Characterization of cocoa butters and other vegetable fats by pyrolysis-mass spectrometry

Pyrolysis Mass Spectrometry (Py-MS) was used for the discrimination of cocoa butters from other vegetable fats. Mass spectra ranging from 50 amu to 250 amu were analyzed by principal component analysis (PCA) and with neural nets. The application of neural nets leads to a good discrimination between the two classes. Detailed analysis of the nets revealed that only the first 60 masses were used within the net. The use of PCA requires a careful selection of the number of masses included in the calculation. Canonical variance analysis was applied to determine the significant masses. Optimal performance of PCA was observed only using the first 22 significant masses. Most of these masses were different from the ones used by the neural net. It seems that the mass spectra obtained by Py-MS contain sufficient information for the discrimination of pure cocoa butter from other vegetable fats, but none of the methods seems to be able to extract all information available. Neural net provides a very robust method for this task and no prior data selection was necessary. Received: 13 May 1996 / Revised: 7 August 1996 / Accepted: 7 August 1996     

Screening for the beta-39 mutation in thalassemia by capillary electrophoresis in free solution in strongly acidic, isoelectric buffers

A novel method is reported for screening for point mutations in genomic DNA: free-zone capillary electrophoresis in very acidic buffers. This method exploits the charge difference among the four different bases (C, T, A, G) in a pH window between 2.5 and 3.5, where the four titration curves fan out. The method is applied to the detection of the beta-39 missense mutation in the beta-globin gene in thalassemias. A 60-mer fragment straddling the mutation site has been amplified. In an isoelectric buffer (iminodiacetic acid) of pH 3.3, partial resolution between the wild type and mutated strands is obtained. In a pH 3.0 phosphate buffer, baseline resolution is achieved between the two strands in a heterozygous individual. Due to the short size of the amplified fragment, this method can only be applied to routine screening for known mutations because resolution was lost in a fragment 100 bases long.     

Labelling of organotin compounds for fluorimetric detection

A systematic study of the fluorescence of complexes of some flavone derivatives with organotin compounds in hexane and in an aqueous micellar medium on Triton X-100 is reported. Some relationships between fluorescence intensity and the structure of the fluorogenic reagent or that of the organotin compound can be deduced, and the most suitable reagent for each organotin species can be chosen on the basis of sensitivity and selectivity. Results point out that flavone derivatives are appropriate post-column derivatization reagents for organotin compounds in liquid chromatography.     

Integrated production of ethanol fuel and protein from Coastal Bermudagrass

The herbaceous crops that may provide fermentable carbohydrates for production of fuels and chemicals also contain 10–20% protein. Protein coproduction with biomass-derived fuels and chemicals has important advantages: (1) food and fuel production can be integrated, and (2) protein is a high-value product that may significantly improve overall process economics. We report the results of an integrated approach to producing protein and fermentable sugars from one herbaceous species, Coastal Bermudagrass (CBG). The ammonia fiber explosion (AFEX) process makes possible over 90% conversion of cellulose and hemicellulose to simple sugars (about 650 mg reducing sugars/g dry CBG) at 5 IU cellulase/g vs < 20% conversion for untreated CBG. The AFEX treatment also improves protein extraction from CBG; over 80% protein recovery is possible from AFEX-treated CBG vs about 30% recovery from untreated CBG.     

Antioxidant activity of aryltetralone lignans and derivatives from Virola sebifera (Aubl.)

Aryltetralone lignans bearing methylenedioxy groups (1a-b; 2a-b) were isolated from seeds of Virola sebifera. Their antioxidant activities were evaluated by inhibition of lipid peroxidation as indicated by TBARS and chemiluminescence emission (CL) assays. The lignan 1c, 'having a 2'-hydroxy-4',5'-methylenedioxyphenyl group, was the most active compound with TBARS/CL Q 1/2 values of 0.89 and 0.10 microg/mL, respectively. The catechol derivatives 3 and 4, obtained by demethylenation of lignans 1a and 2a, were of similar activity to 1c, and all were much more effective as antioxidants than alpha-tocopherol.     

