Gas chromatography of amino acids: Use of a fused-silica capillary column in the determination of plasma amino acids

A capillary chromatographic procedure using a fused silica column is described which can be used to quantitatively determine amino acids in plasma following the pre-chromatographic “clean-up” described in a recent paper [1]. In substituting this procedure for that involving a packed column, advantage has been taken of the greater resolving power to separate amino acids from background component peaks. In order to extend this advantage and provide a sound basis for quantitative analysis, the technique of cold on-column injection was employed. As a result, good precision of standard analysis was obtained with relative standard deviation (RSD) values for all amino acids of less than 4%. Application of the entire procedure to plasma samples yields RSD values of better than 10% for all amino acids with recoveries ranging from 72% to 104%. Simultaneous determination of plasma amino acid levels by gas chromatography (GC) using capillary columns and by classical ion exchange (CIE) showed reasonable agreement. Statistical evaluation showed no significant difference between twelve amino acids. Values for the remaining two, namely, phenylalanine and histidine are significantly different (p < 0.005). Comparison of the values obtained from GC capillary and packed columns reveals no significant difference between fourteen amino acids. Significant differences exist between results for phenylalanine and tyrosine (p < 0.001). It is concluded that there is good agreement between data obtained by GC capillary and CIE techniques and that differences between results for phenylalanine and histidine are method related.     

Carbonyl-carboxylato-ruthenium complexes incorporating diimine ligands and unexpected cyclometalation of carboxylate ligands

We report two new synthetic routes to the dinuclear Ru(I) complexes, [Ru(I)(2)(RCO(2))(CO)(4)(N( wedge )N)(2)](+) (N( wedge )N = 2,2'-bipyridine or 1,10-phenanthroline derivatives) that use RuCl(3).3H(2)O as a starting material. Direct addition of the bidentate diimine ligand to a methanolic solution of [Ru(CO)(2)Cl(2)](n) and sodium acetate yielded a mixture of [Ru(I)(2)(MeCO(2))(CO)(4)(N( wedge )N)(2)](+) (N( wedge )N = 4,4'-dmbpy, and 5,6-dmphen), and [Ru(II)(MeCO(2))(2)(CO)(2)(N( wedge )N)] (N( wedge )N = 4,4'-dmbpy and 5,5'-dmbpy). Single-crystal X-ray studies confirmed that the Ru(II) complexes had a trans-acetate-cis-carbonyl arrangement of the ligands. In contrast, the use of sodium benzoate resulted in the unexpected formation of a Ru-C bond producing ortho-cyclometalated complexes, [Ru(II)(O(2)CC(6)H(4))(CO)(2)(N( wedge )N)], where N( wedge )N = bpy or phen. A second approach used ligand exchange between a bidentate ligand (N( wedge )N) and the pyridine ligands of [Ru(I)(RCO(2))(CO)(2)(py)](2) to convert these neutral complexes into [Ru(I)(2)(RCO(2))(CO)(4)(N( wedge )N)(2)](+). This method, although it involved more steps, was applicable for a wider variety of diimine ligands (R = Me and N( wedge )N = 4,4'-dmbpy, 5,5'-dmbpy, 5,6-dmphen; R = Ph and N( wedge )N = bpy, phen, 5,6-dmphen).     

Synthesis,Mössbauer,and IP spectroscopic studies and thermal behavior of diorganotin(IV) complexes with carbohydrate ligands

A series of diethyltin(IV) complexes with carbohydrate ligands (aldoses, polyalcohols, sugar acids, sugar amines, and di- and trisaccharides] was prepared. The compositions of the complexes were determined by standard analytical methods. The results showed that complexes formed containing the diethyltin moiety and the carbohydrate ligand in 11 ratio. The IR spectra were consistent with the presence of tin—carbohydrate oxygen vibrations in the compounds. The comparison of experimental quadrupole splitting values with those calculated on the basis of the partial quadrupole splitting (PQS) concept revealed the compounds to be of three types: complexes in with the central tin(IV) atoms are present in purely trigonal bipyramidal surroundings, ones with the tin(IV) atoms present in purely octahedral surroundings, or ones with both octahedral and trigonal bipyramidal arrangements in approximately 11 ratio. The thermal decompositions showed that some of the complexes decompose via the reduction of tin(IV) to SnO as the final tin-containing product, some of them decompose without reduction, to give SnO₂, and some decompose to give indefinite final tin-containing products.     

Stochastic and Deterministic Simulation of Nonisothermal Crystallization of Polymers

This paper is devoted to the numerical simulation of nonisothermal crystallization of polymers, which may be modelled as a stochastic birth-and-growth process. One of the main aims is to develop efficient algorithms for the stochastic simulation of such process. We put a special emphasis on the problem of computing the surface density of crystals, which is an important factor for the mechanical properties of the solidified material. Moreover, an averaged deterministic model, designed as an approximation in the case of many small crystals (which is very frequent in industrial applications), is presented, and the results of numerical simulations are compared with the corresponding simulations of the stochastic model.     

First synthesis of totally orthogonal protected alpha-(trifluoromethyl)- and alpha-(difluoromethyl)arginines.

The first synthesis of a series of totally orthogonal protected racemic alpha-(trifluoromethyl)- and alpha-(difluoromethyl)arginines is described. The key steps of the synthesis are the mild guanidinylation procedure and the selective hydrogenation of a CC triple bond in the presence of a Cbz-group.     

Plasma Induced Addition of Active Functional Groups to Biochar for Elemental Mercury Removal

Plasma Chemistry and Plasma Processing - The mercury removal capacity of biochar can be improved by plasma modification and the functional group is an important factor affecting the mercury...