Simultaneous separation of sixteen positional and optical isomers of the tryptophan family by ligand-exchange micellar electrokinetic chromatography

Summary Ligand-exchange micellar electrokinetic chromatography has been used for the simultaneous separation of 16 positional and optical isomers of the tryptophan family. The Cu(II) complex with L-hydroxyproline was used as the chiral selector. Two groups of anionic surfactant, linear alkylbenzenesulfonates (LAS) and straight-chain alkyl sulfates such as sodiumn-decyl sulfate (SDeS), sodium dodecyl sulfate (SDS) and sodiumn-tetradecyl sulfate (STS), were used for simultaneous separation. The best result was obtained by use of SDS. The influence of SDS concentration and of pH on the separation was investigated. The separation behavior in the absence of the Cu(II) complex with L-hydroxyproline was also examined. Use of organic modifiers causes the resolution to decrease. Relationships between the logarithm of the octanol-water partition coefficient (logP _OW) and resolution, and between logP _OW and migration time are discussed.     

Prediction of the environmental distribution of alkyl dinitrates – Chromatographic determination of vapor pressure p0, water solubility SH2O, gas-water partition coefficient KGW (Henry’s law constant) and octanol-water partition coefficient KOW

Alkyl nitrates are complex mixtures of homologues and isomers and are part of the large NO_y pool of important atmospheric trace compounds. The knowledge of their physico-chemical parameters allows to forecast their partitioning into the environment. Water solubility, octanol-water partition coefficient, vapor pressure, and gas-water partition coefficient have been determined for 26 alkyl dinitrates by RP-HPLC and HRGC, respectively. Octanol-water partition coefficient (K_OW) and water solubility (S_{H 2 O}) were determined by C18 reversed-phase liquid chromatography using phenylalkanes as reference standards. Retention data obtained with methanol-water mixtures as eluents were extrapolated to 100% water. The vapor pressures were determined by capillary gas chromatography on a non polar stationary phase (CP-Sil 2, Chrompack). The octanol-water partition coefficients ranges from log K_OW = 1.4 for 1,2-ethyl dinitrate up to log K_OW = 5.9 for 1,2-decyl dinitrate, respectively. The experimental results are within ± 0.15 log units in agreement with calculations of log K_OW by the increment method according to Hansch and Leo. Water solubilities are in the range of 154 mol/m³ (23.1 g/L) for 1,2-ethyl dinitrate and 0.002 mol/m³ (0.5 mg/L) for 1,2-decyl dinitrate, respectively. The vapor pressures p⁰ _L ranges from 196 Pa for 1,2-ethyl dinitrate to 0.01 Pa for 1,10-decyl dinitrate (sub-cooled liquid value). The gas-water partition constants (dimensionless) or Henry’s law constants ranges from K_GW = 0.0005 (H = 1.28 Pa m³/mol) for 1,2-ethyl dinitrate to K_GW = 0.020 (H = 51.1 Pa m³/mol) for 1,2-decyl dinitrate.     

Abraham Model Correlations for Transfer of Neutral Molecules to Tetrahydrofuran and to 1,4-Dioxane,and for Transfer of Ions to Tetrahydrofuran

Data have been compiled from the published literature for the partition coefficients of solutes and vapors into anhydrous tetrahydrofuran and 1,4-dioxane. The logarithms of the water-to-ether partition coefficients, log₁₀ P, and gas-to-ether partition coefficients, log₁₀ K, were correlated with the Abraham solvation parameter model. The derived correlations described the observed log₁₀ P and log₁₀ K values for both ether solvents to within average standard deviations of 0.16 log₁₀ units or less. The log₁₀ P correlation for tetrahydrofuran was extended to include the partition of ions by inclusion of a cation-solvent and an anion-solvent term.     

Structure-Property Correlations: XV. Properties of Phenol Derivatives

Previously proposed structure-property correlation was used to estimate the properties of methyl- and chlorophenols. The calculated boiling points, octanol-water partition coefficients (logP), energies of the lowest unoccupied molecular orbital (ELUMO), and toxicities [log(1/C _{5 0})] of mono-, di-, tri-, tetra-, and pentachlorophenols, as well as boiling points of mono-, di-, tri-, tetra-, and pentamethylphenols, agree well with the experimental data.     

