Gas-liquid chromatographic properties of positional isomers of methyl thia, selena, and tellura laurate analogs

Gas-liquid chromatographic analyses of three complete series of synthetic positional isomers of methyl thia, selena, and tellura laurate analogs were carried on a nonpolar (SE-30) and a polar (SP-2330) stationary phase. The average ECL (equivalent chain length) values of the thia, selena, and tellura laurate on SE-30 stationary phase were 13.8, 14,8, and 15.7, respectively, while on SP-2330 the average values for the same series were 17.1, 19.0, and 19.1, respectively. Positional isomers with the heteroatom at the 2-position exhibited the lowest ECL values, while those with the heteroatom at the ω-1 position gave the highes ECL values and were readily separated from the other positional isomers of the same series of analogs by this technique.     

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.     

A satisfactory glc column for the determination of epoxyoleic acid in seed oils

A number of stationary phases were evaluated for their suitability for the analysis of methyl epoxyoleate. Ethylene glycol succinate polyester, Carbowax 20M and Apiezon 舠L螇 all showed evidence of decomposition or alteration of the compound and also a loss of area on the chromatogram. A silicone rubber (SE-30) column did not exhibit this tendency and was found satisfactory for the determination of methyl epoxyoleate. A limitation of the use of an SE-30 column in the analysis of mixed esters is its inability to separate effectively fatty acid esters of the same chain length. However, by chromatographing the sample on a polyester column as well as on an SE-30 column, all of the fatty acid components of the oil can be determined quantitatively.     

Improved gas chromatographic analysis of fatty and resin acid mixtures with special reference to tall oil

A gas liquid chromatography system for the analysis of complex mixtures of fatty and resin acids has been developed. On 30–40 m long, 0.3 mm ID glass capillary columns coated with 1,4-butanediol succinate (BDS) and attaining over 90,000 effective theoretical plates, all main fatty and resin acids in wood extractives and various tall oil products can be separated and quantitatively determined without need of any prefractionation of the acids. Also the levopimaric acid is well separated. Retention values, including their temperature dependence, on columns coated with BDS or SE-30 are given for 49 significant fatty and resin acids. Applications on wood extractives, sulfate soaps, and crude and distilled tall oil are presented and discussed.     

Characterization of unsaturated fatty acids by gas-liquid chromatography

The equivalent chain length (ECL) has been determined on 79 methyl esters of unsaturated fatty acids and on 7 ethyl esters by gas chromatography. Ethylene glycol succinate (EGS), diethylene glycol succinate, β-cyclodextrin acetate and Apiezon L were chosen as the liquid phases to be used. For methyl esters of mono- and polyenoic acids, the differences between ECL on EGS and ECL on Apiezon L approximate 0.84 per double bond. For positional isomers, the ECL on both EGS and Apiezon L are usually greater for the isomer having the longer proximal end of the molecule (smallest ω value). In these terms a triple bond is approximately equal to three double bonds. Esters of nonconjugated dienoic and trienoic acids of the same chain length are not separable on Apiezon L if their proximal structures are the same. This also applies to tetraenoic and pentaenoic acids of the same chain length and the same proximal structure. Conjugation of double bonds, either with the ester carbonyl group or with themselves, yields ECL values on Apiezon L greater than the number of carbon atoms in the acid. Monounsaturated and nonconjugated polyunsaturated esters have ECL values on Apiezon L lower than the number of carbon atoms of the acid. The ECL values of ethyl esters of 18 and 20 carbon acids are greater than the corresponding methyl esters on Apiezon L. Presented at the Chicago meeting of the American Oil Chemists’ Society, Oct. 13, 1964.     

Effect of temperature on the separation of some Δ9-cis-trans isomers of methyl esters of fatty acids by open tubular gas chromatography

The influence of temperature on the gas chromatographic separation ofcis-trans isomers of the methyl esters of some monounsaturated fatty acids was studied on capillary columns coated with Apiezon L, BDS and DEGS. As far as methyl oleate and methyl elaidate are concerned, the separation is better at lower temperatures on Apiezon L (180–210 C) and at higher temperatures on polyester phases (BDS, DEGS; 150–180 C). The influence of temperature on the separation ofcis-trans isomers on the three stationary phases under study is explained by the higher values of δECL/δt forcis isomers. The variation of the equivalent carbon chain length with temperature can be used for the identification ofcis-trans isomers in natural mixtures.     

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.     

