Aqueous chromatographic system for the quantification of propofol in biological fluids using a temperature-responsive polymer modified stationary phase

A new method for the quantitative analysis of monkey serum propofol, which is widely used as an anaesthetic agent, was developed by utilizing a temperature-responsive polymer of N-isopropylacrylamide (NIPAAm) and butyl methacrylate (BMA) as the stationary phase of HPLC–fluorescence detection. This poly(NIPAAm-co-BMA) copolymer undergoes a reversible phase transition from a hydrophilic to a hydrophobic microstructure when triggered by change in the temperature. Also this chromatographic system is possible to separate the analytes by using only water as a mobile phase. A pretreatment of the serum (80 μL) was only solid-phase extraction, and the recovery rate of propofol and internal standard was more than 77%, respectively. This method covered the calibration range from 0.5 μg/mL to 10 μg/mL and allowed a reproducible quantification of the serum propofol in administrated monkey serum. The intra- and inter-assay relative standard deviations were less than 14.1%. In addition, there was good relationship of the quantification values between the developed method and the widely used reversed-phase HPLC method. Our developed method has proven to be useful for a simple analysis of propofol in clinical practice, because the avoidance of complicated mobile phase preparation was possible, and only temperature changing could regulate the retention time of the analyte. In addition, by using water instead of fossil fuel, it is the ideal analytical method according to green chemistry.     

Non-steady state solidification of the Nd-123 superconducting oxides

Crystal growth of the melt-textured bulk Nd_1+xBa_2−xCu₃O_6+d (Nd123) superconducting oxides was investigated by employing isothermal undercooling solidification with hot-seeding in air. From the relationship between growth length and holding time, the Nd123 crystal was found to have almost stopped growing after a certain growth period, while the growth length increased proportionally to the holding time at an early stage of the crystal growth. As a result of quantitative analysis for the Nd123 crystal of which solidification was terminated, the distribution of the Nd/Ba substitution was observed to decrease in the Nd123 single crystal matrix from the seed crystal to the edge of the Nd123 crystals. Also, the substitution content at the edge of the Nd123 crystal, which corresponds to that at the final stage of the crystal growth, was found to be in good agreement with the minimum substitution of the Nd123 solid solution phase in the equilibrium phase diagram at this process temperature. These compositional changes could be explained using the equilibrium phase diagram as associated with the solid solution formation, which is responsible for the non-steady state solidification of the Nd123 crystals even for the isothermal undercooling processing.     

Critical current density and vortex dynamics in uranium irradiated Co-doped BaFe2As2

We report the effect of defects introduced by heavy-ion irradiation with 2.6 GeV uranium ions at several matching fields in single crystalline Ba(Fe_0.925Co_0.075)₂As₂. The suppression rate of T_c at lower matching fields is larger than that at higher matching fields. The critical current density calculated from magnetic hysteresis loop is enhanced up to 4.1 × 10⁶ A/cm² at 2 K. Clear dips in magnetic hysteresis loops near zero field are observed at high matching fields. Field dependence of normalized relaxation rate is suppressed, and the relationship between the dip and the relaxation rate is discussed.     

Reducing ability of supramolecular C60 dianion toward C=O, C=C and N-N bonds

Different from C60 dianion which readily reacts with electrophiles, supramolecular C60 dianion (2) generated from gamma-cyclodextrin-bicapped C60 (1) and NaBH4 (or diborate) in DMSO-H2O (9:1, v/v) is able to reduce N-N+, C=C-EWG and C=O bonds to provide the respective dihydro derivatives; 1-mediated reduction of acetophenone with NaBH4 in the presence of (Me2N)2CH2 and EtONa gives turn over frequency (TOF)/h of 400.     

Rapid controlled hydrolytic degradation of poly(l-lactic acid) by blending with poly(aspartic acid-co-l-lactide)

Although poly(lactic acid) is known as a biodegradable polymer, its hydrolytic degradation is extremely slow, taking years in water and in the human body. In this study the effects of blending oligomeric poly(aspartic acid-co-lactide) (PALs) on the hydrolytic degradation of poly(l-lactic acid) (PLLA) were studied in detail. It was found that the addition of PAL did not accelerate the hydrolysis of the PLLA in air (25 °C, 60% relative humidity), but significantly accelerated it in a phosphate buffer solution. The degradation rate becomes higher for the blends containing PAL with higher molar ratios of lactide to aspartic acid units, [LA]/[Asp], when PLLA/PAL blends prepared with different PALs are compared at the same PAL concentration. TEM results, in which the distribution of PALs with higher [LA]/[Asp] occurs at a smaller scale in blends, imply that higher miscibility of the PAL with PLLA results in higher contact area between the components, thereby accelerating the degradation efficiently.     

