Gas chromatographie separation of cis and trans isomers of long chain amines

There are important differences in the physical properties of the cis and trans isomers of unsaturated long chain amines. Because of these differences, it is desirable to know the ratio of the cis and trans isomers. This separation can be accomplished by capillary column gas chromatography of the amine derivatives; however, the use of capillary columns is too slow for routine analysis. It was found that the cis and trans isomers of unsaturated amines can be rapidly separated on packed columns containing cyanopropyl-phenylsilicone liquid phases (Apolar 10C). The primary amines are converted to the trifluoroacetamides and separated on 6- to 10-ft columns containing 10% Apolar 10C at 180 C. The technique has been applied to unsaturated long chain primary amines and diamines. Useful information on the isomerization of these compounds during their synthesis can be obtained.     

Gas-liquid chromatographic analysis of monoglycerides as their trimethylsilyl ether derivatives

A quantitative method is described for the rapid gas-liquid chromatographic analysis of monoglycerides of long chain fatty acids as their trimethylsilyl (TMS) ether derivatives. The TMS derivatives are formed rapidly and quantitatively at room temp without isomerization. The TMS derivatives of 1- and 2-monoglycerides may be separated on polyester columns, which can also be used for the analysis of methyl esters. A mixture of the 1- and 2-isomers of monopalmitin and monoolein was quantitatively analyzed. A mixture of monocaprin, monolaurin, monomyristin, monopalmitin and monosterin was also analyzed. A mixture of 1-monostearin, 1-monoolein and 1-monolinolein was also resolved. The analyses were carried out on packed and large bore capillary columns of diethylene glycol succinate polyester (DEGS) and Apiezon L. Capillary columns that required the use of a splitter were nonquantitative, resulting from what appeared to be fractionation at the splitter. Acid conditions, including those provoked by the use of phosphoric acid stabilized polyesters, cleaved the TMS derivatives to yield the original hydroxy compound. Presented at the AOCS Meeting in New Orleans, 1964. This work is taken from a dissertation to be submitted to Texas A&M University Graduate College in partial fulfillment of the requirement for the degree of Doctor of Philosophy. Supported in part by a grant from the National Institutes of Health.     

Use of dimethylsilyl ether derivatives in gas chromatography

The results show the use of dimethylsilyl (DMS) derivatives to be valuable for: 1) decreasing retention times of samples being analyzed by gas chromatography; 2) conducting analyses at lower temperatures; 3) analyses of mixtures which cannot be separated as trimethylsilyl (TMS) derivatives; and 4) analyses of mixtures of isomers on one column as both DMS and TMS derivatives rather than using two columns with one derivative. The work reported here is only of a preliminary nature and does not include a study of the kinetics of the reaction. It is hoped that this paper will stimulate more work in this area.     

Gas chromatographic resolution of homologous monoacyl and monoalkylglycerols

Homologous series of 1 and 2 monoacyl and monoalkyl-sn-glycerols with 0–6 double bonds were resolved by gas liquid chromatography as the trimethylsilyl ethers and acetates using ethylene glycolsuccinate siloxane, cyanopropylphenylsiloxane, and methylsiloxane liquid phases. The trimethylsilyl ethers gave effective separation of positional isomers and saturated and unsaturated derivatives of acylglycerols on both ethylene glycolsuccinate siloxane and cyanopropylphenylsiloxane, columns. The corresponding acetyl esters were eluted on the basis of unsaturation, but positional isomers overlapped. The ethylene glycol-succinate siloxane and cyanopropylphenylsiloxane columns resolved the positional isomers and saturated and unsaturated species of the alkylglycerols when chromatographed as the acetates, while the corresponding trimethylsilyl ethers were separated on the basis of unsaturation only. On methylsiloxane columns essentially complete overlapping was observed among the positional isomers within each acyl and alkylglycerol series when chromatographed as the acetates. There was an effective resolution of the positional isomers of the acylglycerols as the trimethylsilyl ethers on methylsiloxane. From methylsiloxane, the alkenylglycerols were eluted earlier than the alkylglycerols of corresponding carbon numbers. These species were not separated on conventional ethylene glycol-succinate siloxane or cyanopropylphenylsiloxane columns.     

