Abraham Solvation Model Research Articles

Assessing Aquatic Baseline Toxicity of Plastic-Associated Chemicals: Development and Validation of the Target Plastic Model.

We developed a Target Plastic Model (TPM) to estimate the critical plastic burden of organic toxicants in five types of plastics, namely, polydimethylsiloxane (PDMS), polyoxymethylene (POM), polyacrylate (PA), low-density polyethylene (LDPE), and polyurethane ester (PU), following the Target Lipid Model (TLM) framework. By substituting the lipid-water partition coefficient in the TLM with plastic-water partition coefficients to create TPM, we demonstrated that the biomimetic nature of these plastic phases allows for the calculation of critical plastic burdens of toxicants, similar to the notion of critical lipid burdens in TLM. Following this approach, the critical plastic burdens of baseline (n = 115), less-inert (n = 73), and reactive (n = 75) toxicants ranged from 0.17 to 51.33, 0.04 to 26.62, and 1.00 × 10-6 to 6.78 × 10-4 mmol/kg of plastic, respectively. Our study showed that PDMS, PA, POM, PE, and PU are similar to biomembranes in mimicking the passive exchange of chemicals with the water phase. Using the TPM, median lethal concentration (LC50) values for fish exposed to baseline toxicants were predicted, and the results agreed with experimental values, with RMSE ranging from 0.311 to 0.538 log unit. Similarly, for the same data set of baseline toxicants, other widely used models, including the TLM (RMSE: 0.32-0.34), ECOSAR (RMSE: 0.35), and the Abraham Solvation Model (ASM; RMSE: 0.31), demonstrated comparable agreement between experimental and predicted values. For less inert chemicals, predictions were within a factor of 5 of experimental values. Comparatively, ASM and ECOSAR showed predictions within a factor of 2 and 3, respectively. The TLM based on phospholipid had predictions within a factor of 3 and octanol within a factor of 4, indicating that the TPM's performance for less inert chemicals is comparable to these established models. Unlike these methods, the TPM requires only the knowledge of plastic bound concentration for a given plastic phase to calculate baseline toxic units, bypassing the need for extensive LC50 and plastic-water partition coefficient data, which are often limited for emerging chemicals. Taken together, the TPM can provide valuable insights into the toxicities of chemicals associated with environmental plastic phases, assisting in selecting the best polymeric phase for passive sampling and designing better passive dosing techniques for toxicity experiments.

Screening Disinfection Byproducts in Arid-Coastal Wastewater: A Workflow Using GC×GC-TOFMS, Passive Sampling, and NMF Deconvolution Algorithm.

Disinfection during tertiary municipal wastewater treatment is a necessary step to control the spread of pathogens; unfortunately, it also gives rise to numerous disinfection byproducts (DBPs), only a few of which are regulated because of the analytical challenges associated with the vast number of potential DBPs. This study utilized polydimethylsiloxane (PDMS) passive samplers, comprehensive two-dimensional gas chromatography (GC×GC) coupled with time-of-flight mass spectrometry (TOFMS), and non-negative matrix factorization (NMF) spectral deconvolution for suspect screening of DBPs in treated wastewater. PDMS samplers were deployed upstream and downstream of the chlorination unit in a municipal wastewater treatment plant located in Abu Dhabi, and their extracts were analyzed using GC×GC-TOFMS. A workflow incorporating a multi-tiered, eight-filter screening process was developed, which successfully enabled the reliable isolation of 22 candidate DBPs from thousands of peaks. The NMF spectral deconvolution improved the match factor score of unknown mass spectra to the reference mass spectra available in the NIST library by 17% and facilitated the identification of seven additional DBPs. The close match of the first-dimension retention index data and the GC×GC elution patterns of DBPs, both predicted using the Abraham solvation model, with their respective experimental counterparts-with the measured data available in the NIST WebBook and the GC×GC elution patterns being those observed for the candidate peaks-significantly enhanced the accuracy of peak assignment. Isotopic pattern analysis revealed a close correspondence for 11 DBPs with clearly visible isotopologues in reference spectra, thereby further strengthening the confidence in the peak assignment of these DBPs. Brominated analogues were prevalent among the detected DBPs, possibly due to seawater intrusion. The fate, behavior, persistence, and toxicity of tentatively identified DBPs were assessed using EPI Suite™ and the CompTox Chemicals Dashboard. This revealed their significant toxicity to aquatic organisms, including developmental, mutagenic, and endocrine-disrupting effects in certain DBPs. Some DBPs also showed activity in various CompTox bioassays, implicating them in adverse molecular pathways. Additionally, 11 DBPs demonstrated high environmental persistence and resistance to biodegradation. This combined approach offers a powerful tool for future research and environmental monitoring, enabling accurate identification and assessment of DBPs and their potential risks.