Enantioselective Darzens reaction using organoselenide-lithium hydroxide complexes

Asymmetric Darzens reaction catalyzed by chiral selenides is described. A novel Lewis acid/Brønsted base catalyst formed by C₂ symmetric chiral selenide-bearing isoborneol skeletons, which were readily prepared from (1S)-10-camphorsulfonic acid, and LiOH promoted the reaction of phenacyl bromide with aldehydes to afford the desired trans oxiranes with up to 62% ee.     

Electrochemical genosensors for the detection of Bonamia parasite. Selection of single strand-DNA (ssDNA) probes by simulation of the secondary structure folding

A post-PCR nucleic acid work by comparing experimental data, from electrochemical genosensors, and bioinformatics data, derived from the simulation of the secondary structure folding and prediction of hybridisation reaction, was carried out in order to rationalize the selection of ssDNA probes for the detection of two Bonamia species, B. exitiosa and B. ostreae, parasites of Ostrea edulis.Six ssDNA probes (from 11 to 25 bases in length, 2 thiolated and 4 biotinylated) were selected within different regions of B. ostreae and B. exitiosa PCR amplicons (300 and 304 bases, respectively) with the aim to discriminate between these parasite species. ssDNA amplicons and probes were analyzed separately using the “Mfold Web Server” simulating the secondary structure folding behaviour. The hybridisation of amplicon-probe was predicted by means of “Dinamelt Web Server”. The results were evaluated considering the number of hydrogen bonds broken and formed in the simulated folding and hybridisation process, variance in gaps for each sequence and number of available bases. In the experimental part, thermally denatured PCR products were captured at the sensor interface via sandwich hybridisation with surface-tethered probes (thiolated probes) and biotinylated signalling probes. A convergence between analytical signals and simulated results was observed, indicating the possibility to use bioinformatic data for ssDNA probes selection to be incorporated in genosensors.     

Differential pulse-polarographic determination of organotin compounds coated on fishing nets

Summary The pulse-polarographic behaviour of tributyltin chloride (TBTC) and dibutyltin dichloride (DBTC) in ethanol-water mixtures has been studied. The effects of temperature, pH, modulation amplitude, solvent and supporting electrolyte compositions were investigated. The reduction processes are complicated and pH-dependent. DBTC gave one reversible reduction wave and TBTC showed a quasi-reversible one and also several irreversible waves. Both the organotin compounds in the concentration of 10^–7 mol/l were determined by differential pulse polarography. The method was successfully applied to the analysis of commercially available fishing nets. Detection limits were 2.2×10^–7 and 6.2×10^–8 mol/l for TBTC and DBTC, respectively.

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Differential-puls-polarographische Bestimmung von Organozinnverbindungen auf Fischernetzen

Zusammenfassung Das puls-polarographische Verhalten von Tributylzinnchlorid (TBTC) und Dibutylzinndichlorid (DBTC) in Ethanol-Wasser-Gemischen wurde untersucht und die Wirkung von Temperatur, pH, Modulationsamplitude sowie Zusammensetzung des Lösungsmittels und Leitelektrolyts geprüft. Die Reduktionsprozesse waren kompliziert und abhÄngig vom pH. DBTC ergab eine reversible Reduktionswelle, TBTC eine quasireversible Welle, sowie daneben einige irreversible Wellen. Beide Organozinnverbindungen konnten in einer Konzentration von 10^–7 mol/l durch Differential-Puls-Polarographie bestimmt werden. Die Methode wurde erfolgreich auf die Analyse von handelsüblichen Fischernetzen angewandt. Die Nachweisgrenzen lagen bei 2,2·10^–7 (TBTC) bzw. 6,2 · 10^–8 mol/l (DBTC).

This work was supported in part by a Grant-in-Aid for Scientific Research No. 554164 from the Ministry of Education. The authors wish to thank Mr. Y. Komatsu, Clean Kagaku Co., Tokyo, who offered the fishing net samples.