Gas chromatography–electron ionization–mass spectrometry quantitation of valproic acid and gabapentin,using dried plasma spots,for therapeutic drug monitoring in in‐home medical care

A simple and sensitive gas chromatography–electron ionization–mass spectrometry (GC‐EI‐MS) method using dried plasma spot testing cards was developed for determination of valproic acid and gabapentin concentrations in human plasma from patients receiving in‐home medical care. We have proposed that a simple, easy and dry sampling method is suitable for in‐home medical patients for therapeutic drug monitoring. Therefore, in the present study, we used recently developed commercially available easy handling cards: Whatman FTA DMPK‐A and Bond Elut DMS. In‐home medical care patients can collect plasma using these simple kits. The spots of plasma on the cards were extracted into methanol and then evaporated to dryness. The residues were trimethylsilylated using N‐methyl‐N‐trimethylsilyltrifluoroacetamide. For GC‐EI‐MS analysis, the calibration curves on both cards were linear from 10 to 200 µg/mL for valproic acid, and from 0.5 to 10 µg/mL for gabapentin. Intra‐ and interday precisions in plasma were both ≤13.0% (coefficient of variation), and the accuracy was between 87.9 and 112% for both cards within the calibration curves. The limits of quantification were 10 µg/mL for valproic acid and 0.5 µg/mL for gabapentin on both cards. We believe that the present method will be useful for in‐home medical care. Copyright © 2014 John Wiley & Sons, Ltd.     

Inner-valence states of N2+ and the dissociation dynamics studied by threshold photoelectron spectroscopy and configuration interaction calculation

The N2(+) states lying in the ionization region of 26-45 eV and the dissociation dynamics are investigated by high-resolution threshold photoelectron spectroscopy and threshold photoelectron-photoion coincidence spectroscopy. The threshold photoelectron spectrum exhibits several broad bands as well as sharp peaks. The band features are assigned to the N2(+) states associated with the removal of an inner-valence electron, by a comparison with a configuration interaction calculation. In contrast, most of the sharp peaks on the threshold photoelectron spectrum are allocated to ionic Rydberg states converging to N2(2+). Dissociation products formed from the inner-valence N2(+) states are determined by threshold photoelectron-photoion coincidence spectroscopy. The dissociation dynamics of the inner-valence ionic states is discussed with reference to the potential energy curves calculated.     

The structures of griseusins A and B,new isochromanquinone antibiotics

The structures of griseusins A and B have been elucidated from chemical and spectroscopic data, and their absolute configurations have also been determined by CD spectroscopy as 4a and 5, respectively. The griseusin is a new type of isochromanquinone antibiotic including a spiro-ring system fused with a juglone moiety. The conversion reaction of griseusin B to griseusin A suggests the biogenetic pathway of the γ-lactone ring formation in some isochromanquinone antibiotics.     

Orthogonal trap time-of-flight mass spectrometer using a collisional damping chamber

We report a new hybrid mass spectrometer, which is a combination of a quadrupole ion trap and an orthogonal time-of-flight (TOF) mass spectrometer. This new configuration consists of a collisional-damping chamber (CDC) inserted between an MSn-capable ion trap and a high-mass-accuracy orthogonal-TOF mass spectrometer. Because the CDC converted an ion packet into an energy-focused and quasi-continuous beam, a high mass resolution of over 10,000 and a high mass accuracy of better than 3 ppm were achieved. Moreover, the ratio of the maximum detectable m/z to the minimum detectable m/z, which is referred to here as the mass window, was improved to more than 10.     

Porphyrin gels reinforced by sol-gel reaction via the organogel phase

Porphyrins bearing four urea-linked dodecyl groups (3a) or four urea-linked triethoxysilylpropyl groups (3TEOS) at their peripheral positions were synthesized. 3a tends to assemble into a sheetlike two-dimensional structure due to the predominant hydrogen-bonding interaction among the urea groups and acts as a moderate gelator of organic solvents. On the other hand, its Cu(II) compelx (3a.Cu) tends to assemble into a fibrous one-dimensional structure due to the predominant porphyrin-porphyrin pi-pi stacking interaction and acts as an excellent gelator of many organic solvents. 3TEOS and 3TEOS.Cu, which also act as gelators, afforded similar superstructures as those of 3a and 3a.Cu, respectively, and as evidenced by SEM and TEM observations and XRD measurements, the original superstructures could be precisely immobilized by in situ sol-gel polycondensation of the triethoxysilyl groups. The TEM images of 3a gels and 3TEOS gels after sol-gel polycondensation showed a fine striped structure, the periodical distance of which was either 2 or 4 nm. X-ray crystallographic analysis of a single crystal obtained from a reference porphyrin bearing four urea-linked butyl groups revealed that there are two different porphyrin-stacked columns in the crystal and both the 2 nm distance and the 4 nm distance can appear, depending on the observation tilting angle. The hybrid gel prepared from 3TEOS.Cu by sol-gel polycondensation showed unique physicochemical properties such as a high sol-gel phase-transition temperature (>160 degrees C), sufficient elasticity, high mechanical strength, etc. Thus, the present study has established new concepts for molecular design of porphyrin-based gelators on the basis of cooperative and/or competitive actions of hydrogen-bonding and pi-pi stacking interactions and for immobilization of their superstructures leading to development of new functional organic/inorganic hybrid materials.     

Accumulated detection of ethidium bromide using a UV-irradiated DNA film modified electrode and its application for electrochemical detection of an environmental pollutant

In this study, DNA was first fabricated on a glassy carbon electrode by UV-irradiation. Through this process, water-soluble DNA was converted into insoluble materials, and a stable DNA film formed on the electrode. Ethidium bromide (EtBr), a typical model substance for harmful chemicals having planer structure, was used as an electroactive intercalator. This allowed our group to investigate the electrochemical and accumulative behaviors of the intercalator in UV-irradiated DNA film on the electrode. The UV-irradiated, DNA film-modified electrode (UV-DNA-FE) made it possible to accumulate electroactive EtBr on the electrode and detect it after accumulation. The modified electrode was used to detect dibenzofuran (DBF) as an environmental pollutant. The measurements were successfully obtained by focusing on the variation of the electrode response of EtBr, based on the competitive reaction between EtBr and DBF for the intercalating sites of DNA. The results indicated the possibility of using UV-DNA film as a sensing mechanism.     

Interaction between an ion-penetrable particle and a solid particle. II. Criteria for heterocoagulation

The potential energy of the total interaction between two spherical colloidal particles of different nature is calculated, i. e., of an ion-penetrable particle and an ion-impenetrable solid particle having a constant surface potential or constant surface charge density. The criteria for heterocoagulation are derived. The obtained results suggest a possibility of selective coagulation in the mixed system.