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Burnaby Munson - One of the best experts on this subject based on the ideXlab platform.
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effects of mobile phase additives solution ph Ionization Constant and analyte concentration on the sensitivities and electrospray Ionization mass spectra of nucleoside antiviral agents
Analytical Chemistry, 1999Co-Authors: Amin Kamel, Phyllis R. Brown, Burnaby MunsonAbstract:The effects of various mobile-phase additives, solution pH, pKa, and analyte concentration on electrospray Ionization mass spectra of a series of purine and pyrimidine nucleoside antiviral agents were studied in both positive and negative ion modes. The use of 1% acetic acid resulted in good HPLC separation and the greatest sensitivity for [M + H]+ ions. In the negative ion mode, 50 mM ammonium hydroxide gave the greatest sensitivity for [M − H]- ions. The sensitivities as [M + H]+ ions were significantly larger than the sensitivities as [M − H]- ions for purine antiviral agents. Vidarabine monophosphate and pyrimidine antiviral agents, however, showed comparable or greater sensitivities as [M − H]- ions. The sensitivity as [M + H]+ showed no systematic variation with pH; however, the sensitivity as [M − H]- did increase with increasing pH. At Constant pH, the ion intensity of the protonated species increased with increasing pKa. At higher analyte concentrations, dimer (M2H+) and trimer (M3H+) ions were o...
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effects of mobile phase additives solution ph Ionization Constant and analyte concentration on the sensitivities and electrospray Ionization mass spectra of nucleoside antiviral agents
Analytical Chemistry, 1999Co-Authors: Amin Kamel, Phyllis R. Brown, Burnaby MunsonAbstract:The effects of various mobile-phase additives, solution pH, pKa, and analyte concentration on electrospray Ionization mass spectra of a series of purine and pyrimidine nucleoside antiviral agents were studied in both positive and negative ion models. The use of 1% acetic acid resulted in good HPLC separation and the greatest sensitivity for [M + H]+ ions. In the negative ion mode, 50 mM ammonium hydroxide gave the greatest sensitivity for [M - H]- ions. The sensitivities as [M + H]+ ions were significantly larger than the sensitivities as [M - H]- ions for purine antiviral agents. Vidarabine monophosphate and pyrimidine antiviral agents, however, showed comparable or greater sensitivities as [M - H]- ions. The sensitivity as [M + H]+ showed no systematic variation with pH; however, the sensitivity as [M - H]- did increase with increasing pH. At Constant pH, the ion intensity of the protonated species increased with increasing pKa. At higher analyte concentrations, dimer (M2H+) and trimer (M3H+) ions were observed. [M + Na]+ adducts were the dominant ions with 0.5 mM sodium salts for these compounds. The spectra of the more basic purine antiviral agents showed no [M + NH4]+ adduct ions, but [M + NH4]+ ions were the major peaks in the spectra of the less basic pyrimidine antiviral agents with ammonium salts. The ammonium adduct ion was formed preferentially when the proton affinity of the analyte was close to that of NH3. Abundant [M + OAc]- ions were observed for all of the antiviral agents except vidarabine monophosphate from solutions with added HOAc, NaOAc, and NH4OAc. The utility of mobile phases containing 1% HOAc or 50 mM NH4OH was demonstrated for chromatographic separations.
Serguei N Lvov - One of the best experts on this subject based on the ideXlab platform.
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the Ionization Constant of water over wide ranges of temperature and density
Journal of Physical and Chemical Reference Data, 2006Co-Authors: A V Bandura, Serguei N LvovAbstract:A semitheoretical approach for the Ionization Constant of water, KW, is used to fit the available experimental data over wide ranges of density and temperature. Statistical thermodynamics is employed to formulate a number of contributions to the standard state chemical potential of the ionic hydration process. A sorption model is developed for calculating the inner-shell term, which accounts for the ion–water interactions in the immediate ion vicinity. A new analytical expression is derived using the Bragg–Williams approximation that reproduces the dependence of a mean ion solvation number on the solvent chemical potential. The proposed model was found to be correct at the zero-density limit. The final formulation has a simple analytical form, includes seven adjustable parameters, and provides good fitting of the collected KW data, within experimental uncertainties, for a temperature range of 0–800 °C and densities of 0–1.2 g cm−3.
Amin Kamel - One of the best experts on this subject based on the ideXlab platform.