The role of ion pairing in the chromatographic study of propranolol analogues

Summary The partition coefficients, logP _app ^RPLC, for a series of propranolol analogues have been determined by reversed phase high performance liquid chromatography. The hydrochloride salts and free base logP _app ^RPLC show that charged and uncharged species can partition into the reversed phase. An extrathermodynamic relationship was found for logP _app ^RPLC measured in two different column stationary phases, C8 and PMOS, suggesting that the same set of compounds experience a similar trend in these elution systems. The importance of using phosphate and/or MOPS buffer is due to the fact that the latter can avoid ion-pairing partitioning, but the former does play the same role for PMOS column when the free base is considered.     

Permeation of oxygen dissolved in water through substituted polyacetylene membranes

The permeation of oxygen dissolved in water through substituted polyacetylene membranes was studied by using an oxygen electrode at 25°C. Many of the membranes (thickness about 200 μm) showed high apparent permeability coefficients P in the range 10^?9?10^?8 cm³ (STP) cm cm^?2s^?1 cmHg^?1. The resistance r of the boundary layer and the permeability P_∞, at infinite membrane thickness were determined from the dependence of P on membrane thickness. The r values of Si-containing and aliphatic polyacetylenes were usually larger than those of aromatic polyacetylenes. The P_∞, values of Si-containing and aliphatic polyacetylenes agreed closely with the permeability coefficients P_g for gaseous oxygen. In contrast, P_∞ values for aromatic polyacetylenes were larger than P_g values.     

Correlation of the Solubilizing Abilities of 1-Butyl-1-methylpiperidinium Bis(trifluoromethylsulfonyl)imide and 1-Butyl-1-methylpyrrolidinium Tetracyanoborate

Chromatographic retention data were measured for a wide range of organic solutes on 1-butyl-1-methylpyrrolidinium tetracyanoborate ([BMPyrr]⁺[B(CN)₄]^?) and 1-butyl-1-methyl-piperidinium bis(trifluoromethylsulfonyl)imide ([BMPip]⁺[Tf₂N]^?) stationary phases at 323 K and 353 K. The measured retention factors were combined with published infinite dilution activity coefficient and gas-to-water partition coefficient data to yield gas-to-anhydrous ionic liquid (IL) and water-to-anhydrous IL partition coefficients. Both sets of partition coefficients were analyzed using the Abraham model. The derived Abraham model correlations describe the observed gas-to-IL (log₁₀ K) and water-to-IL (log₁₀ P) partition coefficient data to within average standard deviations of about 0.10 and 0.15 log₁₀ units, respectively.     

Correlation of the Solubilizing Abilities of 1-Butyl-1-methyl-pyrrolidinium Tris(pentafluoroethyl)trifluorophosphate, 1-Butyl-1-methylpyrrolidinium Triflate and 1-Methoxyethyl-1-methylmorpholinium Tris(pentafluoroethyl)trifluorophosphate

Chromatographic retention data were measured for a wide range of organic solutes on 1-butyl-1-methylpyrolidinium tris(pentafluoroethyl)trifluorophosphate ([BMPyrr]⁺[FAP]^?), 1-butyl-1-methylpyrrolidinium triflate, ([BMPyrr]⁺[Trif]^?), and 1-methoxyethyl-1-methylmorpholinium tris(pentafluoroethyl)trifluorophosphate, ([MeoeMMorp]⁺[FAP]^?), stationary phases at (323, 353 and 383) K. The measured retention factors were combined with published infinite dilution activity coefficient and gas-to-water partition coefficient data to yield gas-to-anhydrous ionic liquid (IL) and water-to-anhydrous IL partition coefficients. The three sets of partition coefficients were analyzed using the Abraham model. The derived Abraham model correlations describe the observed gas-to-IL (log₁₀ K) and water-to-IL (log₁₀ P) partition coefficient data to within average standard deviations of about 0.11 and 0.15 log₁₀ units, respectively.     

