High performance liquid chromatography of fatty methyl esters: Analytical separations

Fatty methyl esters are separated on the basis of unsaturation and chain length on an analytical scale by high performance liquid chromatography with a C18/Corasil column and aqueous acetonitrile solvent. Analysis by this method includes polymerized and oxidized esters which may not be detected by gas chromatography.     

The purification of fatty acid methyl esters by high pressure liquid chromatography

Procedures are described for the rapid purification of gram quantities of methyl oleate, methyl linoleate, methyl α- and γ-linolenates and methyl ricinoleate from appropriate natural oils by high pressure liquid chromatography (HPLC).     

Separation ofCis andTrans isomers by reverse phase high pressure liquid chromatography

A reverse phase high pressure liquid chromatography procedure was devised for the analytical or preparative separation of geometric isomers of dodecenyl acetates, tetradecenyl acetates, hexadecenyl acetates, tridecadienyl acetates, and methyl oleate and elaidate. Use of μ Bondapak C-18 permitted the separation of these isomers. ARS, USDA.     

High performance liquid chromatography of triglycerides: Controlling selectivity with reverse phase columns

Rapid separations of triglycerides by chain length and degree of unsaturation have been made by high performance liquid chromatography (HPLC) using reverse phase columns. Several different bonded columns were evaluated for use in reverse phase HPLC of triglycerides, and differences in selectivity are discussed. Selectivity was also modified by adding silver ion to the solvent, which produces marked changes in selectivity of solute triglycerides. Presented at the AOCS meeting in San Francisco, May 1979.     

Silver nitrate-high performance liquid chromatography of fatty methyl esters

Long chain fatty methyl esters have been separated by high performance liquid chromatography on the basis of number, position, and geometric configuration of double bonds with a silver nitrate-silicic acid column and benzene solvent. Saturated esters are eluted first, followed by methyl elaidate and then methyl oleate. Geometric isomers of methyl 9,12-octadecadienoate and of methyl 9,15-octadecadienoate are also well separated. Methyl linolenate is retained strongly on the column and its elution has not been observed, but thetrans, trans, trans andtrans, cis, trans isomers are separated.     

Analysis of trichlorocarbanilide and triclosan in soaps by reverse phase high pressure liquid chromatography

A method has been developed for the rapid and direct analysis of bacteriostats (3,4,4′-trichlorocarbanilide and 2,4,4′-trichIoro-2′ -hydroxydiphenyl ether) in soaps with the aid of reverse phase high pressure liquid chromatography (HPLC) The bacteriostats were conveniently analyzed by UV absorption detection at 280 nm. A typical analysis of bacteriostats by this method requires 15 min for sample preparation and 15 min for the HPLC run. As the system needs no equilibration time (isocratic elution), it is immediately and reproducibility.     

Triglyceride separation by reverse phase high performance liquid chromatography

Rapid separations of triglycerides by chain length and degree of unsaturation were made by high performance liquid chromatography (HPLC) on a C-18 μ-Bondapak column with acetonitrile-acetone solvent mixtures. For saturated triglycerides, a linear relationship was observed between the carbon number and the log of the retention volume. Each double bond present in the triglyceride decreased the retention volume to approximately that of a saturated triglyceride with two carbon atoms less. Correlations of the fatty acid composition, as determined by gas liquid chromatography (GLC) with the HPLC data, provides much additional insight about triglyceride composition. To calculate triglyceride compositions, an internal standard tripentadecanoin was added to collected fractions before analysis by GLC.     

High performance liquid chromatographic separation of sucrose fatty acid esters

The synthesis of sucrose fatty acid esters always results in complex mixtures. Two procedures for quantitative analysis of sucrose monoesters, respectively sucrose diesters, by means of high performance liquid chromatography on reversed-phase columns, are described. A mixture of methanol and water (85:15, v/v) was used for the separation of the monoesters, while methanol, ethyl acetate and water (65:25:10, v/v/v) was used for the separation of diesters. These methods gave information about the amount of monoesters and diesters in the product; the ratio between sucrose monopalmitate and sucrose monostearate, and the number of the most important structure isomers. A complete separation of all the possible diester products seemed to be impossible, due to the presence of more complex structure isomers. The described procedures can give important support during preparative work on sucrose fatty acid esters and also in the evaluation of these products for application purposes.     

