Identification and separation of saxitoxins using hydrophilic interaction liquid chromatography coupled to traveling wave ion mobility‐mass spectrometry

The aim of this work was to develop a reliable and efficient analytical method to characterise and differentiate saxitoxin analogues (STX), including sulphated (gonyautoxins, GTX) and non‐sulphated analogues. For this purpose, hydrophilic interaction liquid chromatography (HILIC) was used to separate sulphated analogues. We also resorted to ion mobility spectrometry to differentiate the STX analogues because this technique adds a new dimension of separation based on ion gas phase conformation. Positive and negative ionisation modes were used for gonyautoxins while positive ionisation mode was used for non‐sulphated analogues. Subsequently, the coupling of these three complementary techniques, HILIC‐IM‐MS, permitted the separation and identification of STX analogues; isomer differentiation was achieved in HILIC dimension while non‐sulphated analogues were separated in the IM‐MS dimension. Additional structural characteristics concerning the conformation of STXs could be obtained using IM‐MS measurements. Thus, the collision cross sections (CCS) of STXs are reported for the first time in the positive ionisation mode. These experimental CCSs correlated well with the calculated CCS values using the trajectory method. Copyright © 2015 John Wiley & Sons, Ltd.     

A simple slurry consolidometer designed for the estimation of the consistency limits of soils

An inexpensive slurry consolidometer design is described that uses porous polyethylene as the permeable barrier for sample dewatering (maximum effective stress of 200 kPa) and permits monitoring of sample pore-water pressures less than 100 kPa with a portable pressure transducer. The instrument is applied in this study to the consolidation-based estimation of the Atterberg soil consistency limits of both agricultural soils and till and glaciolacustrine materials (clay fraction predominantly Ca-saturated illites) sampled from sonic boreholes. All soils originated from southwestern Ontario, Canada. With the normally consolidated (virgin) compression line expressed as a w(logσ') function, the A.S.T.M. liquid and plastic limits of the borehole soils were found to occupy relatively fixed positions on the VCL at mean effective stresses of about 61 kPa and 0.42 MPa, respectively. Marginally plastic and non-plastic soils could be distinguished as having compression line slopes approaching zero. The effective stress at the liquid limit decreased logarithmically from 61 kPa with increasing organic carbon content in the agricultural soils. Consolidated slurries of all soils investigated that were clearly plastic exhibited a mean drop-cone penetration depth of approximately 13 mm at the A.S.T.M. liquid limit, a significant departure from the British Standard of 20 mm. Slurry consolidation can be used as a sample preparation method for measurement of the liquid limit by the drop-cone or one-point A.S.T.M. procedures. It has also shown potential as a procedural alternative for the estimation of both test indices, mostly for geotechnical applications. It is probable that this unified test protocol must be recalibrated for soils where the dominant clay minerals and saturating bases are different from those in this study.     

Copper(I) catalyzed regioselective asymmetric alkoxyamination of aryl enamide derivatives

The copper(I) catalyzed reaction of an enamide with an iminoiodane, in the presence of an alcohol, triggers the direct alkoxyamination of the double bond. This transformation represents a straightforward access to α-amino aminals in a completely regio- and diastereoselective manner. Use of a chiral Box ligand allows this reaction to be carried out in an enantioselective fashion.     

Tandem postsynthetic modification of metal-organic frameworks using an inverse-electron-demand Diels-Alder reaction

A postsynthetic modification (PSM) scheme for metal-organic frameworks (MOFs) has been developed using a tetrazine-based "Click" reaction. It was found that the efficacy of this modification procedure was dependent on the MOF topology and, in the case of an isoreticular MOF (IRMOF) system, required the formation of a mixed-ligand IRMOF with a suitable ratio of 1,4-benzenedicarboxylate (BDC) and an olefin-tagged BDC derivative. On the basis of the versatile use of tetrazine "Click" chemistry in bioconjugate chemistry, we expect that this scheme will prove to be a useful reaction for preparing functionalized materials, including MOFs.     

Development of a convenient synthetic route to aminochromenes via Buchwald C-N coupling

A convenient new synthetic route to p-aminophenylaminobenzo- and naphthopyrans was developed via palladium-catalyzed C-N coupling. It was demonstrated that novel targeted aminoderivatives reveal photochromic properties. The structure of intermediate p-nitrophenylaminochromenes was confirmed by X-ray crystallographic analysis.     

