On-line coupling of sequential injection extraction with restricted-access materials for sample clean-up and analysis of drugs in biological matrix

In this contribution, the on-line coupling of solid phase extraction (SPE), based on a restricted-access material (RAM), with sequential injection technique (SIA) for the analysis of biological samples, is described. The SIA-RAM system was tested with a new potential antileucotrienic drug (VUFB-19363 (Quinlukast)) for serum analysis. The method is based on SPE with the novel internal-surface reversed-phase column packing material-alkyl-diol silica (ADS). The supports tolerate direct and repetitive injection of proteinaceous fluids (plasma, serum) and allow reversed-phase partitioning at the internal surface. A column packed with a 25 microm C18 alkyl-diol support was used for direct serum injection. Using a 6-port selection valve and the system of three mobile phases, the polar matrix compounds and metabolites are removed by sequentially aspirated mobile phases with lower content of the organic part (methanol-water (2:98) and following acetonitrile-water (20:80)) to the waste, and then, the analyte enriched on the column is eluted by a strong mobile phase (acetonitrile-methanol-water (40:20:40)) to the UV detector without transfer loss. With the fully automated SIA system, a total analysis time of less than 10 min was achieved. The only off-line sample pre-treatment step required to remove particulate matter was centrifugation. The studies showed a range of linearity (2-40 microg ml(-1)) and a high recovery (93.6-96.8%) of drug from the biological matrix with coefficients of variation (RSD) less than 5.0% (n = 6). This paper introduces a new, simple and robust analytical technique suitable for screening determination and direct analysis of drugs in biological materials.     

Polymers having stable radicals. II. Synthesis of nitroxyl polymers from 4-methacryloyl derivatives of 1-hydroxy-2,2,6,6-tetramethylpiperidine

Polymers having stable pendant . radicals were synthesized through their precursor polymers by oxidizing them in air or by H₂O₂–Na₂WO₄. Hydrochlorides and sulfates of 4-methacryloylamino- and 4-methacryloyloxy-1-hydroxy-2,2,6,6-tetramethylpiperidines were synthesized as precursor monomers and polymerized by using α,α′-azobisisobutyronitrile under appropriate conditions to precursor polymers of high molecular weight: poly-4-methacryloylamino-/oxy-1-hydroxy-2,2,6,6-tetramethylpiperidinehydrochlorides and sulfates. The precursor polymers were converted to polymers having nitroxyl stable radicals, i.e., poly-4-methacryloylamino-/oxy-2,2,6,6-tetramethylpiperidine-1-oxyls, by oxidation in air or with H₂O₂–Na₂WO₄ without any main-chain scission. The structure of the resultant stable radical polymers was determined by infrared, ultraviolet, and ESR spectroscopy. Based on the results of spectroscopic analysis and Kjeldahl analysis, the transformation from precursors to nitroxyl stable radical polymers was found to be quantitative. Investigations on the applicability of polymeric nitroxyl radicals to oxidation-reduction reactions were attempted by means of polarography; the reduction half-wave potential was found to be ?1.16 V for the mercury pool.     

Grafting of a bicycloorthoester onto polymers bearing sulfonium salt structures

Graft copolymerization of a bicycloorthoester (BOE) with polymer-supported sulfonium salts was studied. Several polymer-supported sulfonium salts were prepared by the homopolymerizations of p-vinylbenzyl tetramethylenesulfonium hexafluoroantimonate ( 2 ) and 4-(p-vinylphenyl)butyl tetramethylenesulfonium hexafluoroantimonate ( 3 ), and by the copolymerizations of 2 with some vinyl monomers (n-butyl vinyl ether, styrene, acrylonitrile, and p-styrenesulfonic acid potassium salt). These sulfonium salts could initiate the polymerization of BOE to give grafted polymers. Temperature dependences of the catalytic activity of them were not so dramatic as that of benzyl tetramethylenesulfonium hexafluoroantimonate ( 1 ), but the activities of them were higher than that of 1 at temperatures lower than 80°C. The conversion of BOE in the polymerizations with these polymer initiators was ca. 30–70% at 120°C for 7 h. An effect of the comonomer structure on the catalytic activity was observed and styrene was the best comonomer for 2 in terms of the reactivity of the copolymer. The spacer-modified sulfonium salt (homopolymer of 3 ) was slightly lower than polymer-supported benzyl type sulfonium salt (homopolymer of 2 ) in the catalytic activity.     

Revised analysis of the structure of the v1 band of methane

The CARS spectrum of the v₁ band of ₁₂CH₄ at a pressure of 14 mbar was recorded using cw excitation in the cavity of a ring argon ion laser. The analysis of the intensity profile of the obarred spectrum led to the detection of inconsistencies with the hitherto proposed calculated positions of transitions with J = 7 to J = 10 and to a relocation of the corresponding lines.     