Analysis of conjugated octadecatrienoic acids inmomordica balsamina seed oil by GLC and13C NMR Spectroscopy

Separation of conjugated octadecatrienoic acids by open tubular gas liquid chromatography (GLC) was performed using glass capillary columns coated with Carbowax 20 M and with OV-1. The equivalent chain length of geometrical isomers of the conjugated octadecatrienoic acids belonging to the two series C_18:3Δ^8.10.12 and C_18:3Δ^9.11.13 were determined. The application of these results to the study of theMomordica balsamina seed oil shows that this oil contains two conjugated octadecatrienoic fatty acids in appreciable amounts, punicic acid (50%) and α-eleostearic acid (13%). The isomerization of conjugated acids inM. balsamina seed oil was followed for one year. Quantitation of octadecatrienoic acids using GLC gave results similar to those obtained with¹³C NMR.     

The preparation,gas liquid chromatography,and some physical and chemical properties of certain higher aliphatic 2,4-diketones—A new lipid class

Fourteen saturated aliphatic 2,4-diketones, ranging in chain length from C₇ to C₂₅, and one unsaturated compound, Δ¹²-2,4-heneicosenedione, were prepared by Claisen acylations of the appropriate methyl ketones, and their gas chromatographic behavior was studied. Mixtures of these diketones were resolved on columns containing UCW98 or Carbowax 20M stationary phases. Their methoxime and 2,4-dinitrophenylsemicarbazone derivatives were resolved on OV-17 and OV-1 stationary phases, respectively. Since higher homologous aliphatic 2,4-diketones have been found in mammalian tissues, they constitute a new lipid class. Deceased.     

Quantitative analysis of fatty acids and sterols in Malagasy rice bran oils

The fatty acid and sterol compositions of six Malagasy rice bran oils were evaluated. Investigation by gas liquid chromatography (GLC) using Carbowax 20 M revealed 10 fatty acids, mainly palmitic (16–20%) oleic (41–44%) and linolenic (31–37%) acids. An OV 17 column was used to separate eight sterols, mainly Β-sitosterol (53–59%), campesterol (16–26%) and stigmasterol (10–13%). No significant variation for the fatty acid and sterol contents was observed among the rice varieties studied.     

Milk fat structure of a patient with type 1 hyperlipidemia

Structural analyses were performed on milk fat samples obtained 3–10 days postpartum from a lactating patient with primary Type 1 hyperlipidemia. The milk triacylglycerols contained 3–7% C₁₀, 14–21% C₁₂, 20–30% C₁₄, 22–26% C₁₆ and 20–30% C₁₈ (largely oleic) acids. Gas liquid chromatographic (GLC) analyses of the X-1,3- and X-1,2-diacylglycerols on polar siloxane columns showed a markedly non-random association of acyl chains. Stereospecific analyses indicated that the short chain length fatty acids were confined essentially to the sn-3-position of the triacylglycerol molecule. Furthermore, these acids were largely absent from the phosphatidylcholines and the endogenous sn-1,2-diacylglycerols of the milk fat. It is concluded that the short chain fatty acids are incorporated into the milk triacylglycerols during the final stage of biosynthesis via the phosphatidic acid pathway, and that the overall fatty acid distribution is consistent with the 1-random 2-random 3-random hypothesis.     

Equivalent chain lengths of methyl octadecadienoates and octadecatrienoates

Equivalent chain lengths (ECL) have been determined for a number of methyl octadecadienoates and octadecatrienoates with different stationary phases, including Apiezon L, polyphenyl ether, diethylene glycol succinate, XF 1150, 100% cyanoethyl silicone and tetracyanoethylated pentaerythritol. ECL values for unconjugated esters are slightly larger than calculated by adding the ECL increments over stearate found for octadecenoates with the same position and configuration of double bonds. In general, differences are greater for methylene-interrupted double bonds and fortrans double bonds. They are greater for more polar columns. Average corrections can be added so that calculated ECL values agree well with the determined values. ECL increases with polarity of the stationary phase. The relative ECL pattern on different stationary phases changes little with position of double bonds in the isomers, but it is affected by double bond configuration. For esters with the same double bond positions isomers withtrans double bonds tend to have lower ECL values thancis on polar stationary phases and higher ECL values on nonpolar. ECL’s of conjugated octadecadienoates are always higher than unconjugated and increase in the ordercis,cis; mono-trans; andtrans,trans. Presented at the AOCS Meeting, Chicago, September 1970.     

