Capillary GLC Research Articles

Interlaboratory evaluation of injection techniques for triglyceride analysis of cocoa butter by capillary gas chromatography

As part of two international collaborative studies, in which 14 laboratories applied capillary GLC to determine the triglyceride (TG) profile of cocoa butter, the performance of different sample introduction techniques, i.e. cold on-column injection (OCI), split injection and programmed-temperature vapouriser (PTV) injection, was compared. In both studies, the participants did not apply a uniform GLC procedure. Synthetic mixtures of triglycerides were chosen to permit an accurate determination of detector response factors. No statistically significant difference was found between the mean values obtained by different injection modes. The OCI, generally recommended as best practice, did not give superior results than the PTV or the split injection techniques.

Detailed studies on some lipids of <i>Silybum marianum</i>(L.) seed oil

Eight lipid patterns of Silybum marianum (L.) Gaertn seed oil, not hitherto reported, (20%) have been elucidated in this laboratory using capillary GLC and HPLC as main tools of analysis. The oil is rich in linoleic acid (53.3%) and oleic acid (21.3%). Five major triacylglycerols containing linoleic acyls namely LLL, LLO, LLP, LOO and LOP were detected by HPLC using FID detector, these triacylglycerols are also predominating in both cottonseed and sunflower oils but in different proportions. The total tocopherols content (260 ppm) was determined directly in the oil by HPLC. It was found that the oil contains alpha -tocopherol as a major constituent (84.5%) resembling sunflower oil. The whole sterols pattern, as determined as their trimethylsilyl derivatives by GLC, includes campesterol, 5-stigmasterol, beta-sitosterol, 7-stigmasterol, avenasterol and spinasterol. The four sterols lipid clases of free and acylated sterols and sterylglycosides have been determined as their 9- and 1- anthroylnitrile derivatives by fluorescence and UV- HPLC respectively.

Quinolizidine alkaloid profiles of two taxa of Teline maderensis.

The alkaloid composition of the aerial parts of two taxa of Teline maderensis was studied by capillary GLC and GLC-MS. N-Methylcytisine was the major alkaloid found in both plants. Contents of cytisine and lupanine were higher in T. maderensis var. paivae while anagyrine content was more pronounced in T. maderensis var. maderensis. The alkaloids dehydrocytisine, N-acetylcytisine and epibaptifoline appeared only in T. maderensis var. maderensis and N-formylcytisine was identified as a minor constituent in T. maderensis var. paivae, and detected only in trace amounts in the other variety of the plant.

Capillary GLC: a robust method to characterise the triglyceride profile of cocoa butter — results of an intercomparison study

AbstractThe results of a method intercomparison study, in which 13 laboratories applied high‐temperature capillary GLC on fused‐silica columns coated with medium‐polarity stationary phases to determine the triglyceride profile of cocoa butter, are reported. The participants did not apply a uniform GLC procedure based on a standard method, but were requested to use their own methodology. However, certain requirements relating to the separation efficiency and the accuracy, had to be fulfilled. The relative standard deviation of the reproducibility was less than 5% for the major triglyceride components of cocoa butter. The results of the present study indicate that neither the type of capillary column employed nor sample injection techniques or other chromatographic conditions influenced to a measurable degree the agreement of results between the participating laboratories. Therefore, we conclude that high‐temperature capillary GLC is a robust and reliable technique for the characterisation of cocoa butter by determining its triglyceride pattern.

Isomers of hexadecenoic and hexadecadienoic acids in Androsace septentrionalis (Primulaceae) seed oil.