Evaluation of Thermodynamic and Kinetic Contributions to Over-Extraction of Extractables by Nonpolar Organic Solvents in Comparison to Lipids in Exhaustive and Exaggerated Extractions of Medical Devices Based on Abraham Solvation Model and Solvent–Material Interactions Using Low-Density Polyethylene as a Representative Material

The thermodynamic and kinetic contributions to the over-extraction of extractables by nonpolar organic solvents relative to biological lipids in exhaustive and exaggerated extractions of medical devices are studied based on the Abraham solvation model and solvent–material interactions, using low-density polyethylene (LDPE) as an exemplary material. The thermodynamic effect is evaluated by the partition constant of extractables between LDPE and extraction solvents, hexane and lipids, defined as the concentration in the polymer phase divided by the concentration in the solvent phase. The Abraham solvation model is used to correlate the measured LDPE-lipid partition constant (log10Pldpe/lipid) to construct the predictive model. Similar models are also derived from the thermodynamic cycle conversion, using the system constants of LDPE-water and Lipid-water partition systems. These constructed models, together with the predictive LDPE-hexane (log10Pldpe/hexane) model established from a previous study, are used to predict and compare the ranges and values of Pldpe/s (s = lipids and hexane) for the observed LDPE extractables over a wide hydrophobicity range in log10Po/w from zero to 30. The solvent-LDPE interactions are examined by the degree of swelling of LDPE by hexane (or other nonpolar solvents) and lipids, including the solvent diffusion rates into the material. These parameters allow the evaluation of kinetic effect on the over-extraction. The extent of over-extraction is compiled directly by experimental “overall” or “specific” migration data or indirectly calculated by the diffusion coefficient of extractables when extracted by hexane or lipids. It is concluded from this study that the extractables distribution between LDPE and lipids highly favors the lipid phase thermodynamically (Pldpe/lipid<1), and the values of Pldpe/lipid are always lower than those of Pldpe/hexane, thereby indicating that the thermodynamic effect is not the cause of over-extraction. It is the kinetic effect that dominantly contributes to the over-extraction, as supported by the material swelling and solvent diffusion rates. Finally, the extent of over-extraction has been established from a few folds to over a hundred-fold, and the median value is 7. Furthermore, the methods adopted and developed in this study can be invaluable tools in other disciplines such as the reliable prediction of extractables from other device materials and environmental sampling.

A new set of solute descriptors to calculate solubility of drugs in mono-solvents

A new set of solute parameters derived from a correlation model using Catalan parameters. The parameters represent the interaction of the solute with the mono-solvents at 298.15K. The computational procedure was adopted from Abraham's solvation model and the obtained results are promising. In this work, the calculated parameters were used to back-calculate the drugs solubility in various mono-solvents at different temperatures employing the van't Hoff's model as the skeleton on the derived model. The obtained mean percentage deviations (MPDs) were in the range of 3.1 to 88.5% with the overall MPD of 29.1%. (1) Derivation of a new set of solute parameters from a correlation model using Catalan parameters; (2) adoption of the calculation method of Abraham's solvation model with the skeleton of van't Hoff's equation; (3) using the achieved parameters for back-calculation of drugs solubility in various mono-solvents; (4) obtaining an overall acceptable mean percentage deviation of 29.1% from calculations.

Evaluation of fatty tissue representative solvents in extraction of medical devices for chromatographic analysis of devices’ extractables and leachables based on Abraham general solvation model

