Gas-liquid Chromatographic Data Research Articles

A Revisited Definition of the Three Solute Descriptors Related to the Van der Waals Forces in Solutions

It is currently admitted that the intermolecular forces implicated in Gas Liquid Chromatography (GLC) can be expressed as a product of parameters (or descriptors) of solutes and of parameters of solvents. The present study is limited to those of solutes, and among them the three ones are involved in the Van der Waals forces, whereas the two ones involved in the hydrogen bonding are left aside at this stage. These three studied parameters, which we call δ, ω and ε, respectively reflect the three types of Van der Waals forces: dispersion, orientation or polarity strictly speaking, and induction-polarizability. These parameters have been experimentally obtained in previous studies for 121 Volatile Organic Compounds (VOC) via an original Multiplicative Matrix Analysis (MMA) applied to a superabundant and accurate GLC data set. Then, also in previous studies, attempts have been made to predict these parameters via a Simplified Molecular Topology procedure (SMT). Because these last published results have been somewhat disappointing, a promising new strategy of prediction is developed and detailed in the present article.

Solvation parameters: Part 1. Mutual improvements of several approaches and determination of two first sets of optimized values

An improvement in the characterization and the determination of the solvation parameters allows, not only a better knowledge of solutions, but also of some biological phenomena. In this paper, we test several published data and approaches in the field of solubility and solvation parameters in two ways: (i) the mutual independence of the parameters and (ii) their ability to take into account recently published gas–liquid chromatographic data. From this enquiry it arises that the most suitable published values are those of Abraham concerning 314 solutes. It also arises that the parameters of dispersion and orientation of this published data set are appreciably improved using two simple equations. In addition, a new set of optimized values for 133 solutes is given, by derivation from retention indices in gas–liquid chromatography (GLC) on five selected stationary phases, published by Kováts and co-workers and in the present study. The two sets have a total of 373 defined compounds.

Use of Near‐Infrared Reflectance Spectroscopy for Selecting for High Stearic Acid Concentration in Single Husked Achenes of Sunflower

Half‐seed analysis by gas‐liquid chromatography (GLC) allows a nondestructive evaluation of the fatty acid composition of oilseeds, since in most cases the analyzed portion is representative of the whole seed. However, the sunflower (Helianthus annuus L.) mutant CAS‐14 exhibits a high stearic acid concentration nonuniformly expressed along the longitudinal axis of the seed. No analytical technique is available for nondestructive selection at the single seed level in this mutant. The objective of the present research was to study the potential of near‐infrared reflectance spectroscopy (NIRS) for analyzing the fatty acid composition of single husked achenes of sunflower and to evaluate its performance in a selection program for high stearic concentration in materials derived from CAS‐14. A calibration set containing 2510 single husked achenes from a broad spectrum of breeding materials was developed. Reliable equations were developed for stearic acid, with r2 = 0.80 and ratio of the standard error of cross validation (SECV) to the standard deviation (SD) of 0.45, oleic acid (r2 = 0.89, SECV/SD = 0.34), and linoleic acid (r2 = 0.91, SECV/SD = 0.30). The calibration equations were applied to the analysis of 8109 husked achenes within a selection program for high stearic acid concentration, 503 of them being further analyzed by GLC to monitor the performance of NIRS. The results revealed a close relationship between NIRS and GLC data, with r2 of 0.83 for stearic acid, 0.92 for oleic acid, and 0.93 for linoleic acid concentration. It was concluded that NIRS can be used reliably for nondestructive selection for these major fatty acids at a single‐seed level.

The determination of air/water partition coefficients for alkyl carboxylic acids by a new indirect method.

The air/water partition coefficients of carboxylic acids, Kw, especially those of high molecular weight, are very difficult to determine directly. Values of Kw can be obtained by an indirect method as Kw = K/P where K is an air/solvent partition coefficient and P is the corresponding water/solvent partition coefficient. In the present method, gas-liquid chromatographic data and water/solvent partition data are used to obtain 'descriptors' of carboxylic acids that can then be used to determine the required K, P, and thus Kw values. These are reported for all the 24 n-alkyl carboxylic acids from formic acid to n-tetracosanoic acid, and for seven branched chain alkyl carboxylic acids. There is good agreement with literature values of Kw, where available, although the present data on the n-alkyl carboxylic acids is much more self consistent than the literature data.