Seeds of Androsace septentrionalis of the genus Androsace (tribus Primuleae) from the plant family Primulaceae were studied for their oil content and FA composition. The seed oil of A. septentrionalis was found to contain two unusual FA rarely occurring in plants: 11-cis-hexadecenoic acid (16:1delta11c or 16:1n-5) and 9-cis,12-cis-hexadecadienoic acid (16:2delta9c,12c or 16:2n-4). It also contained an unusually high amount (21.4%) of 9-cis-hexadecenoic acid (palmitoleic acid; 16:1delta9c or 16:1n-7), i.e., at a level higher than that of oleic acid, in addition to common FA. Compared with most plant seed oils, at 3.8% the level of 18:1delta11c (or 18:1n-7) also was elevated. The nonidentity of the Androsace 16:2-acid with the 16:2-acid, which is very typical for Ranunculus spp., as well as its identity with the 16:2-acid typically found in Asclepiadaceae was established by co-chromatography. The structure and composition of the constituent FA of A. septentrionalis were also determined by various chromatographic methods (TLC, Ag+-TLC, capillary GLC) and spectroscopic methods (IR, GC-MS). The significant deviation of the Androsace FA pattern from that of other Primuleae, indicating a separate phylogenetic position of Androsace, is discussed.

Trans FA in sunflower oil at different steps of refining

AbstractThe contents of total trans FA of sunflower oils at different stages of refining processes were determined by capillary GLC. The contents of 18∶1, 18∶2, and 18∶3 trans acids were 0.22±0.03, 2.31±0.23, and 0.03±0.01%, respectively, in physically refined sunflower oils, and 0.05±0.01, 0.69±0.26, and 0.02±0.01%, respectively, in chemically refined sunflower oils. The total trans FA contents drastically increased at the end of the physical refining process. The total trans FA contents of chemically refined sunflower oils were <1%. Because of the high temperature applied in the last stage of physical refining, the content of total trans FA was higher than in chemically refined sunflower oils. The last‐stage conditions should be carefully evaluated to reduce the formation of trans FA during physical refining.

Fat, fishing patterns, and health among the Bardi people of north Western Australia.

Research into the resource use strategies of the Bardi Aboriginal People of One Arm Point, Western Australia, found that they maximize the consumption of specific beneficial marine FA. The Bardi assess the relative fatness of fish and animal species in their environment, procuring fish and marine species only when they are considered to be at their fattest stage: during specific seasons; at specific physiological life stages, or through on-site evaluation. In June 1999 and September 2000, samples of fish, dugong, oyster, and turtle were collected by Bardi fishermen, focusing specifically on species considered to be high in fat content and very popular among the Bardi. Nine species were analyzed for total lipids and FA profile, which were determined by capillary GLC. Comparative lipid analysis established that the Bardi hunters' selection process between species and within species and the selection of specific fish fat deposits increase the levels of beneficial F made available to the community. Bardi fishing and hunting patterns meet a demand for fat within the community and may protect many species of fish whose spawning season is inversely related to the accumulation of the specific gut fat deposits sought by the Bardi. These fat deposits make up for the relatively low levels of fat in the flesh of tropical fish. The Bardi model provides important insights into the nature of human-environment interaction and expands our understanding of the role that warmer-water fisheries can play in human health.

Composition and Antimicrobial Activity of Essential Oil and HexaneÐEther Extract of Tanacetum santolinoides (DC.) Feinbr. and Fertig

Tanacetum santolinoides, Essential Oil Composition, n-Hexane-Ether Extract Composition The essential oil of the aerial parts of Tanacetum santolinoides was analyzed by capillary GLC and GLC-MS. Altogether 30 components were identified. The main constituents were thymol (18%), trans-thujone (17.5%), trans-chrysanthenyl acetate (13.2%), cis-chrysanthenyl acetate (9.2%), umbellulone (9.7%) and 1,8-cineole (4.7%). Similar essential oil pattern in addition to palmitic acid methyl ester, palmitic acid, stigmasterol, sitosterol and two flavonoidal aglycons were found in the n-hexane-ether extract. The oil showed strong in vitro activity against E. coli, Bacillus subtilis and Candida albicans.

Retinal sensitivity loss in third-generation n-3 PUFA-deficient rats.