Extraction solvents used in chemical characterization (i.e., extractables and leachables testing, E&L) of fatty tissue-contacting medical devices for biocompatibility assessment per ISO 10993 have been studied by Abraham general solvation models. Chemically suitable alternative solvents to fatty tissues in solvation properties (solubility, partition, extraction, etc.) have been proposed based on Abraham's organic solvent system coefficients for water and air to condensed organic solvent phases. This evaluation is built upon the conclusion by Abraham, Acree Jr and Cometto-Muñiz that olive oil is chemically corresponding to fatty tissues. However, olive oil, if used as an extraction solvent to simulate fatty tissues, is in general not analytically expedient (realistic) per ISO 10993-18 (2020) for chromatographic analysis, and it is critical to seek alternative solvents to olive oil to perform the extraction. Although nonpolar solvents such as alkanes have been proposed and used as alternative solvents to vegetable oils, they are not equivalent to olive oil in solvation properties. Due to the practical challenge in chromatographic analysis of oil samples and the difference in migration kinetics of E&L between oil and organic solvents, the computational approach is the only realistic option to evaluate chemically alternative solvents to olive oil to simulate fatty tissue extraction. By comparing Abraham solvent system coefficients for water and air to condensed organic solvent phases distribution, a five-dimensional space distance (D) between solvents and olive oil as a reference solvent is calculated using Abraham and Martin equation to predict alternative or similar solvents to olive oil. The results of the calculation are further evaluated using E&L solubility ratio between solvents and olive oil, taking into consideration of solvent safety and physical properties. It is concluded from the study that butanone and dioxane are chemically the most suitable alternative or representative solvents to olive oil. They can be used as fatty tissue representative solvents in chemical characterization study of medical device. As Abraham solvation model is solvent system specific, not solute specific, the conclusions from this study are considered as universal.

QSPRs for Predicting Equilibrium Partitioning in Solvent–Air Systems from the Chemical Structures of Solutes and Solvents

Poly-parameter Linear Free Energy Relationships (PPLFERs) based on the Abraham solvation model are a useful tool for predicting and interpreting equilibrium partitioning of solutes in solvent systems. The focus of this work is neutral organic solutes partitioning in neutral organic liquid solvent-air systems. This is a follow-up to previous work (Brown, 2021) which developed predictive empirical correlations between solute descriptors and system parameters, allowing system parameters to be predicted from the solute descriptors of the solvent. A database of solute descriptors, and a database of system parameters supplemented by empirical predictions, form the basis for the development of new Quantitative Structure Property Relationships (QSPRs). A total of 11 QSPRs have been developed for the E, S, A, B and L solute descriptors, and the s, a, b, v, l, and c system parameters. The QSPRs were developed using a group-contribution method referred to as Iterative Fragment Selection. The method includes robust internal and external model validation and a well-defined Applicability Domain, including estimates of prediction uncertainty. System parameters can also be predicted by combining the solute descriptor QSPRs and the empirical correlations. The predictive power of PPLFERs applied using different combinations of experimental data, empirical correlations, and QSPRs are externally validated by predicting partition ratios between solvents and air. The uncertainty for predicting the log10KSA of diverse solutes in diverse solvents using only the new QSPRs and empirical correlations is estimated to be one log10 unit or less.

Evaluation of blood simulating solvents in extractables and leachables testing for chemical characterization of medical devices based on Abraham general solvation model

Extraction vehicles (simulating solvents) used in chemical characterization (i.e., extractables/leachables testing) of blood-contacting medical devices for biocompatibility assessment per ISO 10993 have been studied by Abraham general solvation models. Chemically equivalent solvents to blood in solvation properties (solubility, partition, extraction, etc.) have been proposed based on Abraham’s organic solvent system coefficients for water and air to condensed organic solvent phases. This evaluation is built upon the conclusion by Abraham, Acree Jr and Cometto-Muñiz that water saturated n-butanol (called wet n-butanol) is chemically corresponding to blood. Although wet n-butanol can be directly used to replace blood in an extraction study (such as a simulated-use extraction study per ISO 10993-18 (2020)), it can be beneficial to have alternate solvents to wet n-butanol (butan-1-ol) when chromatographic interference is practically significant. By comparing Abraham solvent system coefficients for water to condensed organic solvent phases distribution, a five-dimensional space distance (D) between solvents and reference solvent (wet n-butanol) is calculated using Abraham and Martin equation to predict equivalent or similar solvents (to wet n-butanol). It is concluded from the study that ethanol/water (60/40, V/V) and ethanol/water (50/50, V/V) are chemically equivalent or quite similar to wet n-Butanol. Other two less similar solvents are ethylene glycol and ethanol/water (70/30, V/V). Thus, n-butanol, ethanol/water (60/40, V/V) and ethanol/water (50/50, V/V) can be used as blood simulating solvents in chemical characterization study of medical device. In certain situations, ethylene glycol might be desirable as an alternate solvent, as it is not a mixture. As Abraham solvation model is general (solvent system specific, not solute specific), the conclusions from this study are considered as universal.