Comparison of Separations of Fatty Acids from Fish Products Using a 30-m Supelcowax-10 and a 100-m SP-2560 Column

Commercial fish oils and foods containing fish may contain trans and/or isomerized fatty acids (FA) produced during processing or as part of prepared foods. The current American Oil Chemists’ Society (AOCS) official method for marine oils (method Ce 1i-07) is based on separation by use of poly(ethylene glycol) (PEG) columns, for example Supelcowax-10 or equivalent, which do not resolve most unsaturated FA geometric isomers. Highly polar 100-m cyanopropyl siloxane (CPS) columns, for example SP-2560 and CP Sil 88 are recommended for separation of geometric FA isomers. Complementary separations were achieved by use of two different elution temperature programs with the same CPS column. This study is the first direct comparison of the separations achieved by use of 30-m Supelcowax-10 and 100-m SP-2560 columns for fatty acid methyl esters (FAME) prepared from the same fish oil and fish muscle sample. To simplify the identification of the FA in these fish samples, FA were fractionated on the basis of the number and type of double bonds by silver-ion solid-phase extraction (Ag⁺-SPE) before GC analysis. The results showed that a combination of the three GC separations was necessary to resolve and identify most of the unsaturated FA, FA isomers, and other components of fish products, for example phytanic and phytenic acids. Equivalent chain length (ECL) values of most FAME in fish were calculated from the separations achieved by use of both GC columns; the values obtained were shown to be consistent with previously reported values for the Supelcowax-10 column. ECL values were also calculated for the FA separated on the SP-2560 column. The calculated ECL values were equally valid under isothermal and temperature-programmed elution GC conditions, and were valuable for confirmation of the identity of several unsaturated FAME in the fish samples. When analyzing commercially prepared fish foods, deodorized marine oils, or foods fortified with marine oils it is strongly recommended that quantitative data acquired by use of PEG columns is complemented with data obtained from separations using highly polar CPS columns.     

Lipid composition of beef brain,beef liver,and the sea anemone: Two approaches to quantitative fractionation of complex lipid mixtures

Two new schemes for fractionation of complex lipid mixtures are presented. Their use for the study of lipids of beef brain, beef liver, and the sea anemone are described. Apparatus and techniques for working in an inert atmosphere, evaporation of solutions in the cold under nitrogen, use of infrared spectroscopy for examination of lipids and their hydrolysis products, preparation and clution of diethylaminoethyl (DEAE) cellulose and silicic acid-silicate columns and general column combinations that can be used to fractionate complex lipid mixtures are considered in detail. The first scheme, employing DEAE cellulose columns followed by thin layer and paper chromatographic examination of the fractions, was applied to liver lipids. The many components, some of them new lipids not previously detected, are clearly seen with this technique but are not seen when paper or thin layer chromatography alone or silicic acid chromatography are used. The second scheme employing DEAE for initial fractionation, followed by complete separation on silicic acid and silicic acid-silicate columns, was applied to lipids of the sea anemone and beef brain. Typical lecithin and phosphatidyl ethanolamine were isolated, but sphingomyelin was not found. A new sphingolipid, ceramide aminoethylphosphonate, with a free amino group and a direct carbon to phosphorus bond was isolated and characterized. The methods used for quantitative isolation, the infrared spectra, and the amounts of cholesterol, ceramide, cerebroside, galactosylglyceride, sulfatide, sphingomyelin, lecithin, phosphatidyl ethanolamine, phosphatidyl serine, phosphatidyl inositol, triphosphoinositide, phosphatidic acid, cardiolipin, and ganglioside of beef brain are presented. Finally, the types of lipid-nonlipid interactions disclosed by column chromatography and their potential application to biological problems are discussed.     

A method for steady-state simulation of multistage separation columns involving nonideal systems

A new algorithm is developed for steady-state simulation of multistage separation columns. The algorithm decouples the model equations into two groups. The component-material balance and summation equations are solved simultaneously by the Newton-Raphson method for temperatures and component flow rates in the inner loop. The energy-balance equations are solved in the outer loop to obtain total flow rates. The K-factor is separated into three parts, each representing separately the effect of temperature, composition and apparent volatility. This makes the analytical calculation of the partial derivatives of the K-factors in the Jacobian matrix a simple task. The stability and efficiency of the algorithm is illustrated by solving a variety of problems for distillation, absorber and reboiled absorber columns. The algorithm does not require large storage space.     