A previous study conducted in guinea pigs suggested that ingestion of diets high in EPA and DHA may result in suboptimal retinal function. The aim of the present study was to evaluate retinal function in pigmented (Long-Evans) rats, raised to a third generation on diets that were either deficient in n-3 PUFA or adequate (with the addition of DHA). Electroretinographic assessment employed full-field white flash stimulation. Photoreceptor responses were evaluated in terms of peak amplitudes and implicit times (a-wave, b-wave), intensity-response functions (Naka-Rushton), and the parameters of a model of transduction (P3). Retinal phospholipid FA composition was measured by capillary GLC. DHA levels were reduced by 55% in n-3-deficient animals compared with the n-3-adequate group, whereas the levels of docosapentaenoic acid n-6 were 44 times higher in n-3-deficient animals. The level of arachidonic acid was marginally higher (12.8%) in n-6-adequate animals. The n-3-deficient animals exhibited significantly reduced retinal sensitivity (sigma and S values were both affected by 0.29 log units) and increased b-wave implicit times compared with those fed the n-3-adequate diet. These data suggest that n-3 PUFA are required for development of retinal sensitivity, more so than other indices of retinal function assessed by current methods, such as maximal response amplitude. However, the benefit for retinal function of adding preformed DHA to diets already replete in n-3 PUFA remains unclear.

Wax composition of sunflower seed oils

AbstractWaxes are natural components of sunflower oils, consisting mainly of esters of FA with fatty alcohols, that are partially removed in the winterization process during oil refining. The wax composition of sunflower seed as well as the influence of processing on the oil wax concentration was studied using capillary GLC. Sunflower oils obtained by solvent extraction from whole seed, dehulled seed, and seed hulls were analyzed and compared with commercial crude and refined oils. The main components of crude sunflower oil waxes were esters having carbon atom numbers between 36 and 48, with a high concentration in the C40−C42 fraction. Extracted oils showed higher concentrations of waxes than those obtained by pressing, especially in the higher M.W. fraction, but the wax content was not affected significantly by water degumming. The hull contribution to the sunflower oil wax content was higher than 40 wt%, resulting in 75 wt % in the crystallized fraction. The oil wax content could be reduced appreciably by hexane washing or partial dehulling of the seed. Waxes in dewaxed and refined sunflower oils were mainly constituted by esters containing fewer than 42 carbon atoms, indicating that these were mostly soluble and remained in the oil after processing.

Pyrrolizidine alkaloid profiles of some Senecio species from Egypt.

Alkaloid profiles of two Egyptian Senecio species (Senecio aegyptius var. discoideus and S. desfontainei) in addition to a cultivated species (S. cineraria) were studied using capillary GLC and GLC-mass spectrometry with respect to pyrrolizidine alkaloids (PAs). Four alkaloids were identified in S. aegyptius var. discoideus, 8 in S. desfontainei and 13 in S. cineraria. Some of these alkaloids have not been reported from these plants. The alkaloidal pattern of different plant organs (flowers, leaves, stem, root) were also investigated. Senecionine has been found to be a one of the major alkaloid in all studied species, it was isolated and its structure was elucidated by 1H- and 13C-NMR.

Chemical composition and biological activity of the essential oils of Senecio aegyptius var. discoideus Boiss.

The essential oil of Senecio aegyptius var. discoideus flowers, leaves, stems and roots were isolated by hydrodistillation. Analysis of the oils by capillary GLC and GLC-mass spectrometry were performed and 34 out of 37 compounds were identified. The main component was isolated and characterized as 1,10-epoxyfuranoeremophilane using a combination of GLC, GLC-MS, and NMR analyses. The oils of flowers, leaves and stems were rich in monoterpene hydrocarbons while the root oil mainly contains furanoeremophilanes. Flower and leaf volatile oils showed significant level of antifungal activity against C. albicans, moderate effect against Gram positive bacteria, however, it has weak activity against Gram negative bacteria. The isolated sesquiterpene (1,10-epoxyfuranoeremophilane) exhibited substantial inhibitory activity against Gram negative bacteria.