Solid-liquid phase equilibrium of trans-cinnamic acid, p-coumaric acid and ferulic acid in water and organic solvents: Experimental and modelling studies

The solubility of the trans isomers of cinnamic acid, p-coumaric acid and ferulic acid was measured in water and seven organic solvents (methanol, ethanol, 1-propanol, 2-propanol, 2-butanone, ethyl acetate and acetonitrile), at 298.2 K and 313.2 K, using the analytical shake-flask technique. The melting temperatures and enthalpies of the solutes were studied by differential scanning calorimetry, while solute solid structures were identified by powder and single X-ray diffraction.The NRTL-SAC model was applied to calculate the solubility of trans-cinnamic acid and trans-ferulic acid in pure solvents. For trans-p-coumaric acid, the NRTL-SAC was combined with the Reference Solvent Approach, as the solute melting properties could not be determined. The global average relative deviations (ARD) were 32% and 41%, in the correlation and prediction stages, respectively. The Abraham solvation model was also applied. The global ARD were 20% for correlation and 29% for predictions, which can be considered very satisfactory results for these semi-predictive models.

Predictions of solvation Gibbs free energies with COSMO-SAC approaches

The modelling of a detailed kinetics mechanism in the liquid phase is still not well understood, and the description of solvent effect on reaction rates remains a challenge. Green and co-workers proposed an approach to predict the kinetic constants in liquid phases, which is based on a correction of the kinetic constants in the gas phase. The correction term in Green's approach involves the solvation Gibbs free energies of the chemical species involved in the reactions. Examples of applications of the method are the kinetic modelling of the oxidation of liquid fuels or the catalytic pyrolysis of biomass. However, an accurate thermodynamic model is required to predict the solvation energies. In this work, several predictive models of solvation energies are compared to the large set of experimental data reported recently by Moine et al. [J. Phys. Chem. Ref. Data, 46, 2017] in the CompSol database. Activity coefficients and solvation Gibbs free energies were calculated with different versions of the COSMO-SAC thermodynamic model. We propose a re-optimisation of the universal parameters of these COSMO-SAC models, and extend them to CPCM cavities. It is found that these approaches are in general much more accurate than the Abraham solvation model that is usually employed in Green's approach.

Characterization of bis(fluorosulfonyl)imide based ionic liquids by gas chromatography

Infinite dilution thermodynamic properties of organic solutes dissolved in four bis(sulfonyl)imide ionic liquids namely 1-butyl-1-methylpyrrolidinium bis(fluorosulfonyl)imide, N-propyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide, 1-ethyl-1-methylimidazolium bis(fluorosulfonyl)imide and 1-methyl-1-propylpiperidinium bis(fluorosulfonyl)imide were measured in a large range of temperature using inverse gas chromatography. The characterization of ILs using the Abraham solvation model indicates that the cation has an impact on the polarizability and on the acidity of the solvent. The derived Abraham model correlations rigorously describe the experimental partition coefficient data to within 0.09 (or fewer) log units. In addition, the activity coefficient at infinite dilution of organic solutes in these ILs was predicted using the conductor-like screening model for real solvents (COSMO-RS). It was found that COSMO-RS give a reasonable representation of experimental data. Then, selectivity and capacity at infinity dilution have been determined for the separation problems (thiophene/water), (benzene/water), (acetone/water), (1-butanol/water), (acetonitrile/water) and (pyridine/water) at 323.15 K.

Solvent and temperature effects on the solubility of syringic, vanillic or veratric acids: Experimental, modeling and solid phase studies

The solubility of syringic acid, vanillic acid and veratric acid was measured in pure water and eleven organic solvents (methanol, ethanol, 1-propanol, 2-propanol, 2-butanone, ethyl acetate, acetonitrile, dimethylformamide, 1,2-propanediol, 1,3-propanediol and 1,3-butanediol), at 298.2 K and 313.2 K. Besides the solubility data, the melting temperatures and enthalpies of the solutes were determined by differential scanning calorimetry, while powder and single X-ray diffraction were used to resolve the solute solid structure, before and after the solubility studies.For modeling purposes, the NRTL-SAC model, also combined with the Reference Solvent Approach (RSA), and the Abraham solvation model were applied to describe the solid-liquid equilibria of the binary systems. A set of solvents was used to estimate the model parameters and afterwards, solubility predictions were carried out for binary systems not included in the correlation step. Better results were obtained using the Abraham solvation model with average relative deviations (ARD) of 15% for the correlation set and 26% for the predictions, which are more satisfactory than the results found with the NRTL-SAC model (33% for the correlation and 59% for the predictions) or the NRTL-SAC model combined with RSA (30% for the correlation and 59% for the predictions).