GLC and TLC analysis of isopropylidene derivatives of isomeric polyhydroxy acids derived from positional and geometrical isomers of unsaturated fatty acids

Gas-liquid chromatography (GLC) and thin-layer chromatography (TLC) were used to investigate the isomeric positional geometrical isopropylidene derivatives of nine isomeric dihydroxy esters, four isomeric methyl 9,10-12-trihydroxystearates, and eight isomeric methyl 9,10-12,13-tetrahydroxystearates prepared from unsaturated fatty acids. The isopropylidenes derived fromcis andtrans monounsaturated fatty acids were easily separated on both polar and nonpolar columns. Positional isopropylidenes derived from positional isomers of monounsaturated fatty acids were not separated on either liquid phase but were resolved by TLC. Four of the eight isomeric isopropylidenes derived from the four geometrical isomers of linoleic acid were resolved on the polar column; the other four isomers eluted as a single peak. The four isomeric isopropylidene-trifluoroacetate derivatives derived from ricinoleic and ricinelaidic acids were also resolved on the polar column. GLC analyses were carried out with liquid phases of ethylene glycol succinate methyl silicone polymer (EGSS-X) and methyl silicone polymer (SE-30) packed columns. Isopropylidenes, in addition to their applicability for the resolution of polyhydroxy acid mixtures, are particularly useful for the determination of double bond positions and geometrical configurations of fatty acids without cleavage. Under contract with the U. S. Atomic Energy Commission.     

Improved Preparation Method of Polyethylenimine-Hydroxyapatite and Its Chromatographic Properties

Previously, we developed polyethylenimine-coated hydroxyapatite as a chromatography medium. This report describes a simple, safe, productive, and improved preparation method and reports further chromatographic properties. The improved polyethylenimine-coated hydroxyapatite was prepared by use of a rotary evaporator with neither decantation, cross-linking agent, nor organic solvent. In chromatography, ovalbumin (a phosphoprotein) was separated from other proteins. Furthermore, ovalbumin derivatives or nucleotides could be separated on the basis of the number of phosphate residues. This method yielded high-quality and -quantity polyethylenimine-coated hydroxyapatite.     

Stereospecific analysis of triacyl-sn-glycerolsvia resolution of diastereomeric diacylglycerol derivatives by high-performance liquid chromatography on silica

The compositions of positionssn-1, 2 and 3 of triacylglycerols can be determined by partial hydrolysis with ethyl magnesium bromide, derivatization of the total products with (S)-(+)-1-(1-naphthyl)ethyl isocyanate and isolation of the diacyl-sn-glycerol urethane derivatives by chromatography on solid-phase extraction columns containing an octadecylsilyl phase. The diastereomericsn-1,2-and 2,3-diacylglycerol derivatives are separated by high-performance liquid chromatography on silica for determination of their fatty acids by gas chromatography. Each step in the process has been evaluated rigorously. The compositions of all three positions can be calculated with good accuracy from the analyses of these compounds and that of the total triacylglycerols. Although the 1,3-sn-diacylglycerol derivatives can also be isolated easily, they do not give reliable results for the composition of positionsn-2 because acyl migration occurs during their generation. The stereospecific analysis procedure has been applied to some plant and animal triacyl-sn-glycerols of commercial and scientific interest, containing predominantly C₁₆ and C₁₈ fatty acids,i.e. safflower, sunflower, olive and palm oils, tallow, egg and rat adipose tissue. The method is not at present suited to the analysis of more complex triacylglycerols, such as milk fat or fish oils, and problems associated with these are discussed.     