Copper corrosion in buffered and non-buffered synthetic seawater: a comparative study

The electrochemical behaviour of copper in neutral buffered and non-buffered synthetic seawater and in pure chloride solutions has been studied by cyclic voltammetry, weight loss measurements, open circuit potential and scanning electron microscopy (SEM). Values of the repassivation potentials of Cu in non-buffered and buffered synthetic seawater, at 50 mV s^–1, were 0.12 and 0.46 V vs. SCE, respectively. The sharpness, heights and location of the different peaks as well as their charges were shown to be influenced by the composition of the solution, buffering conditions, deoxygenation, polarization potential and time. High chloride concentrations lead to higher oxidation charges. The anodic and the cathodic charges were shown to increase as the chloride concentration increases. The open circuit potential transients of copper in non-deoxygenated, non-buffered synthetic seawater indicate pitting from the beginning of the exposure, while in buffered solutions the pitting appeared only after a quite long exposure period, i.e. after 40 days. Corrosion rates of Cu samples after 3 months of immersion were higher in solutions of pure chloride (0.5 M) than in synthetic seawater. After six months the differences were even more noticeable. SEM images have showed a somewhat higher density of pits on copper samples immersed in the chloride solution (0.5 M), in comparison with those in synthetic seawater.     

A study of substituent effect on 1H and 13C nmr spectra of N‐ and C‐substituted carbazoles

¹H and ¹³C nmr spectra of several N‐ and C‐substituted carbazoles (Series 1, 2, 3 and 4) were measured. Correlations between chemical shifts and substituent constants show that these parameters describe properly the substituent effect on the nmr phenomena. Atomic charge densities for carbazoles of Series 1, 2, 3 and 4 were calculated by using the semi empirical PM3 method. These values also show a linear correlation with the ¹³C chemical shifts. The synthesis of several carbazole derivatives 1a – 1g, 2a – 2g, 3a – 3j and 4a – 4g have been carried out according to literature procedures. The carbazoles 3i, 3j and 4c have been synthesized and fully characterized for the first time.     

Die Bildungswärmen von MnSi1,73, MnSi,Mn5Si3 und Mn3Si

By means of vapor pressure measurements using theTorker method (Torsion-Knudsen Effusion Recoil) as well as theKnudsen tanspiration technique in connection with a mass spectrometer, the heats of formation of the following compounds were found to be –6.5±0.7 kcal/g atom (Mn_0.366Si_0.634), –7.8±0.6 kcal/g atom (Mn_0.50Si_0.50), –7.3±0.6 kcal/g atom (Mn_0.625Si_0.375), and –6.6±0.6 kcal/g atom (Mn_0.75Si_0.25).

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Simple, rapid and selective method using high-performance liquid chromatography for the determination of bretylium in plasma.

A high-performance liquid chromatographic method with ultraviolet detection has been developed for the determination of bretylium in plasma. Following a single-step solid-phase extraction procedure, bretylium is selectively isolated and well recovered from plasma. The assay sensitivity is 0.156 micrograms/ml from 250-microliters plasma samples and its linearity was assessed up to 40 micrograms/ml. The method is accurate (101.0 +/- 5.4%) and precise (maximum coefficient of variation of 8%). It provides a simple and time-saving alternative to existing methods and is particularly suitable for pharmacokinetic studies.     

Palladium-catalyzed electrophilic allylation reactions via bis(allyl)palladium complexes and related intermediates

The synthetic scope of the allyl-palladium chemistry can be extended to involve electrophilic reagents. The greatest challenge in these reactions is the catalytic generation of an allyl-palladium intermediate incorporating a nucleophilic allyl moiety. A vast majority of the published reactions that involve palladium-catalyzed allylation of electrophiles proceed via bis(allyl)palladium intermediates. The eta(1)-moiety of the bis(allyl)palladium intermediates reacts with electrophiles, including aldehydes, imines, or Michael acceptors. Recently, catalytic electrophilic allylations via mono-allylpalladium complexes were also presented by employment of so-called "pincer complex" catalysts.