Christina Plank

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.

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.

Coupled column chromatography in chiral separations: systems employing β-eyclodextrin phases for chiral separation

Abstract Two-dimensional chromatographic systems were evaluated which combine a β-cyclodextrin (β-CD)-containing column for the optical resolution of enantiomers with a non-chiral column for the preseparation of these enantiomers from other solutes or impurities. β-CD is used either as a chemically bonded stationary phase or as a mobile phase additive. This multi-column system allows the accurate determination of the enantiomeric composition even in complex samples and improves the significance and reliability of the results. The system was evaluated with respect to peak dilation caused by the carry-over, the maximum carry-over volume up to which severe adverse effects on the resolution can be avoided, and the implications with regard to sensitivity.

Lower flange modification improves performance of the Macintosh, but not the Miller laryngoscope blade

PurposeIn order to minimize the potential for dental damage and to improve laryngeal visualization during tracheal intubation, two commonly used laryngoscope blades were modified and compared in a clinical setting: the Miller laryngoscope blade and the Macintosh laryngoscope blade. Modified versions of both laryngoscope blades with a lowered heel (Callander modification) at the proximal end of the blade were compared to standard blades.MethodsForty patients scheduled for general anesthesia requiring endotracheal intubation were studied prospectively. Preoperatively, the patients’ airways were evaluated according to Mallampati score, thyromental distance and interincisor gap. After induction of anesthesia laryngoscopy was performed with the original laryngoscope and its modified counterpart in random order. A lateral x-ray of the neck was taken after the optimal view had been obtained, and blade-tooth distance, laryngeal view, blade-tooth contact and need for assistance were measured. Using angular calculations the laryngoscopes were analyzed at different insertion depths on graph paper, and the results were compared with data from the lateral x-rays.ResultsWith a modified Macintosh blade the blade-tooth distance was significantly greater in comparison to the original design (2.5 ± 2.1 cmvs 0.2 ± 0.1 cm,P < 0.01). Consequently the number of blade-tooth contacts was significantly lower (20%vs 75%,P < 0.05). The best laryngeal view could be obtained using a modified Macintosh laryngoscope. With a modified Miller laryngoscope laryngeal visibility was not improved and assistance was required more often to achieve adequate intubating conditions (35%vs 5%,P < 0.05).ConclusionA reduction of the proximal flange of a Miller blade decreases the blade’s effectiveness for laryngeal visualization, whereas a similar modification of a Macintosh blade increases blade-tooth distance, decreases the number of blade tooth contacts and provides a better laryngeal view.RésuméObjectifPour réduire le risque de dommage aux dents et pour améliorer la visualisation du larynx pendant ľintubation endotrachéale, deux lames de laryngoscope fréquemment utilisées ont été modifiées et comparées en situation clinique, celles des laryngoscopes Miller et Macintosh. Les versions modifiées des deux lames, munies ďun talon plus bas à ľextrémité proximale (modification Callander), ont été comparées aux lames régulières.MéthodeQuarante patients devant subir une anesthésie générale avec intubation endotrachéale ont fait ľobjet ďune étude prospective. Ľévaluation préopératoire des voies respiratoires selon le score de Mallampati a révélé la distance thyromentonnière et ľespace interincisive. Après ľinduction de ľanesthésie, la laryngoscopie a été réalisée avec le laryngoscope original et sa version modifiée suivant un ordre aléatoire. Une fois la vision optimale obtenue, une radiographie latérale du cou a été prise, puis la distance entre la lame et les dents, la vision laryngée, la présence de contact entre la lame et les dents et la nécessité ďune assistance ont été évaluées. D’après le calcul des angles, une analyse graphique des laryngoscopes a été faite pour différentes profondeurs ďinsertion et les résultats comparés avec les données de la radiographie latérale.RésultatsAvec la lame Macintosh modifiée, la distance dentlame a été significativement plus grande qu’avec la lame originale (2,5 ± 2,1 cm vs 0,2 ± 0,1 cm, P < 0,01). Le nombre de contacts dent-lame a donc été significativement plus bas (20 % vs 75 %, P < 0,05). La meilleure vision laryngée a pu être obtenue avec une lame Macintosh modifiée. Avec le laryngoscope Miller modifié, la visibilité du larynx n’était pas améliorée et une assistance a été plus souvent requise pour atteindre des conditions ďintubation adéquates (35 % vs 5 %, P < 0,05).ConclusionUne réduction du manche proximal de la lame Miller diminue la qualité de la visualisation laryngée obtenue tandis qu’une modification similaire de la lame Macintosh améliore la distance dent-lame, diminue le nombre de contacts dent-lame et fournit une meilleure vision du larynx.

At a Distance from the Territory: Distal Drivers in the (Re)territorialization of Oil Palm Plantations in Indonesia

Exponential growth in oil palm land and palm oil production in Indonesia currently makes the country the world’s largest producer of this vegetable oil. Throughout its tumultuous political past from the 1960s until today, conditions were created which enabled the expansion of oil palm plantations. Under President Suharto’s “New Order,” territorialization processes were used to bring land and people under the control of an increasingly powerful central government. Plantations were instrumental in this regard and additionally formed the basis for the production of palm oil as an important export commodity in the opening of the Indonesian economy. In the wake of the 1997/1998 Asian economic crisis and with the end of Suharto’s rule, Indonesia entered a period of reform marked by decentralization and reterritorialization processes. Oil palm plantations continued to grow as foreign investment and plantation ownership by private businesses became increasingly relevant. Throughout both of these periods, the land-use decisions, which fostered the expansion of oil palm plantations, were not made by the people on the ground, but at a spatial, temporal, and functional “distance.” While distal drivers strongly shaped the development of land use, the consequences of these changes had little impact on the drivers. As plantations expanded farther into territories already claimed for other forms of land use (e.g., rainforest, subsistence agriculture land, indigenous land), they were increasingly likely to confront competing claims to land. Under the perceived greater political freedom of the reform period, the competing claims more often triggered conflicts, which, however, had limited bearing on these distal drivers.