Determination of FA composition and total trans FA of Turkish margarines by capillary GLC

AbstractIn this research, FA composition and total trans FA contents of 16 different brands of margarine (8 hard‐type and 8 soft‐type) sold in Turkey were determined by capillary GLC method. According to the results, the contents of saturated FA, monounsaturated FA, and PUFA were within the ranges of 23.9–32.3, 44.0–61.9, and 14.2–24.1%, respectively, in hard‐type margarines, and 27.0–39.9, 21.0–40.9, and 32.0–53.7%, respectively, in soft‐type margarines. Hard‐type margarines contained total trans FA concentrations of 20.1–34.3%, whereas soft‐type margarines contained less than 8.9% total trans FA. C18∶1trans acid content was within the range of 18.5–29.8% in hard‐type margarines, and it was significantly higher than the range in soft margarines (0.7–8.1%). C18∶1trans acid was the major trans FA in all margarines, and C18∶3trans acid concentrations were less than 0.2%.

GLC and GLC-mS analysis of thiophene derivatives in plants and in in vitro cultures of Tagetes patula L. (Asteraceae).

The occurrence of thiophenic compounds in diverse plant organs and in in vitro root-, callus- and cell suspension cultures of Tagetes patula cv. Carmen was investigated using capillary GLC and GLC-MS. The separation of thiophenes by capillary GLC and the group specific MS fragmentation with the typical sulfur isotope peaks allowed the unequivocal assignment of individual thiophenes in complex mixtures, even when occurring in traces and in the presence of different geometrical isomers. The extracts of Tagetes patula cv. Carmen contained the following 8 thiophene compounds: 5-(3-buten-1-ynyl)-2,2'-bithienyl (BBT), 5'-methyl-5-(3-buten-1-ynyl)-2,2'-bithienyl (MeBBT), 5-(1-pentynyl)-2,2'-bithienyl (PBT), 5-(4-hydroxy-1-butynyl)-2,2'-bithienyl (BBTOH), 2,2',5,2"-terthienyl (alpha-T), 5-(4-acetoxy-1-butynyl)-2,2'-bithienyl (BBTOAc), 5-methylaceto-5'-(3-buten-1-ynyl)-2,2'-bithienyl (AcOCH2BBT), and 5-(3,4-diacetoxy-1-butynyl)-2,2'-bithienyl (BBT(OAc)2). The most complex thiophene profile, including the less common PBT was detected in aerial parts of freshly harvested plant material. Under in vitro conditions only the root cultures, but not callus or cell suspension cultures produced substantial amounts of irregular thiophenes confirming that roots are the main site of thiophene biosynthesis.

Solid Phase Extraction Method for Selective Determination of Phthalate Esters in the Aquatic Environment

The use of solid phase extraction and capillary GLC provides thebasis for the selective determination of phthalate ester plasticizers in rivers and marine water samples. Of the severalsolvent ratios (methanol in dichloromethane) used for selective elution of phthalate esters from the C18 solid phase glass catridge, the 50/50 ratio, CH3OH in CH2Cl2 (v/v)gave the best result. The method was tested on river and marinewater samples that receive effluent from industries that use phthalate esters. The rivers and marine water samples were grossly polluted as several phthalate esters, for example, dimethyl (DMP), diethyl (DEP), dibutyl (DBP) and diethylhexyl (DEHP)were present at 0.03–2306±9.4 μg L-1. A study on uncontaminated water was done to establish background levels.

Transfer of quinolizidine alkaloids from hosts to hemiparasites in two Castilleja-Lupinus associations: analysis of floral and vegetative tissues.

Many hemiparasites, including several members of the Castilleja genus (Scrophulariaceae), obtain secondary compounds from their host plants. Both Castilleja miniata in subalpine Colorado and C. indivisa in central Texas have reduced herbivory when obtaining alkaloids from the hosts Lupinus argenteus and L. texensis (Fabaceae), respectively. However, pollinators were not deterred from visiting Castilleja parasitizing alkaloid-containing hosts. To determine if alkaloids are present in all tissues of plants parasitizing lupins, we analyzed floral tissue as well as leaves of both Castilleja species. Leaves, bracts, calices, corollas, gynoecium and nectar of both Castilleja species were examined for quinolizidine alkaloid presence using a Dragendorff reagent, and alkaloids were identified in vegetative tissue and nectar by capillary GLC and GLC-MS. Lupanine and alpha-isolupanine were the principal alkaloids in C. indivisa parasitizing L. texensis, while principal alkaloids of C. miniata parasitizing L. argenteus were 5,6-iso-dehydrolupanine, alpha-isolupanine, thermopsine, and 17-oxolupanine. Except for 17-oxolupanine, which was probably synthesized by biotransformation in the parasite, all other alkaloids correspond to those present in the host plants. Alkaloids were present in the leaves of both Castilleja species, and in the bracts, calices and gynoecium of some plants, but never in the corollas. Alkaloids from L. texensis and L. argenteus were not detected in nectar of either Castilleja species. The presence of alkaloids in leaves and outer floral tissue of both Castilleja species, but not nectar, may explain why alkaloid uptake and storage affected herbivores but not pollinators.