Bio Availability of Polychlorinated Biphenyl Congeners in the Soil to Earthworm (L. rubellus) System

Abstract

The earthworm's (Lumbricus rubellus) uptake of polychlorinated biphenyls (PCBs) from a soil contaminated with a commercial PCB formulation (Askarel at 150 μg g^?1) and their elimination of PCBs into a low contaminated soil (15 μg g^?1) has been studied. 17 individual congeners were monitored. The uptake and the elimination rate were similar for all PCB congeners notwithstanding their different chloro-substitution pattern which suggested that bioaccumulation of PCBs in earthworms is governed by passive, possibly diffusion controlled processes. The equilibrium state in the three-phase system, soil/soil water/earthworm was reached with a half-time around 3–4 days. The soil to earthworm bioconcentration factor ranged from 4 to 20 for tetra- to octa-chlorinated biphenyls and was weakly depending on the octanol-water partition coefficient: BCF = ?(1.3?1.8) × K _OW ^(0.35?0.40).     

Nonstationary diffusion of polystyrenes through a cellophane membrane

Diffusion of five polystyrene fractions at various concentrations in toluene through cellophane membranes has been observed. The results have been used to calculate friction coefficients between solvent and solute, and between solute and membrane. The calculation requires measurement of the diffusion coefficient and the reflection coefficient of the solute, of the permeability for the solvent, of the pore volume of the membrane, and of the partition coefficient of the solute between membrane and solvent. By comparing the friction coefficient between solvent and solute in the membrane with this coefficient in free solution, the tortuosity factor and the pore diameter of the membrane can be estimated. The dependence of the friction coefficients on molecular weight M₂ of the solute is determined. For large values of M₂, the friction between solute and solvent is the determining factor. The friction coefficient between solute and solvent increases more strongly with M₂ in the membrane than in free solution owing to an entrance effect for the permeating solute at the interface.     

Quantitative structure-property relationship: XXVI. Toxicity of aliphatic carboxylic acids

The previously suggested quantitative structure-property relationship was used for predicting properties of aliphatic carboxylic acids. The boiling points, octanol-water partition factors (logP), and toxicities [log(1/IGC₅₀)] were calculated for a series of monocarboxylic, dicarboxylic, and unsaturated monocarboxylic acids. The calculated values are well consistent with the experimental data.     

Assessment of Centrifugal Partition Chromatography for Determination of Octanol-Water Partition Coefficients

Abstract

Centrifugal partition chromatography (CPC) has been assessed as a convenient automated method for the determination of octanol-water partition coefficients (K_OW) over the range of -0.5 to 2.5 log units. The stationary (V_s) and mobile phase (V_m) volumes, which are needed for the calculation of K_ow, are determined in situ by injecting four compounds with known K_ow. V3 and V_m were also determined by independent analytical means to demonstrate that this is a direct measurement of K_ow from fundamental chromatographic principles with no unexplained fitted parameters. Propagation of error shows that a single four-component calibration with duplicate injections of each unknown is sufficient to determine log K_ow with a precision of less than 0.1 log units.     

Correlation of the Solubilizing Abilities of Hexyl(trimethyl)ammonium <Emphasis Type="Italic">bis</Emphasis>((Trifluoromethyl)sulfonyl)imide, 1-Propyl-1-methylpiperidinium <Emphasis Type="Italic">bis</Emphasis>((Trifluoromethyl)sulfonyl)imide,and 1-Butyl-1-methyl-pyrrolidinium Thiocyanate

Chromatographic retention data were measured for a wide range of organic solutes on 1-butyl-1-methylpyrrolidinium thiocyanate ([BMPyrr]⁺[SCN]⁻), hexyl(trimethyl)ammonium bis((trifluoromethyl)sulfonyl)imide ([HexM₃Am]⁺[(Tf)₂N]⁻), and 1-propyl-1-methylpiperidinium bis((trifluoromethyl)sulfonyl)imide ([PMPip]⁺[(Tf)₂N]⁻) stationary phases at 323 and 353 K. The measured retention factors were combined with published infinite dilution activity coefficient and gas-to-water partition coefficient data to yield gas-to-anhydrous ionic liquid (IL) partition coefficients and water-to-anhydrous IL partition coefficients. Both sets of partition coefficients were analyzed using the Abraham model. The derived Abraham model correlations describe the observed gas-to-IL and water-to-IL partition coefficient data to within average standard deviations of 0.116 and 0.156 log₁₀ units, respectively.     

