the entropic contribution to the free energy is the larger but ΔH°HI, dominates at temperatures above c. 324 K. The volume change of hydrophobic interaction was similarly estimated from the volume change of ion-pair formation. We obtained values of apparent molar volume of the decyltrimethylammonium carboxylates (over a range of concentrations) from very precise density measurements. These could then be combined with the appropriate ion-pair association constant (from the conductance measurements) to give the partial molar volumes of the free ions and the ion pair. Hydrophobic interaction was found to be accompanied by a substantial increase in volume amounting to 10.2 ± 0.3 ml mol-1 for each pair of interacting methylene groups. Our results support the view that hydrophobic interaction occurs with a further ordering of water molecules over and above that which exists in the hydrophobic hydration layer surrounding an isolated hydrophobic molecule.

Elektronentransfer und Kontaktionen-Bildung, 42 [1,2] Cyclovoltammetrische und ESR / ENDOR-Untersuchungen der Einelektronen-Reduktion von Diphenochinonen / Electron Transfer and Contact Ion Pair Formation, 42 [1,2] Cyclovoltammetric and ESR / ENDOR Investigations of the One-Electron Reduction of Diphenoquinones

1995 ◽  
Vol 50 (11) ◽  
pp. 1699-1716
Author(s):  
Andreas John ◽  
Hans Bock
Keyword(s):  
Radical Anion ◽  
Ion Pairs ◽  
Ion Pair ◽  
Pair Formation ◽  
Coupling Constants ◽  
Semiquinone Radical ◽  
Additional Information ◽  
Ion Pair Formation ◽  
Contact Ion Pair ◽  
The Difference

Semiquinone radical anions are prototype compounds for contact ion pair formation with metal counter cations. In order to investigate the still open question whether bulky alkyl groups can sterically interfere, diphenoquinone derivatives O=C(RC=CH)2C=C(HC=CR)2C=O with R = C(CH3)3, CH(CH3)2 and CH3 have been selected and the following ESR/ENDOR results are obtained for the alkaline metal cations: The tetrakis(tert-butyl)-substituted radical anion only adds Li⊕ and Na⊕, while K⊕ forms no ion pair. The 3,3ʹ,5,5ʹ-tetra(isopropyl)diphenoquinone radical anion is accessible to all cations Me⊕, although Rb⊕ and Cs⊕ seem to be present solvent-separated in solution. The tetramethyl-substituted radical anion unfortunately polymerizes rapidly. Additional information concerns the ESR/ENDOR proof for ion triple radical cation formation [Li⊕ M•⊖Li⊕]•⊕, or the difference in the coupling constants upon Me⊕ docking at one δ⊖O=C group, suggesting that about 87% of the spin density is located in the cation-free molecular half of the diphenoquinone radical anion. Based on the wealth of ESR/ENDOR information, crystallization of the contact ion pairs and their structural characterization should be attempted.

Ion-Pair Formation of Sodium Salts of Several Oxo Anions and Cadmium Halides in Water and the Distribution of Monovalent Sulfate Ion Pairs in Nitrobenzene

2010 ◽  
Vol 55 (7) ◽  
pp. 2463-2469 ◽  
Author(s):  
Yoshihiro Kudo ◽  
Daisuke Todoroki ◽  
Naoki Horiuchi ◽  
Shoichi Katsuta ◽  
Yasuyuki Takeda
Keyword(s):  
Ion Pairs ◽  
Ion Pair ◽  
Pair Formation ◽  
Sulfate Ion ◽  
Sodium Salts ◽  
Ion Pair Formation ◽  
Oxo Anions

Anioneneinflüsse auf die Elektronenspinresonanz von Mangan(II)salzen in wäßriger Lösung

1969 ◽  
Vol 24 (4) ◽  
pp. 573-577 ◽  
Author(s):  
P. Nehmiz ◽  
M. Stockhausen
Keyword(s):  
Room Temperature ◽  
Ion Pairs ◽  
Ion Pair ◽  
Pair Formation ◽  
Line Broadening ◽  
Salt Solutions ◽  
Ion Pair Formation ◽  
Short Lifetime ◽  
Long Lifetime ◽  
The Mean

Abstract The mean esr linewidth of hfs components of aqueous mangenese salt solutions has been measured a t 9 GHz and room temperature from small to medium concentrations, also with added diamagnetic salts. In all cases the linewidth depends on the viscosity of the solutions. Further, already at very small concentrations a specific anion dependend line broadening has been observed, evidently resulting from ion pair formation. Roughly spoken, in the whole concentration range two anion families exist. Nitrate and halides show smaller line broadening, they form ion pairs with long lifetime. Sulfate, acetate and formiate show larger line broadening; they form ion pairs with short lifetime.

scholarly journals Microdetermination of Methenamine in the Presence of Formaldehyde by Solid Phase Spectrophotometry

2012 ◽  
Vol 2012 ◽  
pp. 1-5
Author(s):  
Mehdi Taghdiri ◽  
Yadollah Yamini ◽  
Ali Moloudi
Keyword(s):  
Industrial Wastewater ◽  
Solid Phase ◽  
Sample Volume ◽  
Ion Pair ◽  
Pair Formation ◽  
Bromocresol Green ◽  
Green Is ◽  
Relative Standard ◽  
Solid Phase Spectrophotometry

A sensitive spectrophotometric method for the determination of methenamine has been developed without any separation steps. Bromocresol green is adsorbed on Sephadex LH-20 gel but the sorption decreases in the presence of methenamine due to ion-pair formation between bromocresol green and methenamine in solution. This attenuation was used to the microdetermination of methenamine by measurement of absorbance of the solid phase (Sephadex LH-20 gel) in a 1.0 mm cell at 625 nm. Methenamine could be determined in the concentration range of 0.42–1.68 μg mL−1 (10-mL Sample volume) with a relative standard deviation (RSD) of 0.03% (n=4). The detection limit obtained was 50 μg L−1 for 10 mL sample volume. The method was used for determination of methenamine in industrial wastewater and a satisfactory result was obtained.

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