Development of QSARs for parameterizing Physiology Based ToxicoKinetic models

A Quantitative Structure Activity Relationship (QSAR) model was developed in order to predict physicochemical and biochemical properties of industrial chemicals of various groups. This model was based on the solvation equation, originally proposed by Abraham. In this work Abraham's solvation model got parameterized using artificial intelligence techniques such as artificial neural networks (ANNs) for the prediction of partitioning into kidney, heart, adipose, liver, muscle, brain and lung for the estimation of the bodyweight-normalized maximal metabolic velocity (Vmax) and the Michaelis – Menten constant (Km). Model parameterization using ANNs was compared to the use of non-linear regression (NLR) for organic chemicals. The coupling of ANNs with Abraham's solvation equation resulted in a model with strong predictive power (R2 up to 0.95) for both partitioning and biokinetic parameters. The proposed model outperformed other QSAR models found in the literature, especially with regard to the estimation and prediction of key biokinetic parameters such as Km. The results show that the physicochemical descriptors used in the model successfully describe the complex interactions of the micro-processes governing chemical distribution and metabolism in human tissues. Moreover, ANNs provide a flexible mathematical framework to capture the non-linear biochemical and biological interactions compared to less flexible regression techniques.

Microemulsion electrokinetic chromatography as a suitable tool for lipophilicity determination of acidic, neutral, and basic compounds.

In the present work, several MEEKC systems are studied to assess their suitability for lipophilicity determination of acidic, neutral, and basic compounds. Thus, several microemulsion compositions over a wide range of pH values (from 2.0 to 12.0), containing heptane, 1-butanol and different types and amounts of surfactant (SDS or sodium cholate: from 1.3 to 3.3%) are characterized using Abraham's solvation model. The addition of acetonitrile (up to 10%) is also studied, since it increases the resolution of the technique for the most lipophilic compounds. The system coefficients obtained are very similar to those of the 1-octanol/water, used as the reference lipophilicity index, allowing simple and linear correlations between the 1-octanol/water partition values (log Po/w ) and MEEKC mass distribution ratios (log kMEEKC ). Variations in the microemulsion composition (aqueous buffer, surfactant, concentration of ACN) did not significantly affect the similarity of the MEEKC systems to log Po/w partition.

Effect of sorbate-β-cyclodextrin complexation on the retention of aniline derivatives on a graphite-like adsorbent under HPLC conditions

The effect complexation with molecules of β-cyclodextrins (β-CDs) has on the thermodynamic characteristics of adsorption and the selectivity of the separation of aniline and its derivatives on surfaces of a Hypercarb graphite-like material from a water-methanol eluent is studied. The effect the nature of the functional groups present in anilines has on the stability of the sorbate-β-CD complexes being formed is established. An in-depth thermodynamic analysis of the observed macrocyclic effects is performed and the possibility of using the Abraham solvation model for quantitative descriptions of the complexation constants from the viewpoint of the occurrence of different types of intermolecular interactions in a chromatographic system is demonstrated. It is concluded that introducing additions of β-CDs into a water-methanol mobile phase shortens the retentions times and is accompanied by an increase in the selectivity of chromatographic separation in a series of isomeric derivatives of aniline.

Prediction of analytes' electrophoretic mobility in mixed solvent buffers using Abraham solvation parameters

The electrophoretic mobility of analytes in different solvent compositions of the background electrolyte was calculated using a combined version of a previously developed model with the Abraham solvation model for providing predictive equations.

Study of Intermolecular Interactions Involved in Capillary GLC with Liquid Crystal Compounds as Stationary Phases

Abraham's equation was employed in order to investigate nonspecific intermolecular interactions involving liquid crystals. Several aromatic azo derivatives, proved to have liquid crystal behavior, were used as stationary phases in capillary gas chromatography. The polarizability, polarity, hydrophobicity and hydrogen-bond donor or acceptor characters were estimated using the Abraham solvation model. Calculations were based on the isothermal retention times for 25 compounds, in the temperature range between 70˚ and 170˚C, both in the heating and the cooling mode. The descriptors R, � , �� , �� , and logL 16 (Abraham parameters) were converted into orthogonal descriptors following Randi� 's procedure. The above-mentioned properties involve the r, s, a, b and l coefficients, respectively, which were determined by means of multilinear regression applied to the considered set. Following the orthogonalization procedure, the polarizability term (rR*) was found to be statistically insignificant in the case of the studied compounds. Plots of these coefficients vs temperature are discussed, in order to allow estimations regarding the retention mechanism and contributions of polar and Van der Waals interactions. The variation of properties (e.g. polarity, hydrogen-bond donor and hydrogen-bond acceptor character) with temperature was assigned to the changes in the molecular geometry of the compound used as stationary phase.