Structures, practical sources (gymnosperm seeds), gas-liquid chromatographic data (equivalent chain lengths), and mass spectrometric characteristics of all-cis Δ5-olefinic acids

Structures, practical sources (gymnosperm seeds), gas-liquid chromatographic data (equivalent chain lengths), and mass spectrometric characteristics of all-cis Δ5-olefinic acids

Structures, practical sources (gymnosperm seeds), gas-liquid chromatographic data (equivalent chain lengths), and mass spectrometric characteristics of all-cis Δ5-olefinic acids

In view of the increasing interest of lipid researchers in the biological effects of all-cis Δ5-unsaturated polymethylene-interrupted fatty acids (Δ5-UPIFA) from vegetable origin, this paper is concerned with their occurrence in practical sources (gymnosperm seeds), structures, and identification by gas-liquid chromatography (GLC) and mass spectrometry (MS). The use of equivalent chain lengths (ECL) determined by calculations based on available standards, in close agreement with data determined with easily available commercial gymnosperm seeds specific for each Δ5-UPIFA, allows identification of all Δ5-UPIFA. These tentative identifications are supported by GLC-MS of the appropriate (4, 4-dimethyloxazoline and picolinyl ester) derivatives. ECL are particularly useful to identify Δ5-UPIFA in tissue lipids from animals experimentally fed oils containing these acids, with no interference with polyunsaturated fatty acids of endogenous origin.

Estimation of seed weight, oil content and fatty acid composition in intact single seeds of rapeseed ( Brassica napus} L.) by near-infrared reflectance spectroscopy

The potential of near-infrared reflectance spectroscopy (NIRS) for the simultaneous analysis of seed weight, total oil content and its fatty acid composition in intact single seeds of rapeseed was studied. A calibration set of 530 single seeds was analysed by both NIRS and gas-liquid chromatography (GLC) and calibration equations for the major fatty acids were developed. External validation with a set of 75 seeds demonstrated a close relationship between NIRS and GLC data for oleic (r = 0.92) and erucic acid (r = 0.94), but not for linoleic (r = 0.75) and linolenic acid (r = 0.73). Calibration equations for seed weight and oil content were developed from a calibration set of 125 seeds. A gravimetric determination was used as reference method for oil content. External validation revealed a coefficient of correlation between NIRS and reference methods of 0.92 for both traits. The performance of the calibration equations for oleic and erucic acid was further studied by analysing two segregating F2 seed populations not represented in the calibration set. The results demonstrated that a reliable selection for both fatty acids in segregating populations can be made by using NIRS. We concluded that a reliable estimation of seed weight, oil content, oleic acid and erucic acid content in intact, single seeds of rapeseed is possible by using NIRS technique.

Volatile fatty acids, metabolic by-products of periodontopathic bacteria, inhibit lymphocyte proliferation and cytokine production.

Short-chain fatty acids are a major by-product of anaerobic metabolism and can be detected in gingival fluid from periodontal pockets. Since most T cells are present subjacent to the pocket epithelium in conjunction with the plasma cells, it is important to know how these T cells are affected by short-chain fatty acids produced by subgingival plaque. The purpose of this study is to examine the effects of extracellular metabolites from periodontopathic bacteria on the proliferation and cytokine production of mouse splenic cells as a potential mechanism of imbalance among host-microbial interactions. A low-molecular-weight, heat-stable agent present in the two-day culture filtrate of Porphyromonas gingivalis, Prevotella loescheii, and Fusobacterium nucleatum significantly depressed Con A- and LPS- induced cell proliferation. To determine whether short-chain fatty acids present in the filtrate could account for the depression, we tested extracted volatile and non-volatile fatty acids for their effects on mitogenic activity. The volatile fatty acids extracted from immunosuppressive supernatants greatly inhibited T- and B- cell proliferation. Among these volatile fatty acids, butyric, propionic, valeric, and isovaleric acids impaired cell proliferation dose-dependently. From gas-liquid chromatographic analysis data, it is suggested that immuno-inhibitory activities in culture filtrates are mainly attributable to butyric and isovaleric acids in P. gingivalis, to propionic, butyric, and isovaleric acids in P. loescheii, and to butyric acid in F. nucleatum. Furthermore, these fatty acids significantly depressed interleukin 2 (IL-2), IL-4, IL-5, IL-6, and IL-10 production by Con A-stimulated splenic-T cells dose-dependently.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of Plasma Lipids in Patients With Malignant Disease by 13C Nuclear Magnetic Resonance Spectroscopy and Gas Liquid Chromatography

