Eberhard Lorbeer

Simultaneous determination of glycerol, and mono-, di- and triglycerides in vegetable oil methyl esters by capillary gas chromatography

Abstract A gas chromatographic procedure for the simultaneous determination of glycerol, mono-, di- and triglycerides in vegetable oil methyl esters has been developed. Quantitative information about this group of organic contaminants is very important for the quality of these oleochemical products when used as automotive diesel fuel substitutes. Trimethylsilylation of glycerol, mono- and diglycerides, followed by GC using a 10-m capillary column coated with a 0.1-μm film of DB-5 allows the determination of all analytes in a single GC run. Calibration is performed by analysis of standard solutions containing glycerol, mono-, di- and triolein as well as two internal standards, 1,2,4-butanetriol and tricaprin. The recovery of the procedure at different concentration levels and the repeatability of the quantitative results are evaluated.

Determination of tocopherols and sterols in vegetable oils by solid-phase extraction and subsequent capillary gas chromatographic analysis.

In general, analyses of tocopherols and sterols are performed separately in vegetable oils. By applying solid-phase extraction (SPE) prior to capillary gas chromatography, a simple and reliable procedure for the quantification of both tocopherols and sterols in a single analytical run has been developed. SPE was used as sample clean up procedure for the separation of these minor components from the triacylglycerol matrix, replacing time consuming saponification or on-line LC-GC. The analysis of tocopherols and free sterols in five different vegetable oils illustrates robustness and reliability of this method outlined. Quantification of the analytes was performed by external calibration with reference substances and internal standardization. The recovery of the procedure as well as the repeatability of the quantitative results have been evaluated.

Investigation of combwax of honeybees with high-temperature gas chromatography and high-temperature gas chromatography-chemical ionization mass spectrometry. II : High-temperature gas chromatography-chemical ionization mass spectrometry

Crude combwax of six various honey bee species have been analyzed by high-temperature gas chromatography (HTGC)-chemical ionization mass spectrometry after a two-step silylation procedure. An optimized chromatographic procedure, described previously, enables the separation of high-molecular mass lipid compounds resulting in a characteristic fingerprint of the combwaxes of different honeybee species. The coupling of HTGC to mass spectrometry requires appropriate instrumentation in order to achieve sufficient sensitivity at high elution temperatures and avoid loss of chromatographic resolution. Chemical ionization was carried out using methane as reagent gas in order to determine the molecular mass of the individual compounds by means of abundant quasi molecular ions. To confirm the presence of unsaturated wax esters, ammonia was used as reagent gas. More than 80 lipid constituents were separated and characterized by their mass spectra. Representative chemical ionization mass spectra of individual compounds are presented. Both, HTGC-flame ionization detection data and the results of the HTGC-mass spectrometric investigations enabled a rapid profiling of the individual classes of compounds in crude combwaxes.

Investigation of combwax of honeybees with high-temperature gas chromatography and high-temperature gas chromatography-chemical ionization mass spectrometry. I. High-temperature gas chromatography.

The combwaxes of the honeybee species Apis mellifera, Apis cerana, Apis dorsata, Apis laboriosa, Apis florea and Apis andreniformis have been examined by high-temperature gas chromatography. Combwax consists of a complex mixture of homologous neutral lipids. These compounds containing up to 64 carbons were chromatographed intact on a 10 m x 0.2 mm high-temperature stable SOP-50-PFD (50%-diphenyl/50%-1H,1H,2H,2H-perfluorodecylmethylpolysiloxane)-co ated Duran glass capillary column. The use of this stationary phase results in lower retention values and, at last, in lower thermal stress of the analytes. In order to minimize the discrimination effect due to adsorption and/or degradation, a two-step derivatization was performed resulting in the formation of tert.-butyldimethylsilyl esters of the long chain fatty acids and trimethylsilyl ethers of complex hydroxyesters, respectively. The derivatization procedure was optimized using a modification of the extended Donike test. In addition this test allows the quantification of the thermal stability of the derivatives performed. The derivatization procedure was applied for combwax analysis. More than 80 compounds were separated and their peak areas semiquantitatively exploited.

Effects of straw, vegetable oil and whey on physical and microbiological properties of a chernozem

Abstract A soil microcosm study was carried out to compare the effects of straw, vegetable oil or whey additions on physical and microbiological properties of a chernozem after 18 weeks of incubation. The application rates of the different organic materials were based on the addition of carbon at a concentration equivalent to 1% of soil dry mass. Straw, vegetable oil and whey additions to soil increased dry aggregate size distribution during incubation. All organic treatments had significantly higher mean weight diameter (MWD) of dry aggregates than the untreated control. The ability of whey, straw and oil to increase MWD did not differ significantly. Only straw addition significantly increased soil maximum water-holding capacity after 126 days of incubation. In comparison with the untreated control, straw tended to reduce the resistance of aggregates to abrasion, while addition of whey and vegetable oil seemed to have a positive effect on this property. Aggregates of organic matter amended soil materials had higher resistance to the dispersive action of water than those of the untreated control. Whey and straw additions sustained higher soil biomass-C contents and C mic / C org ratios than vegetable oil. Biomass development was most favored by whey addition. Fungal contributions to biomass-C dominated over bacterial contributions in whey and straw-amended soil. The opposite was observed for the oil treatment. Increases in MWD of dry aggregates seem to be related to the synthesis of biomass and soil binding metabolites in whey and straw-treated soil. Among the organic treatments, oil-amended soil had the highest respiratory activity and the lowest biomass content. Stabilizing agents derived from the microbial metabolism using oily substrate are discussed.

