Reversible Sorptive Preconcentration of Noble Metals Followed by FI-ICP-MS Determination.

In this paper, we propose the combined procedure of noble metal (NM) determination, including fire assay, acid digestion, and reversible dynamic sorptive preconcentration, followed by flow-injection ICP-MS. Reversible preconcentration of all NMs was carried out using micro-column packed new PVBC-VP sorbent and elution with a mixture of thiourea, potassium thiocyanate, and HCl, which recovers Pd, Ir, Pt, and Au by 95% and Ru, and Rh by 90%. The proposed procedure was approved using certified reference materials.

50 years of chiral liquid Chromatography. How it started.

The birth of modern chiral liquid chromatography can be traced back to the years 1968-71 when the first complete resolution of a racemic amino acid was obtained and presented in the literature. Extreme enantioselectivity was achieved due to the introduction of ligand exchange principle, i.e.

Trace enrichment of phenylcarboxylic acids from a model biological fluid and serum of human blood.

The study was focused on the development of a solid-phase extraction protocol for seven phenylcarboxylic acids from albumin solutions by using unmodified hyper-cross-linked polystyrene restricted access materials with crosslinking degrees varying from 100 to 400% (four of the acids are known to be markers of sepsis). The breakthrough volume of the most hydrophilic 3,4-dihydroxybenzoic acid rises as the sorbent bridging extent grows. Inversely, the breakthrough volume of the most hydrophobic 3-phenylpropionic acid was found to decrease considerably when the degree of crosslinking exceeds 200%.

Hypercrosslinked polymeric restricted access materials for analysis of biological fluids.

New restricted access materials based on microporous hypercrosslinked polystyrene have been developed. The materials are aimed to use as packings for solid-phase extraction cartridges to isolate low-molecular-weight analytes from biological fluids (for instance, blood plasma or serum). Two features distinguish these polymers from all known restricted access materials.

Enantiomeric-Enriched Ferrocenes: Synthesis, Chiral Resolution, and Mathematic Evaluation of CD-chiral Selector Energies with Ferrocene-Conjugates.

Enantiomeric-enriched ferrocene-modified pyrazoles were synthesized via the reaction of the ferrocene alcohol, ()-FcCH(OH)CH₃ (Fc = ferrocenyl), with various pyrazoles in acidic conditions at room temperature within several minutes. X-ray structural data for racemic (,)-1-(3,5-dimethyl pyrazolyl)ethyl ferrocene () and its ()-enantiomer ()- were determined. A series of racemic pyrazolylalkyl ferrocenes was separated into enantiomers by analytical HPLC on β- and γ-cyclodextrins (CD) chiral stationary phases.

Physicochemical and adsorption properties of hypercross-linked polystyrene with ultimate cross-linking density.

The paper describes unexpected properties of hypercross-linked polystyrenes with ultimate cross-linking degrees of 300, 400, and 500%, where three, four, or five methylene links, respectively, could bind each polystyrene phenyl ring to its spacious neighbors. The polymers exhibit a strong electron spin resonance signal, unusual spectra in IR, UV, and visible ranges, and they are not typical dielectrics. The nonfunctionalized hypercross-linked polymers absorb significant amounts of inorganic acids, salts, and bases due to interactions of protons or other cations with electron-donating fragments of the aromatic network with the high extent of mutual connectivity and also due to dispersion interactions of anions with the polymer matrix.

The use of phosphite-type ligands in the Ir-catalyzed asymmetric hydrogenation of heterocyclic compounds.

A series of chiral phosphite-type ligands was tested in asymmetric Ir-catalyzed hydrogenation of quinolines and 2,4,5,6-tetrahydro-1H-pyrazino(3,2,1-j,k)carbazole. Hydrogenation of quinaldine hydrochloride provided superior enantioselectivity up to 65% ee compared to quinaldine free base. The ligands were tested for the first time in the asymmetric Ir-Ircatalyzed hydrogenation of 2,4,5,6-tetrahydro-1H-pyrazino(3,2,1-j,k)carbazole yielding the antidepressant drug, pirlindole.

Paradoxes of thermodynamics of swelling equilibria of polymers in liquids and vapors.

An automatic registration of the changing size of a single spherical microbead of a cross-linked polymer was applied for studying the swelling process of the bead by the sorption of vapors and/or liquids. Many representatives of all three basic types of polymeric networks, gel-type, hypercrosslinked, and macroporous, were examined. Only the first two display large volume changes and prove suitable for following the kinetics and extent of swelling by the above dilatometric technique.

Application of a new amidophosphite ligand to Rh-catalyzed asymmetric hydrogenation of β-dehydroamino acid derivatives in supercritical carbon dioxide: activation effect of protic Co-solvents.

New chiral amidophosphite ligand was synthesized and tested in the Rh-catalyzed asymmetric hydrogenation of (Z)-β-(acylamino)acrylates in protic solvents and supercritical carbon dioxide (scCO(2) ) The catalytic performance is affected greatly by the acidity of the solvents. Better enantioselectivity (up to 88% ee) was achieved in scCO(2) containing 1,1,1,3,3,3-hexafluoro-2-propanol, compared to neat protic solvents.

Carborane complexes of ruthenium(III): studies on thermal reaction chemistry and the catalyst design for atom transfer radical polymerization of methyl methacrylate.

The heating of the 18-electron complex [3,3-(dppb)-3-H-3-Cl-closo-3,1,2-RuC(2)B(9)H(11)] (3) in benzene at 80 °C in the presence of a small amount of CCl(4) as initiator afforded paramagnetic 17-electron species [3,3-(dppb)-3-Cl-closo-3,1,2-RuC(2)B(9)H(11)] (4) along with minor amounts of two P-phenylene ortho-cycloboronated derivatives [3-Cl-3,3,8-{Ph(2)P(CH(2))(4)PPh-μ-(C(6)H(4)-ortho)}-closo-3,1,2-RuC(2)B(9)H(10)] (5) and [3,7-Cl(2)-3,3,8-{Ph(2)P(CH(2))(4)PPh-μ-(C(6)H(4)-ortho)}-closo-3,1,2-RuC(2)B(9)H(10)] (6) in total yield of ca. 80%. The heating of either 3 or 4 in toluene at 95 °C in the absence of CCl(4) led to the selective formation of 5, which was isolated in 64% and 46% yield, respectively.

Chiral phosphites derived from carboranes: electronic effect in catalytic asymmetric hydrogenation.

A series of new fine-tunable monodentate phosphite and phosphoramidite ligands based on carboranes have been synthesized and used for asymmetric Rh-catalyzed hydrogenation of prochiral olefins with the result of up to 99.8% ee. Dependence of the enantioselectivity on the electron-withdrawing or electron-donating properties of the carboranyl substituent has been studied.

Novel P,N-bidentate phosphite ligands in asymmetric catalysis.

Results achieved by the authors in the synthesis of chiral P,N-phosphite ligands are summarized. Three groups of new chiral P,N-phosphites are discussed, namely, ligands derived from 1,1'-bi-2-naphthol, ligands possessing an acyclic phosphorus center, and P*-chiral ligands derived from (S)-2-anilinomethylpyrrolidine. An overview of complexation of the ligands with Rh(I) and Pd(II) precursors is given.

Enantioselective ligand exchange in modern separation techniques.

As a follow-up to a series of review articles on enantioselective ligand exchange chromatography, the present contribution critically evaluates achievements in this area of active and successful research which have been reported in the scientific since 1992. Also discussed is enantioselective ligand exchange in electromigration techniques which have developed especially fruitfully during the last decade.