The purpose of this study was to characterize possible changes in fatty acid composition of plasma lipids associated with malignancy. The very low, low, and high-density lipoproteins were isolated by gradient density ultracentrifugation of plasma from 16 patients with malignant disease and from 15 controls. The triglyceride, esterified cholesterol, and phospholipid constituents of each lipoprotein fraction were isolated, and the fatty acid composition within each lipid component was determined by gas liquid chromatography (GLC). In the 10- to 45-parts-per-million (ppm) region of the carbon-13 (13C) nuclear magnetic resonance (NMR) plasma spectrum, differences were found between patients with malignant disease and controls. The ratio of the 31.6/32.1 ppm resonance intensities was lower in the group of cancer patients. The ratio of the 24.4/24.9 ppm resonance intensities in patients with malignant disease was different from the nonpregnant controls. The NMR changes were interpreted in light of GLC data that indicated derangements in the composition of fatty acids within lipoprotein lipids. In total plasma esterified cholesterol, the relative amount of linoleic acid (18:2, n-6) was lower, whereas oleic acid (18:1, n-9) was higher in the group of patients with malignant disease. In total plasma triglycerides, the amount of oleic acid was higher in the cancer patient group. For total plasma phospholipids, no differences in fatty acid composition between patients and controls were found. Throughout the lipoprotein fractions, the same differences in oleic acid and linoleic acid distribution for triglyceride and esterified cholesterol were found when comparing cancer and control subjects. In conclusion, we found that there are certain differences in the 13C NMR spectra and fatty acid profiles between a small and heterogeneous group of cancer patients after they have received their initial treatment and a group of healthy controls. We suggest that carbon NMR spectroscopy could be useful in characterizing malignancy-associated lipid changes.

Determination of second cross virial coefficients from gas-liquid chromatographic data: II. Dilute mixtures of water and brominated hydrocarbons

Gas-liquid Chromatographic measurements were carried out in the temperature range 298–323 K and were used to determine the second cross virial coefficients for each brominated hydrocarbon-carrier gas mixture studied. Measurements on mixtures of brominated compounds infinitely dilute in water were made using a gas-liquid Chromatographic apparatus with a packed column under carrier gas inlet pressures up to 700 kPa and with water as the stationary phase. Nitrogen was used as the carrier gas. In addition, mixtures of water infinitely dilute in the brominated compounds were studied using an isopiestic apparatus. Henry's constants were also derived and group interaction parameters for the UNIFAC correlation were estimated using the experimental infinite dilution activity coefficients. The new group interaction parameters were used to predict activity coefficients for a range of brominated hydrocarbon-water mixtures.