The fatty acid profiles - including petroselinic and cis-vaccenic acid - of different Umbelliferae seed oils

Different varieties of fennel, caraway, and coriander (3 fennel, 7 caraway, and 4 coriander varieties), which belong to the Umbelliferae family, were analyzed on oil and water content, subsequently the fatty acid profiles of the oils were determined by automated gas chromatography. Using fatty acid butyl esters a complete fatty acid profile including petroselinic and cis-vaccenic acid was obtained. Furthermore, the obtained fatty acid contents were compared to those cited in literature, which were determined using different analysis procedures. Das Fettsauremuster einschlieslich Petroselin- und cis-Vaccensaure aus verschiedenen Samen der Umbelliferae Aus der Familie der Doldengewachse wurden unterschiedliche Sorten von Fenchel, Kummel und Koriander (3 Fenchelsorten, 7 Kummel- und 4 Koriandersorten) auf ihren Ol- und Wassergehalt untersucht. Das Fettsauremuster der Ole wurde mittels automatisierter Kapillar-Gaschromatographie bestimmt. Durch die Derivatisierung der Triglyceride zu Fettsaurebutylestern konnte das vollstandige Fettsaurespektrum einschlieslich der Petroselin- und der cis-Vaccensaure ermittelt werden. Die Daten wurden mit Literaturwerten, die durch unterschiedliche Bestimmungsmethoden erhalten wurden, verglichen.

Isolation and Characterization of Wax Esters in Fennel and Caraway Seed Oils by SPE-GC

Summary A rapid method for the isolation and quantitative determination of wax esters in vegetable oils was developed. For the first time wax esters in oils were separated from the triglyceride matrix by means of solid-phase extraction, which allows rapid sample preparation in parallel and therefore a high sample throughput. The thus obtained wax ester fractions of fennel and caraway seed oils were analyzed by high temperature gas chromatography. GC-MS analyses were carried out using electron impact ionization in order to characterize the wax ester fraction. With respect to the results of the GC-MS analyses different isomers of saturated wax esters with the same carbon number were observed. Additional monounsaturated wax esters with an unsaturated fatty acid moiety were identified.

On-line liquid chromatography—gas chromatography for the analysis of free and esterified sterols in vegetable oil methyl esters used as diesel fuel substitutes

Abstract An on-line LC—GC method for the analysis of free and esterified sterols in vegetable oil methyl esters has been set up. Qualitative and quantitative information about this important group of minor components is provided without saponification and off-line pre-separation. Prior to analysis the free sterols are silylated with N-methyl-N-trimethylsilyltrifluoroacetamide; betulinol is used as an internal standard. Using concurrent eluent evaporation with the loop-type interface for eluent transfer, transfer temperature and transfer efficiency are carefully optimized. The concentration of the free sterols as well as their qualitative and quantitative composition and the concentration of the sterol esters are determined in five different types of vegetable oil methyl esters. The recovery of the LC—GC procedure and the reproducibility of the quantitative results are evaluated.

Abandoning Aggression but Maintaining Self-Nonself Discrimination as a First Stage in Ant Supercolony Formation

An ant supercolony is a very large entity with very many queens. Although normal colonies of small extent and few queens remain distinct, a supercolony is integrated harmoniously over a large area [1, 2]. The lack of aggression is advantageous: Aggression is costly, involving direct and indirect losses and recognition errors [3, 4]. Indeed, supercolonial ants are among the ecologically most successful organisms [5-7]. But how supercolonies arise remains mysterious [1, 2, 8]. Suggestions include that reduced within-colony relatedness or reduced self-nonself discrimination would foster supercolony formation [1, 2, 5, 7, 9-12]. However, one risks confusing correlation and causality in deducing the evolution from distinct colonies to supercolonies when observing established supercolonies. It might help to follow up observations of another lack of aggression, that between single-queened colonies in some ant species. We show that the single-queened Lasius austriacus lacks aggression between colonies and occasionally integrates workers across colonies but maintains high within-colony relatedness and self-nonself discrimination. Provided that the ecological framework permits, reduced aggression might prove adaptive for any ant colony irrespective of within-colony relatedness. Abandoning aggression while maintaining discrimination might be a first stage in supercolony formation. This adds to the emphasis of ecology as central to the evolution of cooperation in general [13].

Zur Identifizierung flüchtiger Substanzen aus biologischem Material mit Hilfe der CLSA (Closed Loop Stripping Apparatus)

In contrast to previous investigations the closed loop stripping apparatus is used to determine the components of the volatile leaf oil ofPicea sp. The samples, obtained by this extraction, were separated on glass capillary columns and identified by GC/MS. Finally, the advantages of this method, compared with the conventional steam-distillation, and the composition of some problematic constituents are discussed.