Correlation Gas Chromatography Research Articles

Estimation of the Vaporization Enthalpies and Vapor Pressures of α-Tocopherol and Δ9-Tetrahydrocannabinol via the Use of a Surrogate, Correlation Gas Chromatography, and Synthetic and Retrosynthetic Analysis.

A protocol is proposed that combines the use of the known properties of a surrogate containing various functional groups together with n-alkanes as standards to evaluate the properties of much larger related substances using correlation gas chromatography. An objective of this work is to develop options that circumvent the lack of appropriate vaporization enthalpy standards that can be used for evaluation of various thermodynamic properties of larger complex molecules using gas chromatography. The surrogate in this case is 2,2,5,7,8-pentamethylchroman-6-ol (PMC) and is used to evaluate the vaporization enthalpies and vapor pressures of α-tocopherol (α-TOC) and Δ9-tetrahydrocannabinol (Δ9-THC). The results are compared to the available literature data and to estimated properties. Vaporization enthalpies are also evaluated by a proposed method that involves the use of synthetic and retrosynthetic analysis.

Vaporization Enthalpies and Vapor Pressures of 5α-Androstane and 5α-Cholestane by Correlation Gas Chromatography

Vaporization Enthalpies and Vapor Pressures of 5α-Androstane and 5α-Cholestane by Correlation Gas Chromatography

Correlation gas chromatography and two-dimensional volatility basis methods to predict gas-particle partitioning for e-cigarette aerosols.

E-cigarette aerosols contain a complex mixture of harmful and potentially harmful chemicals. Once released into the environment, they evolve and become new sources of indoor air pollutants that could pose a significant threat to both users and non-users. However, current understanding of the physicochemical properties of e-cigarette aerosol constituents that govern gas-particle partitioning in the atmosphere is limited, making it difficult to estimate the health risks associated with exposure. Here, we used correlation gas chromatography (C-GC) and two-dimensional volatility basis set (2D-VBS) methods to determine the vapor pressures and volatility for commonly reported toxic and irritating e-cigarette aerosol constituents. The vapor pressures of target compounds at 298 K were estimated from the Antoine-type linear relationship between the vapor pressure of reference standards and their retention times. Our C-GC results showed an overall positive correlation (R = 0.84) with estimates using the EPI (Estimation Programs Interface) Suite. The volatility calculated by 2D-VBS correlates well with the calculated vapor pressure from both C-GC (R = 0.82) and EPI Suite (R = 0.85). The volatility distribution also indicated fresh e-cigarette aerosol constituents are mainly more volatile organic compounds. Our case study revealed that low-vapor-pressure compounds (e.g., σ-dodecalactone, γ-decalactone, and maltol) become enriched in the e-cigarette aerosols within 2 hours following vaping emissions. Overall, these findings demonstrate the applicability of the C-GC and 2D-VBS methods for determining the physiochemical properties of e-cigarette aerosol constituents, which can aid in assessing the dynamic chemical composition of e-cigarette aerosols and exposures to vaping emissions in indoor environments.

The vaporization enthalpies and vapor pressures of Vescepa® and related unsaturated marine FAME by correlation gas chromatography

This article combines data from two previous reports together with new data dealing with the vaporization enthalpies and vapor pressures of a series of saturated and unsaturated fatty acid methyl ester(s) (FAME) by correlation gas chromatography. The work updates earlier results using newly proposed vaporization enthalpies for the saturated FAME used as standards in previous work. This update also provides some insight into the requirements necessary for appropriate column and standard selection for experiments using correlation gas chromatography. Vaporization enthalpies and vapor pressures for saturated FAME methyl heneicosanoate, methyl docosanoate, and methyl tetracosanoate are re-evaluated and together with proposed literature values for methyl tetradecanoate to methyl eicosanoate, are used to evaluate similar properties for a series of unsaturated fatty acid esters. Updated results on the vaporization enthalpies and vapor pressures of a number of unsaturated fatty acid methyl esters (FAME) found in marine oil are reported including several relatively reactive omega-3-polyunsaturated esters. Omega-3-FAME include methyl (9,12,15)Z-octadecatrienoate, methyl (5,8,11,14,17)Z-eicosapentaenoate, and methyl (4,7,10,13,16,19)Z-docosahexenoate among other unsaturated methyl esters. Also included in the study of the omega-3-unsaturated esters is the drug Vescepa®, ethyl (5,8,11,14,17)Z-eicosapentaenoate, a drug used to lower triglyceride levels.