Hydrogen bonding: XXVII. Solvation parameters for functionally substituted aromatic compounds and heterocyclic compounds, from gas—liquid chromatographic data

The truncated solvation equation log SP = c + rR 2 + l log L 16 has been applied to a very large number of sets of gas—liquid chromatographic data on non-polar stationary phases. Here, log SP can be log V G or can be the retention index I. R 2 is the excess molar refraction of the solute and c, r and l are constants. A set of solutes of known log L 16 values is used to construct the equation, and then further values of log L 16 can be obtained for any solute of known log SP value. In this way, new log L 16 values for over 1000 solutes have been obtained. Then knowing log L 16, and R 2, the equation log SP = c + rR 2 + sπ 2 H + l log L 16 ( s is a constant) can be applied to GLC data on polar non-acidic stationary phases, and the dipolarity/polarisability parameter, π 2 H determined similarly. Values of π 2 H for over 700 compounds are reported, including those for functionally substituted aromatic compounds and heterocyclic compounds. It is shown that π 2 H, is a blend of dipolarity/polarisability, and cannot simply be calculated from solute dipole moments.

A method for tentative identification of unknown gas chromatographic peaks by retention index

A method for gaining structural information from gas-liquid chromatographic or radiochromatographic data, using the structure-retention index relationship (SRIR), is reported. The method can be applied to predict the retention indexes of a wide range of apolar and polar compounds and the silylated derivatives of polar compounds.

Hydrogen bonding: XXI. Solvation parameters for alkylaromatic hydrocarbons from gas-liquid chromatographic data

The truncated solvation equation log SP = c + rR 2 + llog L 16 has been applied to numerous sets of gas-liquid chromatographic (GLC) data for alkylaromatic hydrocarbons on non-polar stationary phases. Here SP can be V G or can be the relative retention time, and the retention index I can in this context be used in place of log SP. R 2 is the solute excess molar refraction, easily obtained from refractive index. A set of solutes of known log L 16 is used to set up the equation and then values of log L 16 can be back-calculated for other solutes: L 16 is originally defined as the solute gas-liquid partition coefficient on hexadecane at 25°C. Through the above equation log L 16 values were calculated for 190 solutes. Once log L 16 is known, the reduced equation log SP = c + sπ H 2 + llog L 16 can be applied to GLC data on polar stationary phases, and the dipolarity/polarizability parameter π H 2 obtained by back-calculation in a similar way. Values of π H 2 for 120 solutes are listed. It is shown that n-alkyl substituents affect the π H 2 value only slightly, but ortho substituents considerably increase π H 2, e.g., benzene (0.52), toluene (0.52), o-xylene (0.56), 1,2,3-trimethylbenzene (0.61), 1,2,3,4-tetra-methylbenzene (0.65), pentamethylbenzene (0.66), hexamethylbenzene (0.72).

Synthesis and Characterization of Monoethoxymethamphetamines

ABSTRACTThe monoethoxymethamphetamines were synthesized from the (E)-monoethoxy-1-(2-nitro-1-propenyl)benzenes via the corresponding 1-phenyl-2-propanones. The gas-liquid chromatographic (GLC) data, and ultraviolet (UV), infrared (IR), proton magnetic resonance (1H-NMR), carbon-13 magnetic resonance (13C-NMR) and mass spectra (MS) are presented for the 1-phenyl-2-propanones as well as the methamphetamines.

Synthesis and Spectral Properties of 2,5-Dimethoxy-4-Ethoxyamphetamine and Its Precursors

Abstract 2,5-Dimethoxy-4-ethoxyamphetamine (MEM) was synthesized by two routes. The gas liquid chromatographic data and ultraviolet, infrared, proton magnetic resonance, carbon-13 magnetic resonance, and mass spectra are presented for this amphetamine as well as its precursors. This amphetamine was found to be identical to the sample submitted by the police.

CHEMICAL AND PHYSICAL PROPERTIES OF (Z)—AND (E) -MONOETHOXY-1-(2-NITRO-1-PROPENYL) BENZENES: Important Precursors to the monoethoxyamphetamines

(Z)-Monoethoxy-1- (2-nitro-1-propenyl)benzenes were synthesized from the corresponding (E)-isomers by irradiation with light in toluene in the presence of benzophenone. The gas-liquid chromatographic (GLC) and thin-layer chromatographic (TLC) data, and ultraviolet (UV), infrared (IR), proton magnetic resonance (1H-NMR), and mass spectra (MS) are presented for both isomers for comparison. The (Z)-isomer is partially converted on the injector of GLC apparatus to the (E)-isomer.