New tridentate cyclometalated platinum(II) and palladium(II) complexes of N,2-diphenyl-8-quinolinamine: syntheses, crystal structures, and photophysical properties

A new tridentate cyclometalated platinum(II) complex derived from N,2-diphenyl-8-quinolinamine, which consists of two crystallographic independent molecules with two intermolecular N-H-Cl-Pt hydrogen bonds forming a dimer, exhibited a low-energy luminescence at ca. 740 nm in a 1 × 10⁻³ M dichloromethane solution and a strong emission centered at 670 nm in a solid state, but the analogous palladium(II) complex was nonemissive at room temperature.     

Hyperfine interactions in icosahedral quasicrystals: a Mössbauer study

Icosahedral Al₆₅Cu₂₀Fe₁₅ and Al₄₀Cu_9.9Ge₂₅Mn₂₅ ⁵⁷Fe_0.1 quasicrystals are studied using⁵⁷Fe transmission Mössbauer experiments. The spectra are analyzed by distributions of electric-quadrupole interaction accounting for line asymmetries. Temperature dependences of the hyperfine parameters derived comprising average values ofP() distributions, corresponding standard deviations and center shifts are presented in a whole range from 8 to 300 K.     

Local order of icosahedral quasicrystals studied by Mössbauer spectroscopy

Thermodynamically stable Al-Cu-Fe and Fe-doped ferromagnetic Al-Cu-Ge-Mn icosahedral quasicrystals are studied by⁵⁷Fe transmission Mössbauer spectroscopy and X-ray diffraction experiments. Al₆₅Cu₂₀Fe₁₅ quasicrystalline alloy was subjected to a mechanical grinding (MG) for up to 800 hours in a ball mill. Presence of the amorphous phase which co-exists with the quasicrystalline one is revealed in the early stage of MG. Mössbauer measurements were performed on icosahedral Al₄₀Cu_10–x Ge₂₅Mn₂₅Fe _x quasicrystal (x0.1; 3) in a temperature range from 10 K to 548 K. It was found that a magnetic transition occurs at about 30 K which is far belowT _c reported in the literature. It is concluded that AlGeMn ferromagnet which is present in the samples does not affect the magnetic transition observed and the transition is an intrinsic property of the Al-Cu-Ge-Mn host alloy.Samples of icosahedral quasicrystals were kindly provided by Profs. A. Inoue, T. Masumoto and P. H. Shingu. Ball milling was performed in Kyoto University by a courtesy of Prof. P. H. Shingu. This work was supported by the project for priority areas on properties of quasicrystals (No. 01630003) from the Japanese Ministry of Education, Science and Culture.     

Syntheses of polyurethanes derived from oximes and their photodegradation

Polyoxime-urethanes have been synthesized from dioximes and diisocyanates, and their structures have been ascertained by elemental analysis and infrared spectroscopy. They can be represented by the general formula: These polymer films were photolyzed by using a high-pressure 100-W mercury lamp, and the rate of decomposition of the N? O bond was determined by use of ultraviolet and infrared spectra, or comparing the photochemical behavior with that of corresponding model compounds. Upon irradiating these polymers in the presence or absence of sensitizers or a hydrogen donor, there were obtained photolyzed polymers of low molecular weight, of which the molecular weights were estimated by observing the viscosity changes. To deduce the mechanism of photodegradation of polyoxime-urethane, photolysis of benzophenone oxime-phenyl urethane was investigated as a model compound.     

Involvement of human small fragment nuclease in the resistance of human cells to UV-C-induced cell death

Human small fragment nuclease (Sfn) is one of the cellular proteins that were reported to degrade small, single-stranded DNA and RNA. However, the biological role of Sfn in cellular response to various stressors such as UV-C (mainly 254 nm wavelength ultraviolet ray) remains unclear. We have examined whether modulation of human SFN gene expression affects cell survival capacity against UV-C-induced cell death, analyzing colony survival ability in UV-C-sensitive human RSa cells treated with short double-stranded RNA (siRNA) specific for SFN messenger RNA (mRNA). The expression levels of SFN mRNA in the siRNA-treated RSa cells decreased to about 15% compared with those in the control siRNA-treated cells. The siRNA-treated RSa cells showed lower colony survival and higher activity of caspase-3 after UV-C irradiation than the control siRNA-treated RSa cells. Furthermore, the removal capacity of cyclobutane pyrimidine dimers (CPD) in the siRNA-treated RSa cells decreased compared with the control siRNA-treated RSa cells. There was no difference in the colony survival and CPD removal capacity after UV-C irradiation between the control siRNA-treated RSa cells and mock-treated RSa cells. These results suggest that SFN expression is involved in resistance of RSa cells to UV-C-induced cell death through the roles it plays in the DNA repair process.