The detection of oxygen in organic compounds with potassium tetrathiocyanato-cobaltate(II)

A new micro or Semimicro test for detection of oxygen in organic compounds is based on the blue colour given on treatment with a solid potassium thiocyanatocobaltate reagent. The test was checked with ca. 500 compounds containing various functional groups; very few anomalous reactions were observed.     

Martin’s axiom and the transitivity ofP c-points

It is shown to be consistent with Martin’s Axiom and >ℵ₁ that every twoP _c-points inβℕ\ℕ have the same topological type. This research was partially supported by NSERC. The author would also like to thank Saharon Shelah for making some enlightening remarks, on an earlier version of this paper, which resulted in Definition 2.3.     

On-line reversed-phase liquid chromatography-capillary gas chromatography using a programmed temperature vaporizer as interface

An on-line reversed-phase LC-GC method involving the use of a Programmed Temperature Vaporizer (PTV) as interface is used for the rapid analysis of sterols. The experimental procedure requires only the use of commercial HPLC and GC equipments and a Rheodyne valve. The LC preseparation can be performed satisfactorily even with aqueous eluents containing up to 25% water. Factorial experimental design is applied to investigate the sensitivity achievable in the analysis with some variables (adsorbent material used in the PTV, particle size and plug length) being considered at two different levels. As a result, the sensitivty can be increased by a factor as large as 35 merely by performing the analysis under the experimental conditions giving the highest response. The use of the proposed configuration allows the transfer of up to 1050 μL from LC into the GC system, 1400 μL/min being the speed of sample introduction. The proposed procedure was succesfully applied to the analysis of real samples.     

Study of the analysis of alkoxyglycerols and other non-polar lipids by liquid chromatography coupled with evaporative light scattering detector

An HPLC method with evaporative light scattering detection (ELSD) for the simultaneous analysis of various lipid classes, particularly alkoxyglycerols and acylglycerols with very similar structure and polarity, has been developed. These lipid classes are frequently found in numerous fats and oils such as shark liver oils and can serve as substrates for lipase-catalyzed reactions. This method utilizes a silica column and a gradient elution of isooctane, methyl tert-butyl ether and 2-propanol in different proportions. Separation between squalene, sterol esters, and fatty acid ethyl esters has been achieved in a time of analysis slightly higher than 8 min. In addition, a good resolution between 1,3-diacylglycerols and free sterols was also attained in the same run, with a broad range of concentrations. Excellent precision regarding the retention times was obtained. The limit of detection for the different lipid classes studied was below 1 microg. Intra-day and inter-day variation of retention times and areas was also evaluated. The relative standard deviation of intra-day variation for retention times and areas never exceeded of 0.1 and 10, respectively. The HPLC-ELSD method was also optimized to separate and quantify the hydrolysis products of alkoxyglycerols and acylglycerols (mono-esterified and non-esterified alkoxyglycerols and mono-esterified and di-esterified acylglycerols) at the same time, rendering a useful method for the study of lipase-catalyzed reactions and a wide variety of fats and oils. The present methodology not only separates 18 different lipid classes with a good reproducibility, but it is also able to estimate the relative proportion in which they are found in a broad range of concentrations.     

A study of human coagulation factor XIII A-subunit by electrospray ionisation mass spectrometry

A study of factor XIII A-subunit has been made by electrospray ionisation mass spectrometry. Factor XIII has been isolated and rigorously purified, and the intact A-subunit protein has been analysed to confirm its molecular weight accurately for the first time. Thrombin proteolysis of the A-subunit has been monitored and the resulting cleavage products, the activated A-subunit protein and the Activation Peptide, have been analysed by electrospray ionisation mass spectrometry to confirm the site of proteolysis. Facile and rapid separation of the Activation Peptide from the activated A-subunit protein has been achieved using simple on-line separation techniques. The molecular weight measurements have been repeated numerous times to provide an indication of the precision and variability of the analyses.     

Synthesis of N′-cyclohexenecarbonyl-substituted hydrazides of 2-aminobenzoic acids and preparation of 3-cyclohexenyl-amido-1,2-dihydroquinazolin-4-ones based on them

N′-Cyclohexenecarbonyl-substituted hydrazides of 2-aminobenzoic acids were obtained from the reaction of isatoic anhydride with monohydrazides of cyclohexenedicarboxylic acid. Reaction of the 2-aminobenzoic acid hydrazides with substituted benzaldehydes gave 3-cyclohexenylamido-1,2-dihydroquinazolin-4-ones. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, 894–898, June, 2007.     

Nonlinear interactions in the density fingering of an acidity front

Density fingering of the chlorite-tetrathionate reaction has been studied experimentally in a Hele-Shaw cell. The initially emerging cellular structure transforms into a single cell with constant--asymmetric and symmetric--shape in narrow reaction vessels. The interactions of fingers in wider Hele-Shaw cells lead to the coarsening of the patterns, however, splitting of fingers is observed as well. The long time evolution has been quantitatively described by the change in the mixing length, i.e., the amplitude of the patterns, and by the power-averaged cell number of the structures.     

Profiling of different bioactive compounds in functional drinks by high-performance liquid chromatography

In the present work, an HPLC method is proposed to simultaneously detect and quantify water- and fat-soluble vitamins, phenolic compounds, carotenoids and chlorophylls in a single run, by using an ultradeactivated C18 column and gradient separation using trifluoroacetic acid, water and methanol. It is shown that the HPLC method provides baseline separation of all these compounds with good resolution values in 40 min. Moreover, other figures of merit of the method show a good linear response and low detection limits for all the compounds considered in the present study. Furthermore, the usefulness of this method is demonstrated via its successful application to the analysis of different beverages from different natural origin (orange, strawberry, apple, peach pineapple, plum and blackcurrant juices, soybean milk, beers) without the need of any previous sample preparation. A good correlation is also found by comparing the total phenol content (measured by Folin-Ciocalteu method) with the sum of total phenolic compounds obtained using the proposed HPLC method. By using statistical tools, the main compounds associated with antioxidant activity of the extracts (measured by 1,1-diphenyl-2-picrylhydrazyl radical scavenging) were assessed.