Effect of polyethyleneglycol (PEG) on gas permeabilities and permselectivities in its cellulose acetate (CA) blend membranes

The effect of polyethyleneglycol (PEG) on gas permeabilities and selectivities was investigated in a series of miscible cellulose acetate (CA) blend membranes. The permeabilities of CO₂, H₂, O₂, CH₄, N₂ were measured at temperatures from 30 to 80°C and pressures from 20 to 76 cmHg using a manometric permeation apparatus. It was determined that the blend membrane having 10 wt% PEG20000 exhibited higher permeability for CO₂ and higher permselectivity for CO₂ over N₂ and CH₄ than those of the membranes which contained 10% PEG of the molecular weight in the range 200–6000. The CA blend containing 60 wt% PEG20000 showed that its permeability coefficients of CO₂ and ideal separation factors for CO₂ over N₂ reached above 2 × 10⁻⁸ [cm³ (STP) cm/cm² s cmHg] and 22, respectively, at 70°C and 20 cmHg. Based on the data of gas permeability coefficients, time lags and characterization of the membranes, it is proposed that the apparent solubility coefficients of all CA and PEG blend membranes for CO₂ were lower than those of the CA membrane. However, almost all the blend membranes containing PEG20000 showed higher apparent diffusivity coefficients for CO₂, resulting in higher permeability coefficients of CO₂ with relation to those of the CA membrane. It is attributed to the high diffusivity selectivities of CA and PEG20000 blend membranes that their ideal separation factors for CO₂ over N₂ were higher than those of the CA membrane in the range 50–80°C, even though the ideal separation factors of almost all PEG blend membranes for CO₂ over CH₄ became lower than those of the CA membrane over nearly the full range from 30° to 80°C.     

Prediction of extraction efficiency in supported liquid membrane with a stagnant acceptor phase by means of artificial neural network

An artificial neural network model of supported liquid membrane extraction process with a stagnant acceptor phase is proposed. Triazine herbicides and phenolic compounds were used as model compounds. The model is able to predict the compound extraction efficiency within the same family based on the octanol–water partition coefficient, water solubility, molecular mass and ionisation constant of the compound. The network uses the back‐propagation algorithm for evaluating the connection strengths representing the correlations between inputs (octanol–water partition coefficients logP, acid dissociation constant pK_a, water solubility and molecular weight) and outputs (extraction efficiency in dihexyl ether and undecane as organic solvents). The model predicted results in good agreement with the experimental data and the average deviations for all the cases are found to be smaller than ±3%. Moreover, standard statistical methods were applied for exploration of relationships between studied parameters.     

Structure-permeability relationships in silicone polymers

Permeability coefficients P for He, O₂, N₂, CO₂ CH₄, C₂H₄, C₂H₆, and C₃H₈ in 12 different silicone polymer membranes were determined at 35.0°C and pressures up to 9 atm. Values of P for CO₂, CH₄, and C₃H₈ were also determined at 10.0 and 55.0°C. In addition, mean diffusion coefficients D and solubility coefficients S were obtained for CO₂, CH₄, and C₃H₈ in 6 silicone polymers at 10.0, 35.0, and 55.0°C. Substitution of increasingly bulkier functional groups in the side and backbone chains of silicone polymers results in a significant decrease in P for a given penetrant gas. This is due mainly to a decrease in D , whereas S decreases to a much lesser extent. Backbone substitutions appear to have a somewhat lesser effect in depressing P than equivalent side-chain substitutions. The selectivity of a silicone membrane for a gas A relative to a gas B, i.e., the permeability ratio P (A)/P (B), may increase or decrease as a result of such substitutions, but only if the substituted groups are sufficiently bulky. The selectivity of the more highly permeable silicone membranes is controlled by the ratio S (A)/S (B), whereas the selectivity of the less permeable membranes depends on both the ratios D (A)/D (B) and S(A)/S(B). The permeability as well as the selectivity of one silicone membrane toward CO₂ were significantly enhanced by the substitution of a fluorine-containing side group that increased the solubility of CO₂ in that polymer.