A FLUORESCENCE IMAGING DEVICE FOR ENDOSCOPIC DETECTION OF EARLY STAGE CANCER – INSTRUMENTAL and EXPERIMENTAL STUDIES

Abstract Visible detection of early stage cancer labelled with the fluorescing porphyrin mixture of dihematoporphyrin-ether and dihematoporphyrin-ester (DHE) is often limited by a high and inhomogeneously distributed level of autofluorescence. A new imaging method for reducing autofluo-rescence is described. The method uses alternating fluorescence excitation with laser light in the violet and blue spectral ranges. Subtraction of the corresponding fluorescence images results in contrast enhancement due to an effective reduction in the autofluorescence contribution. A prototype version of a highly sensitive fluorescence imaging device including a modified krypton ion laser, an image-intensified solid-state TV-camera, a digital image-processing system, and video recording and monitoring has been developed.
Experiments performed with this fluorescence imaging system on a tumorous dog bladder showed that a dose of 0.2 mg DHE kg⁻¹ body wt, which is far below the dose administered for photodynamic therapy (2-5 mg kg⁻'body wt), is sufficient to give a high-contrast fluorescence image. The corresponding excitation power density was about 1 W m⁻². Photobleaching of DHE was observed during fluorescence detection at excitation power densities exceeding 1 kW m⁻². At these high excitation levels DHE fades out nearly completely within 0.25 min.     

Surfactant effects on pH-controlled synthesis of nickel hydroxides

The aim of the present work is to determine at 60 °C, the influence of the specific nature of nickel salt and pH on nickel hydroxide features such as crystallographic structure and morphology. Within the range 8 ≤ pH ≤ 11.5, a home-made nickel functionalized surfactant, nickel di-dodecylsulfate Ni(C₁₂H₂₅SO₄)₂ is compared to usual salts (nickel nitrate Ni(NO₃)₂ and nickel sulfate NiSO₄). In both cases, a sharp transition appears for pH about 10. In the classic salt case, the transition mainly affects morphology, that could be evidenced by the crosschecking of complementary techniques as SEM and nitrogen gas adsorption. For pH < 10, β-Ni(OH)₂ platelets are yielded, whereas more basic conditions lead to randomly aggregated nano-grains of badly crystallized β hydroxide. Inversely, by employing the functionalized surfactant, 2D morphology is maintained in the whole pH-range, but the crystal structure is pH-controlled ( phase with interlamellar dodecylsulfate for pH ≤ 9.5, and β phase for pH ≥ 10.5).     

Functionalization of aminocrown ethers with [2H]-chromene units by Buchwald-Hartwig C-N coupling for constructing of photoswitchable molecular devices

Functionalization of the diaminodibenzocrown ethers with 2H-[1]benzopyrane and 3H-naphtho[2,1-b]pyrane units by Buchwald-Hartwig C-N coupling was developed. It is demonstrated that the novel molecule possesses photochromic properties that can be modified by the complex formation process.     

Qualitativer und quantitativer Vergleich von Chromatogrammen unter Verwendung eines Rechners

Zusammenfassung Ein Computerprogramm zum Vergleich von Probe- mit Standardpeaks wird beschrieben. Die natürlichen Fehler eines Chromatographen, wie Temperatur- oder Druck-schwankungen, werden durch eine fortlaufende Anpassung der Erkennungsfenster ausgeglichen. Diese Methode gestattet sehr schmale Zeitfenster und verhindert größtenteils Doppelidentifikationen. Eine quantitative Analyse beginnt nach der Peakzuordnung. Jeder identifizierte Probepeak wird einem Ausreißertest nach Nalimov unterzogen. Zuletzt wird ein Vergleich der Flächen benützt, um eine quantitative Beziehung zwischen Probe und Standard zu erreichen.

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Qualitative and quantitative comparison of chromatograms by computer

Summary A computer program is described which allows the comparison of sample peaks with those of a standard. The errors produced by the chromatograph due to instability of inlet pressure or temperature are corrected by a consecutive adaption of time-windows of standard peaks. This method makes it possible to keep the time-windows for peak identification very small and to eliminate double identifications to a great extent. Quantitative analysis follows peak identification. Each sample peak has to pass a Nalimov test. A comparison of peak areas is finally used to establish a quantitative relation between sample and standard.