Organometallic polymers containing tricarbonyl(η4-diene)-ruthenium(0) and -iron(0) as pendant groups

Vinyl ethers containing tricarbonyl(14-η⁴-1,3-pentadiene)-ruthenium(0) and -iron(0) species were prepared utilizing selective dienylation with penta-dienylpotassium and were polymerized with cationic initiators to give high molecular weight polymers. The diene-metal moieties were converted into tricarbonyl(13-η³-allyl)metal species by protonation with dry HCl. Tricarbonyl(3-allyl-14-η⁴-1,3-pentadiene)iron(0) also undergoes cationic polymerization but the presence of its isomer, tricarbonyl(3-propenyl-14-η⁴-1,3-pentadiene)iron(0) inhibits the polymerization.     

Synthesis of cyclotetrapeptides,am-toxin analogs,containing α-hydroxyalanine

Condensation of amide with α-keto acid to yield a α-hydroxyalanine (α-Hyala) or dehydroalanine residue was applied to syntheses of analogs of AM-toxins, cyclotetradepsipeptides. Cyclo(-α-Hyala-L-Ala-L-Val-L-Phe-), cyclo(-α-Hyala-L-Ala-L-Hmb-L-Phe-) and cyclo(-α-Hyala-L-Ala-L-Hmb-L-Tyr-) (Hmb, 2-hydroxy-3-methylbutanoic acid) were obtained from the corresponding pyruvyl-tripeptide amides in good yields by the treatment of anhydrous hydrogen fluoride.     

Enantioselective high-performance liquid chromatography with fluorescence detection of methamphetamine and its metabolites in human urine.

A simple, rapid and highly sensitive high-performance liquid chromatographic method with fluorescence detection for determining the enantiomers of methamphetamine and its major metabolites, amphetamine and p-hydroxymethamphetamine, in urine samples was developed. Using a newly developed reagent for amines, namely, 4-(4,5-diphenyl-1H-imidazol-2-yl)benzoyl chloride, six enantiomers were derivatized under mild conditions (i.e., 10 min at room temperature, pH 9.0) and separated isocratically on a cellulose tris(3,5-dimethylphenylcarbamate) coated silica gel column following a pre-separation on an ODS column within 42 min, and the effluent was monitored at 440 nm (lambda ex 330 nm). Calibration curves for these derivatives using spiked human urine were linear in the range 0.05-100 mumol dm-3 with correlation coefficients > or = 0.999. The detection limits at a signal-to-noise ratio of 3 were 2.8-8.8 fmol per 5 microliters injection. The relative standard deviations of within- (n = 6) and between-day (n = 5) variations were < or = 7.4%. The method was successfully applied to discriminate between (S)-(+)-methamphetamine and its corresponding metabolites found in abusers' urine and their antipodes in a sample taken from a Parkinsonian patient on selegiline (Deprenyl) therapy.     

Behavior of fatty acid during the incubation of bovine serum albumin. Entity of the serum albumin resistant to heat

The solution of bovine serum albumin, incubated at pH 9 (0.1 M Tris-EDTA-boric acid buffer in which 0.15 M KCl was contained) and 65 °C for 60 min, gave zones of undenatured monomer (component 1) and aggregates in the pattern of gel electrophoresis. The component 1, isolated from this solution, contained more fatty acids than the original albumin and than the mixture of aggregates. The aggregates contained substantially no fatty acids. This means that fatty acids are released, when the bovine albumin is denatured accompanying with intra- and intermolecular SH/S-S exchange reactions. Taking palmitic acid as a representative of the long chain fatty acid, a model experiment was performed. The bovine albumin, to which 6 palmitic acids were bound, did not cause the SH/S-S exchange reaction and was not denatured on incubation at pH 9 (0.1 M Tris-EDTA-boric acid buffer) and 65 °C. When the solution of “crystalline bovine albumin” (AF_0.9, A: albumin, F: long chain fatty acid) was incubated at pH 9 (0.1 M Tris-EDTA-boric acid buffer) and 65 °C, 20% of the albumin was not denatured even after prolonged incubation. Further, when the component 1 (AF_3.8), isolated from pre-incubated albumin solution, was incubated again at pH 9 and 65 °C, 58% of the albumin was not denatured even after sufficient time of incubation. Quantitative analysis reveals that the bovine albumin containing 6 fatty acids (AF₆) is not denatured at all, and is the entity of the albumin resistant to heat.     

Measurement of bromate in bread by liquid chromatography with post-column flow reactor detection

This method is suitable for the determination of bromate residues in a variety of baked goods. The peer-verified method trial was performed on white bread, multigrain bread, and coffee cake spiked with known levels of potassium bromate. The analytical portion is extracted with deionized water to remove bromate from the bulk of the baked product. The aqueous extract is carried through a series of steps to remove co-extractives that would interfere with the liquid chromatography (LC) in the determinative step or hasten the deterioration of the LC column. The extract is filtered before passing it through a reversed-phase solid-phase extraction (SPE) column and a cation-exchange column in the silver form to remove lipids and chloride, respectively. Ultrafiltration is then used to remove proteins with molecular weights of >30,000 daltons. Finally, a cation-exchange column in the sodium form is used to remove silver ions from the extract. The determinative step uses LC with a reversed-phase column and an ion-pairing agent in the mobile phase. Detection is based on the post-column reaction of bromate with o-dianisidine to form an oxidation product that is quantitated spectrophotometrically at 450 nm. Overall agreement between the submitting and peer laboratories was quite good. For bromate levels of 10-52 ppb, overall mean recoveries were 76.9 and 78.8% for the submitting and peer laboratories, respectively. The standard deviations were higher for the results of the peer laboratory, probably because of the generally higher level of baseline noise present in the chromatograms. The results demonstrate that the method provides adequate accuracy with low-fat as well as high-fat foods. Bromate at levels as low as 5 ppb (ng/g) can be detected with the method.     

Using Lanthanum Fluoride Fine Particles as Stationary Phase for Thin-Layer Chromatography/Fourier Transform Infrared Spectroscopy Analysis

JPC – Journal of Planar Chromatography – Modern TLC - While in situ TLC/FTIR technique has tremendous potential in the analysis of complex mixtures, the conventional stationary phase,...