Chromatographic analysis of polyglycerols and their fatty acid esters

Polyglycerols and their fatty acid esters have been analyzed by gas-liquid chromatography (GLC) as trimethylsilyl ether derivatives. Linear diglycerols and triglycerols were isolated from commercial polyglycerols by vacuum distillation. Mono- and di-fatty acid esters were synthesized in the laboratory. Two isomers of diglycerol have been separated and identified. GLC analysis was carried out on columns packed with 3% JXR on Gas Chrom Q. Response factors for diglycerol and triglycerol relative to glycerol have been established. Commercial polyglycerol esters are shown to be mixtures of glycerol, free fatty acids, mono- and diglycerides, and mono- fatty acid esters of diglycerol and triglycerol. Separation of free polyglycerols and their esters is also demonstrated by thin-layer chromatography on Silica Gel-G containing 4.0% boric acid.     

Modern procedures for the analysis of tocopherols

The development of reliable assay methodology for the tocopherols has been an evolutionary process which has required over 40 years to reach its present state. Today the analyst has at his disposal a choice of reliable and accurate methods of analysis for the eight tocopherols now known to exist in nature. The general sequence of procedure and the precautions to be observed are described. After suitable extraction procedures and careful saponification techniques, the tocopherols in the nonsaponifiable fraction can be assayed by a variety of chromatographic procedures including paper, thin layer (TLC), column and gas liquid chromatography (GLC). The current methodology of these procedures is reviewed in some detail with special emphasis on the more frequently used TLC and GLC techniques. The earlier methods of GLC assay separated only the mono-, di- and trimethylated tocopherols but methods are now available which provide separation of all the tocopherols. These developments were made possible by better columns and the use of derivatives of tocopherols. In addition to good separation, the GLC method is the most sensitive available for the quantitation of the tocopherols. Spectrophotometric measurements based on Emmerie Engel type reactions have been most frequently used for the final quantitative analysis of the tocopherols separated by paper, TLC, or column chromatography. One of six papers being published from the “Chemistry and Biochemistry of Tocopherols,” presented at the ISF-AOCS World Congress, Chicago, September 1970.     

Untersuchung von Steringemischen IV: Das Retentionsverhalten freier Sterine bei der Gas-Chromatographie

Studies on Sterol Mixtures IV: Retention Behaviour of Free Sterols in Gas Chromatography Retention behaviour of a number of free sterols was studied by gas chromatography using SE-30, UCCW-982, OV-17 and OV-25 as stationary phases. In a similar manner as tested for steryl acetates, the separation factors were determined for sterol pairs which differ by one constitutional characteristic. The efficiency of separation of the stationary phases OV-17 and OV-25 were found to be distinctly superior to those of less polar phases. Sterols having Δ²⁴(²⁵)-double bonds are especially well separated from their saturated counterparts. Steryl acetates exhibit on all four stationary phases longer retention times compared to free sterols whereas the trimethylsilyl ether derivatives show on SE-30 and UCCW-982 columns longer and in OV-17 and OV-25 columns greatly reduced retention times.     

Degradative reactions of decadienoate esters

Methyl and ethyl esters of decadienoic acid, which are normal constituents of the Bartlett pear, react with oxygen in the presence of light to produce n-hexanal, and the methyl or ethyl 4-oxybutenoate. The products were separated by gas chromatography, and identified by melting points, infrared spectroscopy, and/or the formation of derivatives. Possible reaction mechanisms are discussed. Parts of this paper are from a thesis submitted by D. E. Heinz in partial satisfaction of the requirements for the PhD degree in Agricultural Chemistry.     

Gas-liquid chromatographic analysis of mono-and diglycerides

A method is described for the quantitative analysis of mono- and diglycerides by GLC as their trimethylsilyl derivatives. Glyceryl mono and di-esters of myristic, palmitic, stearic, and oleic acids are separated by GLC on stainless steel columns, packed with 3% JXR on Gas Chrom Q. Relative response factors for monoglycerides and diglycerides have been calculated. Analyses of control and commercial mixtures with recoveries of 96 to 101% are reported.     