Quantitative analyses of hydroxystearate isomers from hydroperoxides by high pressure liquid chromatography of autoxidized and photosensitized-oxidized fatty esters

A high pressure liquid chromatography (HPLC) method is described for the determination of the isomeric hydroxysterates from hydroperoxides of oxidized fatty esters. The samples are hydrogenated and the mixtures of hydroxystearates are concentrated by partial removal of unoxidized esters and complete removal of polar materials. Isomeric hydroxystearates are then separated on a porous microparticulate adsorption (10 μ) column and elution with 0.25% isopropyl alcohol inn-hexane is monitored at 212 nm. The 8-OH, 9-OH, 10-OH, 11-OH and 16-OH isomers were completely separated, but the 12-OH, 13-OH and 15-OH were only partly resolved by HPLC. The relative percentages of isomeric hydroxy esters were analyzed quantitatively by a computer integration method. Accuracy of the method was checked with known mixtures of synthetic hydroxystearates. The isomeric hydroperoxide composition of oxidized methyl oleate, linoleate, linolenate and soybean methyl esters determined by HPLC were in good agreement with previous analyses by gas chromatography-mass spectrometry. Presented at ISF-OACS Meeting, New York, NY, April 27–May 1, 1980.     

High pressure liquid chromatography of alpha olefin sulfonates

Alpha olefin sulfonates (AOS) are a complex mixture of the posi-tional isomers of hydroxyalkane sulfonates, alkene sulfonates, and disulfonates. This paper describes a qualitative method for separat-ing these various components by reverse-phase high pressure liquid chromatography. The column utilized was a DuPont Zorbax TMS (4.6 mm × 25 cm) with a water/methanol (25:75, v/v) mobile phase containing sodium nitrate at a concentration of 0.4M. The hydroxyalkane sulfonate and alkene sulfonate peaks were identified using laboratory prepared standards. The disulfonate peaks were located using controlled sulfonation conditions. More work needs to be done to separate an overlap of C₁₆ 3-hydroxyalkane sulfonate and C₁₄ 2-alkene sulfonate in 1416 AOS. However, if studies are based on single carbon number AOS samples, the overlap of these peaks can be avoided. This method can be utilized as a qualitative tool for the comparison of sulfonation runs, the identification of AOS within a detergent, or the identfication of the olefin type used for sulfonation.     

Fractionation of petroleum resins by normal and reverse phase liquid chromatography

Native petroleum resins from two Mexican crude oils have been fractionated using reversed phase chromatography (RPC) and adsorption chromatography normal phase chromatography (NPC). RPC with acetone/DCM and NPC with cyclohexane/DCM/acetone produced different resin fractions that were characterized by Fourier transform infrared (FT-IR) spectroscopy and gel permeation chromatography (GPC). Observable reduction in polydispersity was achieved for the resins with both systems. Chromatographic fractionation permits a more complete inventory of structural features in this kind of complex polar-hydrocarbon mixtures.     

Improved separation of conjugated fatty acid methyl esters by silver ion-high-performance liquid chromatography