Cyclopropenoid Fatty Acids in Malagasy baobab: Adansonia grandidieri (Bombacaceae) Seed Oil

Adansonia grandidieri (bombacaceae family) seed oil gives a positive Halphen test. Composition analysis of derivatized fatty acid methyl esters, in presence of silver nitrate in anhydrous methanol, after chromatography fractionation on silicagel column, were made by gas-liquid chromatography (GLC) using a packed DEGS column. Presence of malvalic and sterculic acids were detected. GLC analysis using glass capillary columns coated with Carbowax 20 M and BDS shows that A. grandidieri seed oil contains mainly palmitic (41%), oleic (22%) and linoleic (12%) acids. Cyclopropenic fatty acid concentration was 14% with 6% for malvalic and 8% for sterculic acids. A slight proportion of dihydrosterculic acid (1.5%) was observed. GLC fatty acid methyl esters analysis, without derivatization, on the two glass capillary columns coated with Carbowax 20 M and BDS gave the same results for cyclopropenic acids content.     

Characteristics and Fatty Acid Composition of Almond Tegument Oil — Comparison with Almond Kernel Oil

The total crude fat on dry basis of almond tegumet was about 14% by weight. Chemical and physical characteristics of this oil were determined. The content of unsaponifiable matter, 3.75%, was high. The percentage of saturated acids was 10.32%. The high content of essential fatty acids, 40.34% of linoleic and 1.28% of linolenic should be pointed out. Experimental results corresponding to tegument and kernel oils were compared. Gas chromatographic retention indices of fatty acids methyl esters on Carbowax 20-M, DEGS and SE-30 were determined with analitical purposes.     

Glass capillary gas chromatography-mass spectrometry of wax esters,steryl esters and triacylglycerols

Complex mixtures of wax esters, steryl esters and triacylglycerols isolated from representative biological and geochemical samples have been analyzed using combined high resolution gas chromatography and electron impact and chemical ionization quadrupole mass spectrometry. These low volatility neutral lipids containing up to 65 carbons were chromatographed intact on 15–20 m high-temperature (upper limit: 370 C) persilylated SE-52 and SE-30 glass capillary columns. Discrimination effects due to adsorptive losses and degradation were minimized using a nonvaporizing on-column injector and a direct all-glass capillary connection (370 C) to the quadrupole mass spectrometer. Structural information regarding the fatty acid and alcohol moieties was found to be maximal for methane-CI spectra in the case of wax and steryl esters, whereas EI spectra were most useful in interpreting triacylglycerol structures. Principal features of the EI and CI fragmentation patterns are discussed. The molecular composition of complex mixtures of these lipids is reconstructed for selected samples.     

Application of methoxy-bromomercuri-adduct fractionation to the analysis of fatty acids of partially hydrogenated marine oils

The fatty acids of a refined and of a partially hydrogenated menhaden oil, iodine value (IV) 84.5, were separated into different classes (e.g., monoene, diene, including pentaene and hexaene) by thin layer chromatography (TLC) of their methoxy-bromomercuri-adducts (MBM). In the solvent system hexane: dioxane, the separation of fatty acids occurred according to the degree of unsaturation. No influence was exerted by either the geometry or the position of the ethylenic bonds. The effect of the various chain lengths (C₁₄−C₂₂) was to broaden the bands, but no overlap occurred among the chain lengths. A wide range of C₂₀ unsaturated fatty acids were prepared by the hydrazine reduction of 20∶5-Δ5,8,11,14,17. These were separated into groups as MBM adducts and identified by comparison of their experimental and calculated equivalent chain lengths (ECL) in gas liquid chromatography (GLC) on SILAR-5CP and SILAR-7CP columns. This confirmed that GLC did not totally separate all groups of isomers of different degrees of unsaturation. The quantitative analysis of both refined and partially hydrogenated (IV-84.5) menhaden oils by GLC was effected by the recovery of the fatty acid methyl esters from the MBM adduct TLC bands with the addition of methyl heptadecanoate (17∶0) as an internal standard, followed by analysis of the different fractions on open-tubular columns coated with SILAR-5CP. For methylene- and nonmethylene-interrupted unsaturated acids, 100% recovery from the MBM adducts was achieved, but in the case of the conjugated dienes the maximal recovery was 70%.     