硫三碳菁红外染料的光谱增感及超增感技术的应用研究

红外染料自减感的化学过程是致使红外增感效率低的原因。据此 ,红外感光材料的超增感过程应与抑制染料自发减感是密切相关的。二苯乙烯类衍生物 ,以及抗坏血酸作为红外染料超增感剂 ,有效地提高红外染料的光谱增感效率。     

Studies on selective adsorption resins. XXXIII. Behavior of macroreticular chelating resins containing phosphinic and/or phosphonic acid groups in the adsorption of trivalent lanthanides

The effect of the crosslinking and the porosity of the chelating resins containing phosphinic and/or phosphonic acid groups (RSP and RCSP) on uptake of trivalent lanthanides was studied; RSP and RCSP were prepared by hydrolysis of condensation products of phosphorus trichloride with styrene–divinylbenzene copolymer beads (RS) and with chloromethylated RS, respectively. From a series of RSs synthesized by systematically changing the amount of the crosslinker (divinylbenzene) or the porogen (2,2,4-trimethylpentane), RSPs and RCSPs with different degrees of crosslinking and with different porosities were derived. Measurements of their uptake of La(III), Gd(III), or Yb(III) have clarified that RSP and RCSP with moderately crosslinked highly porous structures exhibit high capacities toward the lanthanides. Using these optimized RSP and RCSP and their respective oxidized derivatives RSPO and RCSPO, the distribution of all lanthanides (III) except for Pm(III) from aqueous hydrochloric acid solutions (0.1–1M) was examined. The distribution of each lanthanide(III) at a given concentration of the acid increases in the order RCSPO ≈ RCSP < RSPO < RSP. Their lanthanide selectivity patterns resemble one another; the selectivity increases with increasing the atomic number of the lanthanides except for the elements from Sm to Ho. In order to illustrate usefulness of these resins in the separation of lanthanides, the chromatographic separation of La(III), Nd(III), and Sm(III) was conducted using columns packed with RCSP. The three lanthanides were successfully separated by the elution with 0.5M hydrochloric acid solution without use of any organic complexing reagents, such as EDTA. © 1994 John Wiley & Sons, Inc.     

Gas-liquid chromatography of lipids,carbohydrates and amino acids

Gas-liquid chromatography is primarily a powerful separating tool. Compounds can be trapped as they emerge from the GLC apparatus for analysis by mass spectrometry and infrared or ultraviolet spectrophotometry, or the emerging separated components may flow directly into one of these instruments making positive identification of the components possible. Quantitative analyses of fats and oils are possible when certain requirements are observed. A combination of fatty acid, triglyceride and sterol analyses offers promise of a rapid means for the identification of fats and oils and their admixture or adulteration. Progress has been made on the preparation of derivatives of carbohydrates and amino acids such that these compounds may soon be analyzed as readily by GLC as lipids are today. Presented at the AOCS-AACC Joint Meeting, Washington, D.C., April 1968. E. Utiliz. Res. Dev. Div., ARS, USDA.     

Trennung von Triglyceriden nach Kettenlänge und Sättigungsgrad durch HPLC

Separation of Triglycerides According to Chain Length and Degree of Saturation by HPLC In routine fat analysis HPLC is efficiently used. For constant work columns with chemically bound C₁₈-groups are especially suitable. There are critical pairs of fatty acid-methylesters which however can be separated by means of elution agents basing on acetonitril. Oleic acid and elaidic acid can be separated by this way, too. By GLC triglycerides can only be separated according to the number ob C-atoms, whereas in HPLC double bounds have a great influence on the retention time, too. This is especially evident if elution agents, basing on nitrils, are used. The separation principle was determined by capillar gas chromatographic analysis of the HPLC fractions. Further on hints are given to avoid technical difficulties in the use of differential refractometers.     

The application of gas-liquid chromatography to the determination of vitamins E and K

The separation and quantitation of vitamins E and K wave been made possible by gas-liquid chromatography, using a mixture of two different silicone rubber polymers as the liquid stationary phase. α-Tocopherolquinone and α-Tocopherolhydroquinone could be separated from the original α-tocopherol by this technique. Crude lipid extracts from mammalian tissues contain an unknown component which converts α-tocopherolquinone to α-tocopherol during chromatography. The implications of this observation is discussed in the light of biological processes. A group of derivatives, with the trimethylsilyl ether link was prepared and characterized by gas chromatography and infrared spectrophotometry. Presented at the AOCS meeting in Toronto, Canada, 1962.