Operating from one to six silver ion-high-performance liquid chromatography (Ag⁺-HPLC) columns in series progressively improved the resolution of the methyl esters of conjugated linoleic acid (CLA) isomeric mixtures from natural and commercial products. In natural products, the 8 trans, 10 cis-octadecadienoic (18∶2) acid was resolved from the more abundant 7 trans, 9 cis-18∶2, and the 10 trans, 12 cis-18∶2 was separated from the major 9 cis, 11 trans-18∶2 peak. In addition, both 11 trans, 13 cis-18∶2 and 11 cis, 13 trans-18∶2 isomers were found in natural products and were separated; the presence of the latter, 11 cis, 13 trans-18∶2, was established in commercial CLA preparations. Three Ag⁺-HPLC columns in series appeared to be the best compromise to obtain satisfactory resolution of most CLA isomers found in natural products. A single Ag⁺-HPLC column in series with one of several normal-phase columns did not improve the resolution of CLA isomers as compared to that of the former alone. The 20∶2 conjugated fatty acid isomers 11 cis, 13 trans-20∶2 and 12 trans, 14 cis-20∶2, which were synthesized by alkali isomerization from 11 cis, 14 cis-20∶2, eluted in the same region of the Ag⁺-HPLC chromatogram just before the corresponding geometric CLA isomers. Therefore, CLA isomers will require isolation based on chain length prior to Ag⁺-HPLC separation. The positions of conjugated double bonds in 20∶2 and 18∶2 isomers were established by gas chromatography-electron ionization mass spectrometry as their 4,4-dimethyloxazoline derivatives. The double-bond geometry was determined by gas chromatography-direct deposition-Fourier transform infrared spectroscopy and by the Ag⁺-HPLC relative elution order.     

Retention behavior of triglycerides on reverse phase columns using pseudophase liquid chromatography

The use of micellar mobile phases in decreasing the elution time of peanut triglycerides on 10µ reverse phase columns is demonstrated. Both cationic and anionic surfactants were used with “end-capped” and “non-end-capped” reverse phase columns. Surfactants added to both nonaqueous and aqueous organic mobile phases reduced the elution time of all triglyceride peaks when compared to a mobile phase without a surfactant modifier. Sodium dodecyl sulfate (SDS) as the modifier in the mobile phase was the most effective in reducing elution time for triglycerides when an “end-capped” column was used as the stationary medium. Increasing concentrations of surfactant in the mobile phase resulted in corresponding decreases in elution times. A unique feature of micellar phases is that any increase in concentration only alters the concentration of the micelles in the mobile phase. The objective of this study was to investigate the retention behavior of large, non-ionic solute molecules and to elucidate the adsorption mechanism on reverse phase columns.     

Determination of physicochemical properties of some fatty acid methyl esters by gas liquid chromatography

Physicochemical data such as vapor pressures (p⁰), heats of vaporization (ΔH_v), activity coefficents at infinite dilution (γ^∞) and excess partial molar entropy (ΔS _e ⁰ ) are considered important for conducting unit processes and designing reactor equipment. Scanty information regarding such data is available in the literature for the higher fatty acid methyl esters. The objective of this research was to determine the physicochemical properties of higher fatty acid methyl esters (C₁₁–C₂₃) by a gas-liquid chromatographic technique with SE-30 and diethylene glycol adipate as stationary phases. Correlations between carbon numbers and various thermodynamic properties have indicated definite trends, which could be useful in predicting the properties of unknown fatty acid methyl esters. The data generated may be useful to chemical engineers in the construction of storage tanks, solvent extractors and distillation columns. IICT communication no. 2993.     

反相高效液相色谱测定中华苦荬菜中的木犀草素

目的：建立中华苦荬菜中木犀草素含量的测定方法。方法盐析法消除植物多酚的干扰；反相高效液相色谱法测定：C18为固定相；甲醇-水-醋酸(52：47．6：0．4v／v；pH=4．0)为流动相；检测波长254nm；柱温25℃。结果：木犀草素与其它物质得到了基线分离。结论：该方法为天然植物中木犀草素的开发提供了简便、灵敏、准确的测定方法。     

全原子分子动力学模拟反相色谱分离细胞色素C的过程

采用全原子分子动力学方法模拟了反相色谱分离蛋白质的吸附和洗脱过程。采用表面键合C4烷基链的硅胶基质作为反相色谱介质和细胞色素C作为蛋白质模型,模拟蛋白质在反相色谱分离过程中的构象变化。结果显示:在吸附过程中,蛋白质在释放出表面结合水分子的同时置换出色谱介质表面的水分子。与其在溶液中的天然构象相比,吸附态蛋白质的构象发生改变。在洗脱过程中,随着溶剂从水切换到甲醇,甲醇取代水分子包覆在介质和蛋白质表面,将蛋白质从介质表面置换下来。分子模拟的结果再现了有关反相色谱"优先水化"的吸附机制,并从分子水平上展现了吸附和洗脱过程中蛋白质、色谱介质和溶剂之间相互作用,对反相色谱介质设计和过程优化提供了参考。     