A correlation gas chromatographic study of the vaporization enthalpies and vapor pressures of patchoulol and 2-tetradecanol and estimations of their sublimation properties

The vaporization enthalpy and vapor pressure near ambient temperatures of patchoulol, present in patchouli oil, are evaluated by correlation gas chromatography. Additionally, the vaporization enthalpy of 2-tetradecanol, used initially as a standard is also evaluated using a series of 1-alkanols. While the vaporization enthalpy evaluated differs from the literature value, the vapor pressures of 2-tetradecanol are found to be in good agreement with the literature over a broad range of temperatures. Fusion enthalpies of both of these low melting substances are estimated and used to calculate their sublimation enthalpies and vapor pressures at T = (Tfus and T = 298.15) K. The results are compared to available literature data, most of which was also estimated. Agreement with existing literature values is quite good.

The Vaporization Enthalpy and Vapor Pressure of (±) N-Ethyl Amphetamine by Correlation Gas Chromatography.

The vaporization enthalpy, and vapor pressure as a function of temperature of N-ethylamphetamine, a substance used in the 1950s as an appetite suppressant and more currently abused as a designer drug, is reported. Its physical properties are compared to those of S (+)-N-methamphetamine, a substance whose physiological properties it mimics. A vaporization enthalpy of (62.4 ± 4.4) kJ·mol−1 and vapor pressure of (19 ± 11) Pa at T = 298.15 K has been evaluated by correlation gas chromatography. Results are compared to estimated values and to the limited amount of experimental property data available.

Vaporization enthalpies and vapor pressures of the major components of opopanax oil, α-santalene, cis α-bisabolene, cis α-bergamotene

The vapor pressures and vaporization enthalpies of the major components of opopanax oil, a medicinal that has been in use since biblical times, are evaluated by correlation gas chromatography. Two sets of hydrocarbon standards are used, n-alkanes and a mixture of cyclic and polycyclic hydrocarbons. Two of the oil’s sesquiterpene components, evaluated in a previous study, were used both as standards and also as targets. Their use as targets was in an effort to confirm both their identity in the oil and the reproducibility of their properties. All correlations produce reproducible vaporization enthalpies and vapor pressures at ambient temperatures. At elevated temperatures, the use of the two different sets of standards resulted in some divergence in vapor pressure. Experiments are described aimed at attenuating this divergence. The results are compared to existing data.

Vaporization enthalpy and liquid vapor pressure of bicifadine using correlation gas chromatography

Bicifadine has been used for the treatment of acute and persistent pain. The vaporization enthalpy and the vapor pressure of bicifadine were evaluated using correlation gas chromatography with secondary amines as standard compounds. A vaporization enthalpy of (73.3 ± 5.0) kJ·mol−1 and a vapor pressure of (1.29 ± 0.64) Pa were obtained for bicifadine at T = 298.15 K. The estimated boiling temperature of (563 ± 3) K was predicted by extrapolation.