Prediction of Partition Coefficients of Organic Compounds in Ionic Liquids: Use of a Linear Solvation Energy Relationship with Parameters Calculated through a Group Contribution Method

A group contribution method is proposed to determine linear solvation energy relationship parameters (GC-LSER) in view of estimating the gas-to-ionic liquid partition coefficients and water-to-ionic liquid partition coefficients. Large sets of partition coefficients were analyzed using the Abraham solvation model to determine the contributions of 21 groups: 12 groups characterizing the cations and 9 groups for the anions. The derived equations correlate the experimental gas-to-ionic liquid and water-to-ionic liquid partition coefficient data to within 0.15 and 0.17 log units, respectively. The 21 group-parameters can be used to predict the partition coefficients of solutes in alkyl or functionalized ionic liquids with a good accuracy.

Effect of surfactant counterion and organic modifier on the properties of surfactant vesicles in electrokinetic chromatography

Counterion and organic modifier are two parameters in EKC that can be varied in order to obtain improved solubility, selectivity, and efficiency. The effect of changing surfactant counterion and/or organic modifier on the chromatographic and electrophoretic properties of cetyltrimethylammonium bromide (CTAB)/sodium octyl sulfate (SOS) vesicles is examined in EKC. The vesicles are prepared in a 1:3.66 cationic/ anionic mole ratio for a total surfactant concentration of 69 mM. The cationic CTAB is replaced by cetyltrimethylammonium chloride (CTAC) and the first use of CTAC/SOS vesicles is reported. The mean diameter of the CTAC/SOS vesicles is 96 nm while that of the CTAB/SOS vesicles is 85 nm. A class I modifier (2-amino-1-butanol) and a class II modifier (acetonitrile) have similar effects on the EOF, elution range, methylene selectivity, and the efficiency of the CTAB/SOS vesicles and the CTAC/SOS vesicles. Upon addition of 10% ACN, there is roughly a 10-fold increase in the efficiency of heptanophenone, a model hydrophobic compound, compared to the efficiency using unmodified vesicles. Linear free energy relationship (LFER) analysis using the Abraham solvation model is employed to characterize solute-vesicle interactions. The results suggest that organic modifier-vesicle interactions depend somewhat on the counterion.

Temperature effect on the characteristic solute–solvent retention interactions, calculated with Abraham's solvation model, for 16 GLC stationary phases

Specific stationary phase constants used in Abraham's solvation model were determined by multiple linear regression analysis (MLRA) for 16 stationary phases (SP) at various temperatures. Hydrogen-bond acidity complexes were negligible for all SPs. The influence of temperature on the solute–SP interactions and on its different terms, both nonpolar (or cavity-dispersion), and polar, has been determined for a series of solutes. Good negative-slope straight lines both for the cavity-dispersion vs. T and for the polar contribution vs. T plots were obtained, the former having a much greater slope than the latter. Also, the dependence of the cavity-dispersion and of the polar retention terms for various chemical functions in three SPs at different temperatures was studied. The cavity-dispersion term increased with decreasing temperature, while the polar term was almost temperature independent. At each temperature, the cavity-dispersion term increased with the Z chain length, excellent linear correlations being obtained for every chemical function tested.

Gibbs energy of solution and molecular structural coefficients of 85 solutes on 20 gas chromatographic stationary phases

Molecular structural coefficients of Takács ( S ci ), relative Gibbs solution energies ( y i ), and their respective increments, [ ΔS ci (RX)] and [ Δy i (RX)], with respect to parent RH n-alkanes have been determined using specific retention volumes of 85 solutes on 20 stationary phases at two common temperatures. Fair correlations between all these parameters and the cavity/dispersion, ΔG(C/D), and the polar, ΔG(P), Gibbs solution energy contributions, calculated with Abraham's solvation model, were obtained. It is proved that the polar solute-solvent interactions calculated for several RX chemical functions, according to the model proposed in this work, agree satisfactorily with both the polar and the cavity formation and dispersion contributions to the Gibbs solvation energy for the said RX chemical functions, deduced from Abraham's solvation model. The relationship between y i and S ci was also investigated.