High pressure phase equilibria of ethyl esters in supercritical ethane and propane

The high pressure phase equilibria of ethyl esters (ethyl decanoate/caprate, ethyl dodecanoate/laurate, ethyl tetradecanoate/myristate and ethyl hexadecanoate/palmitate) in supercritical ethane and propane have been measured in the temperature ranges 311–358 K (T_R = 1.02–1.17) and 376–409 K (T_R = 1.02–1.11), respectively. The measurements were conducted in a high pressure view cell for ethyl ester mass fractions between 0.015 and 0.65. The results show a generally linear relationship between the phase transition temperature and pressure. No temperature inversions or three phase regions were observed. An increase in hydrocarbon backbone length leads to an increase in phase transition pressure. For ethane as supercritical solvent, this increase is linear. For propane as supercritical solvent, the nature of the increase was not quantified as the magnitude of the increase would be significantly influenced by the experimental measurement error as the observed increase is not very large. Comparison of the phase behaviour of ethyl esters with methyl esters shows very little difference, yet the phase transition pressure of ethyl esters in supercritical ethane and propane is significantly lower than those of the corresponding acids. The phase transition pressure of ethyl esters in ethane and propane is also lower than those in carbon dioxide.     

Precision and accuracy in gas liquid chromatography of C14-C18 fatty methyl esters

Repetitive analyses of four primary standards for fatty methyl esters by gas liquid chromatography (GLC) with polyester columns and thermal conductivity detection established standard deviations ranging from ±0.3–0.5% corresponding to coefficients of variation of 1.0–2.0%. These data, representing a relative error of measurement of 1.5–3.0% at a 99% confidence level, suggest a precision approaching that of conventional spectrophotometric measurements. Proportionality factors, calculated from known mass or molar concentration divided by area % from GLC analysis, were found to be reproducible correction factors which may be generally applicable to GLC analysis of fatty methyl esters with polyester columns and thermal conductivity detectors. Mass response to a thermal conductivity detector was found to decrease with either increasing molecular weight for saturated C₁₄–C₁₈ fatty methyl esters or with unsaturation among the C₁₈ unsaturated esters, while molar response increases with molecular weight and decreases with degree of unsaturation. The use of uncorrected area % data can introduce significant absolute mass errors ranging from about +11% for myristic acid to −17% for linolenic acid. Presented at the AOCS Meeting, New Orleans, La., April 1964. So. Utiliz. Res. and Dev. Div., ARS, USDA.     

Supplementary consideration of the triglyceride matrix model on reverse phase high performance liquid chromatography

The matrix model that has been expressed as linear relationship between the logarithm of the relative retention time of a molecular species of a triglyceride versus total acyl carbon number or total double bonds when only one acyl group differs in carbon number or number of double bonds was reviewed. A similar linear relationship was observed when the fatty acid residues were substituted in the triglyceride molecule. This relationship was demonstrated by introducing the theory of partition chromatography presented by A.J.P. Martin.     

High performance reversed phase chromatography of cholesterol and cholesteryl esters of human plasma lipoproteins

Cholesterol and cholesteryl esters were separated according to their carbon number and number of double bonds by high performance reversed-phase chromatography (HPRC) using acetonitrile/chloroform/methanol (1∶1∶1, v/v) as a mobile phase. It was found that within the same equivalent carbon number (ECN) category, cholesterol esters with the highest number of double bonds eluted ahead of those with a lower number of double bonds, and with thecis isomers eluting ahead of theirtrans partners. Thus, cholesteryl oleate (C27-18∶1c) elutes ahead of cholesteryl palmitate (C27-16∶0) and ahead of cholesteryl elaidate (C27-18∶1t). Human lipoprotein, as well as rat liver cholesteryl esters, were separated using this technique.