The vapor pressure and vaporization enthalpy of (−) β-Elemene and (−) β-Bisabolene by correlation gas chromatography

The vaporization enthalpies and vapor pressures of (−) β-elemene and (−) β-bisabolene are evaluated by correlation gas chromatography using two sets of standards, a mixture of various cyclic hydrocarbons and a series of n-alkanes. Both compounds are sesquiterpenes found in a variety of plants. β-Elemene has been used in China for the treatment of a variety of cancers. β-Bisabolene is used as a flavoring agent and it has also been shown to exhibit cytotoxicity in breast cancer cell lines, both in vitro and in vivo. Vaporization enthalpies of [(66.8 ± 3.0) and (73.9 ± 3.0)] kJ·mol−1 and vapor pressures of [(3.1 ± 1.0) and (0.72 ± 0.2)] Pa at T = 298.15 K have been evaluated for (−) β-elemene and (−) β-bisabolene, respectively. Vapor pressures were also evaluated as a function of temperature from T = (298.15–450) K and fit to a second order polynomial.

The vapor pressure and vaporization enthalpy of pristane and phytane by correlation gas chromatography

The vapor pressure and vaporization enthalpy of pristane and phytane, two compounds of interest to paleobotanists investigating the antiquity of life, have been evaluated and compared to existing values by correlation gas chromatography. Vapor pressures have been evaluated from T = (298.15–550) K for both pristane and phytane. Both sets of values were fit to a second order polynomial. Comparison with existing literature values for pristane over the temperature range T = (315–452) K are generally in agreement as is the vaporization enthalpy evaluated at the mean experimental temperature reported in the literature, T = 383.4 K. Similar experimental properties for phytane are not available. Comparison of vapor pressures and vaporization enthalpy of a structurally similar isomer of phytane, however, are quite good.

Vapor pressure and vaporization enthalpy studies of the major components of ginger, α-zingiberene, β-sesquiphellandrene and (−) ar curcumene by correlation gas chromatography

The vaporization enthalpies and vapor pressures of three major components in ginger, α-zingiberene, β-sesquiphellandrene, and (−) ar-curcumene are evaluated by correlation gas chromatography using two set of standards, n-alkanes and a series of cyclic and polycyclic hydrocarbons. Vaporization enthalpies are reproduced by both sets of standards. Vapor pressures as a function of temperature are fit to a second order polynomial and the results compared to available literature data. Vapor pressures as evaluated by both sets of standards are in general agreement at ambient temperatures but begin to diverge somewhat at elevated temperatures. The n-alkanes appear to provide the best agreement with the limited amount of available experimental data.

The vapor pressure and vaporization enthalpy of squalene and squalane by correlation gas chromatography

Vapor pressures and vaporization enthalpies of both squalane and squalene are evaluated by correlation gas chromatography using n-alkanes as standards. Vapor pressures as a function of temperature from T = (298.15–600) K are fit to a second order polynomial. Vaporization enthalpies of (134.4 ± 2.4 and 139.8 ± 2.4) kJ mol−1 and vapor pressures of p = ((15 ± 5.4) and (3.7 ± 1.3))·10−7 Pa at T = 298.15 K are evaluated for squalane and squalene, respectively. Vapor pressures are compared with existing literature data. Enthalpies of interaction with the column are evaluated for all analytes and are found to be endothermic at the mean temperatures of the chromatography.

An examination of vaporization, fusion and sublimation enthalpies of tolazoline using correlation gas chromatography and differential scanning calorimetry

Tolazoline is a vasodilator that is used to treat spasms in peripheral blood vessels and to treat convulsive symptoms. The vaporization, fusion and sublimation enthalpies of tolazoline at T = 298.15 K have not been reported. Correlation gas chromatography experiments were first performed to identify appropriate standards that could be used for materials containing similar substituents. Subsequent correlations resulted in a vaporization enthalpy, \(\Delta_{\text{l}}^{\text{g}}\)H(298.15 K) of (89.9 ± 5.5) kJ mol−1 for tolazoline. A fusion enthalpy, \(\Delta_{\text{cr}}^{\text{l}}\)H(337.4 K) of (16.2 ± 0.4) kJ mol−1, was measured by differential scanning calorimeter and adjusted to T = 298.15 K. Combination of vaporization enthalpy and fusion enthalpy resulted in sublimation enthalpy, \(\Delta_{\text{cr}}^{\text{g}}\)H(298.15 K), of (103.9 ± 5.5) kJ mol−1.