Quinolizidine alkaloid profiles of Lupinus varius orientalis, L. albus albus, L. hartwegii, and L. densiflorus.

Alkaloid profiles of two Lupinus species growing naturally in Egypt (L. albus albus [synonym L. termis], L. varius orientalis) in addition to two New World species (L. hartwegii, L. densiflorus) which were cultivated in Egypt were studied by capillary GLC and GLC-mass spectrometry with respect to quinolizidine alkaloids. Altogether 44 quinolizidine, bipiperidyl and proto-indole alkaloids were identified; 29 in L. albus, 13 in L. varius orientalis, 15 in L. hartwegii, 6 in L. densiflorus. Some of these alkaloids were identified for the first time in these plants. The alkaloidal patterns of various plant organs (leaves, flowers, stems, roots, pods and seeds) are documented. Screening for antimicrobial activity of these plant extracts demonstrated substantial activity against Candida albicans, Aspergillus flavus and Bacillus subtilis.

Free and sulfated sterols of two far-east Leptasterias starfish

NMR spectroscopy, capillary GLC, and GLC-MS are used to study the composition of free and sulfated sterols from the far-east starfishLeptasterias alaskensis asiatica(Fischer) andL. Fisheri(Djakonov). The total free sterols of both species are shown to have similar qualitative and quantitative compositions and contain mainlyΔ7-sterols. Sterol sulfate fractions contain cholesterol sulfate as the main component but differ in the ratios ofΔ5:δ0:δ7-sterol derivatives. Possible reasons for these differences are discussed. A new steroid, 3β-hydroxycholest-5-en-7-one sulfate, was isolated.

Determination of the Positional-Species Composition of Plant Reserve Triacylglycerols by Partial Chemical Deacylation

To determine the positional-species composition (PSC) of the sunflower oil triacylglycerols (TAGs), these TAGs were separated in a native state by preparative TLC on alumina and subjected to a partial chemical deacylation with the Grignard reagent under anhydrous conditions. The rac-1,2-diacylglycerols (DAGs) formed in this reaction were identified by comparing their TLC mobilities with the respective standard separated from the products of enzymatic hydrolysis of lecithin. Subsequently, the DAGs as their borate complexes were isolated from the reaction mixture by preparative TLC on silica gel. The quantitative fatty acid composition of both the DAGs and the initial TAGs was determined by capillary GLC. The PSC of TAGs calculated from the data obtained using a computer program was consistent with the data on sunflower TAG composition reported by other researchers using an independent method. Thus, the technique developed here makes it possible to obtain reliable data on the concentration of all TAG positional species in the plant tissue.

A Comparative Study of the in vitro Antimicrobial Activity of Tea Tree Oils s.l. with Special Reference to the Activity of β-Triketones

The in vitro antibacterial and antifungal activities of Australian tea tree oil, cajuput oil, niaouli oil, kanuka oil and manuka oil as well as of a beta-triketone complex isolated from manuka oil were investigated in a constituent-oriented study. The compositions of the oils were analysed by capillary GLC and GLC-MS. The MICs for sixteen different microorganisms were determined applying the broth dilution method. Australian tea tree oil showed the best overall antimicrobial effect. The best inhibitory effects on Gram-positive bacteria and dermatophytes were achieved with manuka oil due to its beta-triketone content.