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effects of mobile phase additives solution ph Ionization Constant and analyte concentration on the sensitivities and electrospray Ionization mass spectra of nucleoside antiviral agents
Analytical Chemistry, 1999Co-Authors: Amin Kamel, Phyllis R. Brown, Burnaby MunsonAbstract:The effects of various mobile-phase additives, solution pH, pKa, and analyte concentration on electrospray Ionization mass spectra of a series of purine and pyrimidine nucleoside antiviral agents were studied in both positive and negative ion modes. The use of 1% acetic acid resulted in good HPLC separation and the greatest sensitivity for [M + H]+ ions. In the negative ion mode, 50 mM ammonium hydroxide gave the greatest sensitivity for [M − H]- ions. The sensitivities as [M + H]+ ions were significantly larger than the sensitivities as [M − H]- ions for purine antiviral agents. Vidarabine monophosphate and pyrimidine antiviral agents, however, showed comparable or greater sensitivities as [M − H]- ions. The sensitivity as [M + H]+ showed no systematic variation with pH; however, the sensitivity as [M − H]- did increase with increasing pH. At Constant pH, the ion intensity of the protonated species increased with increasing pKa. At higher analyte concentrations, dimer (M2H+) and trimer (M3H+) ions were o...
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effects of mobile phase additives solution ph Ionization Constant and analyte concentration on the sensitivities and electrospray Ionization mass spectra of nucleoside antiviral agents
Analytical Chemistry, 1999Co-Authors: Amin Kamel, Phyllis R. Brown, Burnaby MunsonAbstract:The effects of various mobile-phase additives, solution pH, pKa, and analyte concentration on electrospray Ionization mass spectra of a series of purine and pyrimidine nucleoside antiviral agents were studied in both positive and negative ion models. The use of 1% acetic acid resulted in good HPLC separation and the greatest sensitivity for [M + H]+ ions. In the negative ion mode, 50 mM ammonium hydroxide gave the greatest sensitivity for [M - H]- ions. The sensitivities as [M + H]+ ions were significantly larger than the sensitivities as [M - H]- ions for purine antiviral agents. Vidarabine monophosphate and pyrimidine antiviral agents, however, showed comparable or greater sensitivities as [M - H]- ions. The sensitivity as [M + H]+ showed no systematic variation with pH; however, the sensitivity as [M - H]- did increase with increasing pH. At Constant pH, the ion intensity of the protonated species increased with increasing pKa. At higher analyte concentrations, dimer (M2H+) and trimer (M3H+) ions were observed. [M + Na]+ adducts were the dominant ions with 0.5 mM sodium salts for these compounds. The spectra of the more basic purine antiviral agents showed no [M + NH4]+ adduct ions, but [M + NH4]+ ions were the major peaks in the spectra of the less basic pyrimidine antiviral agents with ammonium salts. The ammonium adduct ion was formed preferentially when the proton affinity of the analyte was close to that of NH3. Abundant [M + OAc]- ions were observed for all of the antiviral agents except vidarabine monophosphate from solutions with added HOAc, NaOAc, and NH4OAc. The utility of mobile phases containing 1% HOAc or 50 mM NH4OH was demonstrated for chromatographic separations.
L. M. Korkodinova - One of the best experts on this subject based on the ideXlab platform.
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quantum chemical parameters for studying the structure Ionization Constant relationship of n substituted mono di halo h anthranilic acids and their amides and hydrazides
Pharmaceutical Chemistry Journal, 2016Co-Authors: K. V. Andryukov, L. M. KorkodinovaAbstract:Ionization Constants (pKa and pKb) of N-substituted mono(di)halo(H)anthranilic acids and their amides and hydrazides were studied as functions of their quantum-chemical parameters. The predicted pKa and pKb values calculated for 10 new compounds of this series were confirmed experimentally. An analysis of the Ionization Constants predicted using the proposed equations showed them to be advantageous over other computer programs.
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Quantum-Chemical Parameters for Studying the Structure – Ionization-Constant Relationship of N-Substituted Mono(Di)Halo(H)Anthranilic Acids and Their Amides and Hydrazides
Pharmaceutical Chemistry Journal, 2016Co-Authors: K. V. Andryukov, L. M. KorkodinovaAbstract:Ionization Constants (pK_a and pK_b) of N -substituted mono(di)halo(H)anthranilic acids and their amides and hydrazides were studied as functions of their quantum-chemical parameters. The predicted pK_a and pK_b values calculated for 10 new compounds of this series were confirmed experimentally. An analysis of the Ionization Constants predicted using the proposed equations showed them to be advantageous over other computer programs.
A V Bandura - One of the best experts on this subject based on the ideXlab platform.
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the Ionization Constant of water over wide ranges of temperature and density
Journal of Physical and Chemical Reference Data, 2006Co-Authors: A V Bandura, Serguei N LvovAbstract:A semitheoretical approach for the Ionization Constant of water, KW, is used to fit the available experimental data over wide ranges of density and temperature. Statistical thermodynamics is employed to formulate a number of contributions to the standard state chemical potential of the ionic hydration process. A sorption model is developed for calculating the inner-shell term, which accounts for the ion–water interactions in the immediate ion vicinity. A new analytical expression is derived using the Bragg–Williams approximation that reproduces the dependence of a mean ion solvation number on the solvent chemical potential. The proposed model was found to be correct at the zero-density limit. The final formulation has a simple analytical form, includes seven adjustable parameters, and provides good fitting of the collected KW data, within experimental uncertainties, for a temperature range of 0–800 °C and densities of 0–1.2 g cm−3.