Vapor pressure and vaporization enthalpy studies of (+)-longifolene, (−)-isolongifolene and β-myrcene by correlation gas chromatography

This paper examines the use of two different sets of standards, n-alkanes and a more structurally diverse group of cyclic and polycyclic molecules to evaluate the vaporization enthalpies and vapor pressures of (+) longifolene(−)-isolongifolene and β-myrcene using correlation gas chromatography. Both sets of standards provide similar vaporization enthalpies and vapor pressures of the title compounds at T = 298.15 K within their experimental uncertainties. The group of cyclic and polycyclic hydrocarbons reproduce the vapor pressures of the sesquiterpene hydrocarbons at elevated temperatures best while the same properties of β-myrcene are best reproduced by the n-alkanes as judged by reproduction of both experimental boiling temperatures measured at reduced pressures and vapor pressures. The results confirm previous findings obtained on polycyclic hydrocarbons regarding the suitability of using structurally similar standards and suggest that n-alkanes are suitable vapor pressure standards for highly unsaturated acyclic hydrocarbons.

Vaporization enthalpy and vapor pressure of (−) Ambroxide and Galaxolide by correlation gas chromatography

The vapor pressures and vaporization enthalpies of dibenzofuran, (−) Ambroxide™ and Galaxolide™ are evaluated by correlation gas chromatography. (−) Ambroxide™ and Galaxolide™ are important commercial products, the latter of which has been the subject of some controversy regarding its impact on the environment. All are cyclic ethers. Dibenzofuran, with established literature values was chosen to evaluate the effectiveness of using hydrocarbons to evaluate both vaporization enthalpies and liquid vapor pressures of simple ethers. Vaporization enthalpy results on dibenzofuran are consistent with the literature value. Current results suggest that hydrocarbons can also be employed to successfully evaluate both liquid vapor pressures and vaporization enthalpies at ambient temperatures for substances for this class of compounds if suitable standards are unavailable.

Thermochemical properties of sesquiterpenes in natural products by correlation gas chromatography: Application to bergamotene oil

Abstract The vapor pressures and vaporization enthalpies of the three major components of bergamotene oil have been evaluated by correlation gas chromatography. Three major components were identified by GCMS as E β-caryophyllene, trans α-bergamotene and α-humulene. Two of the components, E β-caryophyllene and α-humulene were also evaluated using commercial caryophyllene samples. Z-caryophyllene, present in the commercial sample was also evaluated. Two sets of hydrocarbon standards, n-alkanes and a series of relatively unrelated cyclic compounds that included adamantane and two alkyl derivatives, (−) α-pinene, diamantane and 1,4-di-t-butylbenzene, were used. Vaporization enthalpies of the targets at T = 298.15 K were reproduced within the specified uncertainties by both sets of standards as were vapor pressures from T = (298.15 to ∼400)K. Above 400 K, vapor pressures diverged. Equations for the evaluation of vapor pressure as a function of temperature are reported for all four compounds investigated.

The vaporization enthalpy and vapor pressures of liquid adamantane, diamantane and α- and β-cedrene by correlation gas chromatography

This work examines the use of two different sets of standards to evaluate vaporization enthalpies and liquid vapor pressures of a series of polycyclic hydrocarbons that include adamantane, diamantane, and α and β-cedrene by correlation gas chromatography. Several n-alkanes and a series of cyclic and polycyclic hydrocarbons were selected as standards to independently evaluate the appropriateness of using n-alkanes to evaluate these properties in two branched polycyclic sesquiterpenes. Vapor pressures of two of the polycyclic hydrocarbons examined, 1,3-dimethyladamantane and 1,4-di-t-butylbenzene, are known and the results obtained using n-alkanes as standards were used for comparisons. Standards for evaluation of adamantane and diamantane included these two compounds along with α-pinene, and camphene; a series of n-alkanes were also used in separate experiments for evaluation of the adamantanoids. The n-alkane standards included decane and dodecane through to pentadecane. Vapor pressures for adamantane and diamantane evaluated in this work were combined with literature values for 1,3-dimethyladamantane and 1,4-di-t-butylbenzene at elevated temperatures to also evaluate liquid vapor pressures and vaporization enthalpies for α- and β-cedrene. The results were compared to those evaluated independently using n-alkanes. The results of the experiments are discussed.