Fatty acid composition of seed oils from sixAdansonia species with particular reference to cyclopropane and cyclopropene acids

The oil content of sixAdansonia species (Bombacaceae family) of Madagascar (Adansonia grandidieri, A. za, A. digitata, A. fony, A. madagascariensis andA. suarenzensis) and Africa (A. digitata) ranges from 8 to 46%. All the oils give a positive response to the Halphen test. Malvalic, sterculic and dihydrosterculic acids were detected using gas liquid chromatography-mass spectrometry (GLC-MS). Epoxy or hydroxy fatty acids were not found in these oils. Fatty acid composition was determined by GLC using glass capillary columns coated with BDS and Carbowax 20 M. Results obtained for cyclopropenic fatty acids (CPEFA) were compared to those given by glass capillary GLC after derivatization with silver nitrate in methanol, by hydrogen bromide titration and by proton magnetic resonance (PMR). Good agreement was observed for the results given by the various methods. Malvalic acid content ranges from 3 to 28%, sterculic acid from 1 to 8% and dihydrosterculic acid from 1.5 to 5.1%. Odd-numbered fatty acids (Pentadecanoic and hepatadecanoic) were also observed in minute amounts (0.1–1.1%). Among the normal fatty acids, we observed mainly palmitic (21–46%), oleic (15–40%) and linoleic (12–32%). The relationship between fatty acid composition andAdansonia species is discussed.     

GC Separation of <Emphasis Type="Italic">cis</Emphasis>-Eicosenoic Acid Positional Isomers on an Ionic Liquid SLB-IL100 Stationary Phase

Gas chromatography (GC) of cis-eicosenoic acid (20:1) positional isomers has been investigated on a capillary column of ionic liquid 1,9-di(3-vinyl-imidazolium)nonane bis(trifluoromethyl)sulfonylimidate stationary phase (SLB-IL100). A test mixture of isomeric 20:1 methyl esters was prepared from flathead flounder flesh lipids. On a 60-m column operated at 150–180 °C, six peaks appeared in the elution order of 20:ln-15 → 20:ln-13 → 20:ln-11 → 20:ln-9 → 20:ln-7 → 20:ln-5. These peaks were baseline resolved within 20 min at 180 °C. The 20:ln-13 and 20:ln-11 isomers, poorly resolved on conventional polar polysiloxane stationary phases, were completely separated from each other with separation factor α = 1.02 and peak resolution (Rs) ≥ 1.57. When equivalent chain length (ECL) values were compared between the SLB-IL100 and CP-Sil 88 (biscyanopropyl polysiloxane), those of 20:ln-15 and 20:ln-13 exceptionally tended to be lower on the SLB-IL100. The excellent separation of 20:1 isomers seems due to less retention of 20:ln-15 and 20:ln-13 on SLB-IL100 rather than simply due to its high polarity. Analysis of herring oil 20:1 revealed the occurrence of 20:ln-13 in the Pacific herring but not in the Atlantic herring. The ionic liquid stationary phase, SLB-IL100, is effective for analyzing 20:1 isomers occurring in fish and other natural oils.     

The Conversion of 2,4-Dinitrophenylhydrazine derivatives of monocarbonyls to ethylenethioacetals and ethylenethioketals for analysis by gas liquid chromatography

A method was developed for the direct conversion of 2,4-dinitrophenylhydrazones (2,4-DNPHS) ofn-al-kanals and methylketones int ethylenethioacetals and ethylenethioketals for analysis by gas liquid chromatography (GLC). the method depended on heating the 2,4-DNPHS and 1,2-ethanedithiol with boron fluoride (BF₃) ethyl ether at 125 C for 12 min or withp-toluenesulfonic acid at 200 C for 15 min. The reaction was extracted with pentane, and after evaporation, the product was dissolved ono-cylene and injected into the GLC. High yields of above 90% were obtained from long chain 2,4-DNPHS and somewhat lower yields of about 80% were obtained from short chain 2,4-DNPHS. Eight standard ethylenethioacetals and ethylenethioketals were synthesized; their elemental analysis, bp, mp, and retention times on FFAP and SE-30 GLC columns were determined.     

Analysis of Alkylbenzenes by Capillary Gas Chromatography

Suitable operating conditions are shown for GC separation of linear alkylbenzene (AB) samples on capillary columns. Retention data on SE-30 of n-phenylalkanes C₉-C₁₆ were measured and separation factors for n-phenylalkanes isomers were calculated. For quantitative evaluation from peaks areas of n-phenylalkanes, correction coefficients were calculated. By statistical evaluation of errors, standard deviations and further statistical parameters were calculated, showing GC method as sufficiently accurate and reliable. From results of collaborative testing of the GC procedure for quantitative AB analysis, some recommendations followed, esp. for application of capillary columns with apolar thermostable stationary phase only, with advantage under temperature programming, applying reduced sample volume at limited FID attenuation. It must be pointed out, this method is strictly limited for linear AB.