Effects of Tertiary Butylhydroquinone on Storage Stability of Canola Oil. II. Practical Storage

The sensory (odor and flavor), chemical (peroxide and thiobarbituric acid values) and gas liquid chromatography (GLC) characteristics of tertiary butylhydroquinone (TBHQ) treated canola oils, stored in clear and amber glass bottles in the presence of light (1400 lux) for up to 16 w, were determined. In addition, odor and chemical characteristics of the TBHQ treated oils in clear bottles stored in the dark for up to 16w were determined. Chemical and GLC data indicated that TBHQ retarded oxidative changes; however, this protective effect was not reflected in sensory odor and flavor scores. TBHQ may increase the storage stability of canola oil; however, the relationship between sensory and chemical/GLC data requires further study. Oils stored in clear bottles (in presence of light) had greater oxidative changes than those in amber glass bottles. Oil samples in clear bottles stored in the absence of light maintained almost unchanged high quality during the entire storage period. Therefore, to maintain oil quality, canola oil should be protected from light.

Application of an enzyme-linked immunosorbent assay for screening of T-2 toxin-producing Fusarium spp.

Culture filtrates of Fusarium species were subjected without clean-up procedures to an indirect competitive enzyme-linked immunosorbent assay with anti-T-2 toxin monoclonal antibody. Fusarium sporotrichioides, F. poae, F. tricinctum, and F. culmorum strains were positive for T-2 toxin, with a minimum detection limit of 5 pg per assay (100 pg/ml of culture filtrate), and the assay data correlated well with the gas-liquid chromatographic data.

Characterization of Mycobacterium paratuberculosis by gas-liquid and thin-layer chromatography and rapid demonstration of mycobactin dependence using radiometric methods.

Thirty-six Mycobacterium paratuberculosis isolates of bovine, caprine, and ovine origins were evaluated by using gas-liquid chromatography (GLC), thin-layer chromatography (TLC), and BACTEC 7H12 Middlebrook TB medium (12A; Johnston Laboratories, Inc., Towson, Md.) in an effort to more rapidly differentiate this group of organisms from other mycobacteria. Bacterial suspensions (0.1 ml) were inoculated by syringe into 7H12 broth containing 2 micrograms of mycobactin P per ml and control broth without mycobactin P. Cultures were incubated at 37 degrees C and read daily with a BACTEC Model 301 (Johnston Laboratories). After 8 days of incubation, the growth index readings for the test broths containing mycobactin P were twice those of the control broths without mycobactin P. Sixty-five isolates of mycobacteria other than M. paratuberculosis were also examined. No difference was noted between the growth index readings of control and mycobactin-containing broths. Except for Mycobacterium avium-Mycobacterium intracellulare, TLC studies differentiated M. paratuberculosis from the other mycobacterial species tested. The GLC data reveal that all M. paratuberculosis isolates had a distinctive peak (14A) which was not found among M. avium-M. intracellulare complex organisms. These data indicate that 7H12 radiometric broth was able to rapidly demonstrate the mycobactin dependence of M. paratuberculosis and GLC and TLC procedures were capable of rapidly differentiating this organism from the other mycobacteria studied.

A Method for Measuring the Self-Cementing Characteristics of Fly Ash Pastes

SUMMARYThe development of an improved method of trimethylsilylation [1] made possible the assessment of different polysilicate fractions in hydrated cement pastes, as a means of structural characterization. Several laboratories have presented various gas-liquid chromatographic data on the polysilicate derivatives of C-S-H [2–5]. Identification of the different molecular weight fractions has been made, in most laboratories, by matching the gasliquid chromatographic peaks with the gel permeation chromatographic peaks. The success of this matching process is always dependent on type of instruments, length of columns and temperature range.In the present investigation, a mass spectrometer, in direct contact with the gas-liquid chromatograph, was used to identify the molecular weight of each of the fractions separated from the chromatograph. The technique was applied to determine the molecular weights and abundances of different polysilicate species in hydrated fly ash pastes.