Evaluation of vaporization enthalpies and liquid vapor pressures of cedrol, nerolidol, and 1-adamantanol by correlation gas chromatography

The vaporization enthalpies and vapor pressures of (+)-cedrol and nerolidol are reported at T=298.15K using a series of alcohols as standards by correlation gas chromatography. Vaporization enthalpies at T=298.15K of (88.3±1.5, 91.4±1.5, 92.7±1.6) kJ·mol−1 were evaluated for (+)-cedrol, Z-nerolidol and E-nerolidol, respectively. Upon injection into the gas chromatograph, (+)-cedrol was partially converted to α- and β-cedrene, identified by GCMS and independent synthesis. Additionally, the vaporization enthalpy of 1-adamantanol evaluated as an unknown and then used as a standard, compared well to the value calculated from the sublimation, fusion and solid-solid phase transition enthalpies previously reported. Liquid vapor pressures of (+)-cedrol, Z-nerolidol, E-nerolidol and 1-adamantanol are also reported as a function of temperature. A vapor pressure of 187.9kPa is estimated for 1-adamantanol at the fusion temperature and the vapor pressure of solid 1-adamantanol at T=298.15K is reproduced within a factor of two of the literature value.

Enthalpy of vaporization and vapor pressure of whiskey lactone and menthalactone by correlation gas chromatography

Enthalpies of vaporization at T=298.15K of cis and trans-whiskey lactone have been evaluated by correlation gas chromatography to be (68.4±1.7)kJ·mol−1 and (67.5±1.7)kJ·mol−1, respectively. The enthalpies of vaporization of isomintlactone and mintlactone also evaluated by correlation gas chromatography have been found to have vaporization enthalpies of (74.2±1.8)kJ·mol−1 and (73.2±1.8)kJ·mol−1 respectively. The vapor pressures for cis and trans-whiskey lactone at T=298.15K have been evaluated as (1.5±0.09)Pa and (2.0±0.1)Pa using vapor pressures of a series of lactones as standards. Vapor pressures for isomintlactone and mintlactone were evaluated as (0.26±0.012)Pa and (0.33±0.02)Pa, respectively. Fusion and sublimation enthalpies for (+)-isomintlactone as well as the vapor pressure of the solid have been estimated.

Vapor pressures and vaporization enthalpy of (−) α-bisabolol and (dl) menthol by correlation gas chromatography

The vapor pressures and vaporization enthalpies of (−) α-bisabolol and (dl)-menthol, two GRAS chemicals (generally recognized as safe) are evaluated by correlation gas chromatography using a series of saturated primary alcohols as standards. Vaporization enthalpies of (96.6±2.4) and (74.2±2.8)kJmol−1 and vapor pressures of p/Pa=(0.020±0.003) and (4.5±0.44) were evaluated at T=298.15K for (−) α-bisabolol and (dl)-menthol, respectively, and compared to literature values. The vapor pressures of both compounds from T=(298.15 to 500)K have been derived from correlations using vapor pressures of a series of 1-alkanols and corresponding gas chromatographic retention times at 10K intervals. The results were fit to a second order polynomial. Calculated normal boiling temperatures of TB=(574.8 and 492.7)K are calculated for (−) α-bisabolol and (dl)-menthol, respectively. A normal boiling temperature of TB=(485.2, and 489.7)K has previously been reported for (dl)-menthol. Vapor pressures for both (l)-menthol and (dl)-menthol from a previous study and (dl)-menthol from this study are compared with literature values.