CE - a multifunctional application for clinical diagnosis

CE has been used widely as an analytical tool with high separation power taking advantage of size, charge-to-size ratio, or isoelectric point of various analytes. In combination with detection methods, such as UV absorption, electrochemical detection, fluorescence, or mass spectrometry (MS), it allows the separation and detection of inorganic and organic ions, as well as complex compounds, such as polypeptides, nucleic acids, including PCR amplicons from viruses or bacteria. Recent interest in identification of biomarkers of diseases using body fluids leads to development of CE-MS techniques. These applications allowed identification of new potential biomarkers for clinical diagnosis and monitoring of therapeutic interventions. In this report, we present a technical overview of various CE techniques and discuss their applications in clinical medicine.     

Determination of hydroxybupropion in human serum for routine therapeutic drug monitoring in psychiatry: A tool for dose‐individualization in treatment with bupropion

Therapeutic drug monitoring (TDM) has become a clinical routine in psychiatry. Nevertheless, for bupropion there is only one method available that is suitable for routine use. However, it involves a complex sample clean‐up. Owing to the instability of bupropion in serum, the main and active metabolite hydroxybupropion was chosen as the target substance. Therefore, a simple and robust high‐performance liquid chromatography method for the quantification of hydroxybupropion in serum was developed and validated. A volume of 30 μL serum was used for easy sample clean‐up, based on protein precipitation with acetonitrile followed by online solid‐phase extraction. As hydroxybupropion was present in high serum concentrations, UV detection was possible. Owing to the commonly available instrumentation, the method could easily be integrated in routine TDM. The newly developed method was validated following the guidelines for bioanalytical method validation of the European Medicines Agency and US Food and Drug Administration. The lower limit of quantification was 100 ng/mL (0.391 μm ) and linearity was shown between 100 and 2500 ng/mL. Intraday and interday precision ranged from 1.17 to 6.79% and from 6.07 to 9.41%, respectively. Intraday and interday accuracy ranged from 89.97 to 110.86% and from 95.05 to 101.2%. The method was shown to be selective, accurate and precise. Additionally, the method was successfully implemented in the therapeutic drug monitoring laboratory of the Department of Psychiatry, Psychosomatics and Psychotherapy at the University Hospital of Würzburg, Germany. Six months of routine analysis showed a rather low correlation between applied dose and serum concentration and therefore the necessity of TDM for dose‐individualization in the treatment with bupropion.     

Soil water balance in the Lake Chad Basin using stable water isotopes and chloride of soil profiles

ABSTRACT

The Lake Chad Basin (LCB) is an endorheic transboundary catchment highly vulnerable to drought. For effective groundwater management, recharge areas need identification and replenishment quantification. At present, little research exploring unsaturated zone water flow processes and groundwater recharge are available. In this study, 12 vertical soil profiles were analysed for stable water isotopes and chloride concentration to estimate evaporation and groundwater renewal. Most δ¹⁸O and δ²H isotope profiles reveal typical arid environment patterns, with maximum enrichment at depths between 2.5 and 20?cm and depletion towards the surface (atmospheric influence) and depth (mixing and diffusion). Average annual dry season evaporation rates in Salamat and Waza Logone range from 5 to 30?mm, in Bahr el Ghazal and Northern Lake Chad from 14 to 23?mm. According to the chloride mass balance (CMB), the average annual recharge rate is estimated between 3 and 163?mm in Salamat and Waza Logone and less than 1 mm in Bahr el Ghazal and Northern Lake Chad. Based on the CMB results, potential recharge sites were identified, while estimated soil evaporation corresponds to plant water use at the initial growing stage, which is an important component in irrigation water management.     

A structural influence on the electrical double-layer characteristics of Al4C3-derived carbon

Several carbon materials were produced by reacting aluminum carbide with chlorine gas at different temperatures (400–900 °C). Chlorination temperature and porosity values showed the inversely related trends whereby the graphitization degree rises with the chlorination temperature. Electrochemical measurements performed in three-electrode test cells with 1.0-M Et₃MeNBF₄ electrolyte revealed that the changes in porosity parameters and the degree of graphitization are in good correlation with specific capacitance values. Capacitance depends on the structure of carbon and varies in studied chlorination range from 109 to 60 F g⁻¹ and from 114 to 64 F g⁻¹ for the negatively and positively charged electrode materials, respectively. An exceptionally low capacitance was observed for the material produced at 700 °C that was explained by the multiwall carbon nanobarrels and the highly ordered curved graphitic flakes, which have low specific surface and possess the relatively low specific surface-related capacitance.     

Determination of aflatoxin B1 in alcoholic beverages: comparison of one- and two-photon-induced fluorescence

The qualitative and quantitative analysis of aflatoxin B₁ in a model system (water/ethanol), in different wines and in beer using one- and two-photon-induced fluorescence is discussed. The absorption and fluorescence properties of aflatoxin B₁ depend on the solvent and pH. The two-photon-absorption cross-section was calculated for aflatoxin B₁ in beer and wine (σ ₂ ∼ 25 GM) for excitation at 720 nm. A comparison of the one- and two-photon- induced fluorescence results showed that the disturbance due to background emission originating from matrix constituents is significantly reduced under two-photon-excitation conditions. The limit of detection for the one- and two-photon-induced fluorescence was determined.     

Reactivity and properties of [-O-Bi(III...)O=Mo-]n chains

A coordination polymer [Cp(O)2Mo-O-Bi(o-tolyl)2]n, II, containing Mo-O-Bi and Mo=O...Bi moieties was investigated with respect to its behavior in contact with OH- and Cp2MoH2 and as potential single source precursor in the polyol method. It turned out that hydroxide as a base breaks up the polymer to yield CpMoO3- and (o-tolyl)2BiOH. The latter polymerizes to give the coordination polymer [(o-tolyl)2BiOH]n, 1. Alternatively, 1 can be prepared by reacting [(o-tolyl)2Bi(hmpa)2]SO3CF3 with NBu4OH/H2O in thf/water. If, however, NBu4OH/MeOH is used in dichloromethane as the solvent, the (o-tolyl)2BiOH formed intermediately undergoes methanolysis, and finally, [(o-tolyl)2BiOMe]n, 3, is isolated. Although 1 and 3 are very similar compounds, their crystal structures differ significantly: while the structure of 1 is dominated by secondary bonding leading to seesaw-type coordination geometries around the Bi centers, the Bi atoms in 3 are coordinated in a distorted tetrahedral fashion, and secondary bonding plays only a minor role. If 1 is dissolved in a nonpolar, nonprotic solvent, condensation reactions occur immediately leading to [(o-tolyl)2BiOBi(o-tolyl)2], 2, which can be obtained on a preparative scale this way. Compound 3 which can be prepared in good yields may prove to be a useful starting material in bismuth chemistry. Here, it was shown to react with molybdocene dihydrides to provide stable Bi-substituted molybdocene monohydrides [(R)Cp2Mo(H)(Bi(o-tolyl)2)] (R = Me 4, R = H 5); compounds of that type were identified in solution before but had so far eluded isolation. Compound 4, whose crystal structure is discussed, also forms when II is treated with methylated molybdocene dihydride. This obviously leads to the formation of Mo-Bi bonds (--> 4), as well as Mo-OH units, which undergo condensation reactions leading to Mo-O-Mo moieties (i.e., [Cp2Mo2O5] is formed as a byproduct). The use of II as precursor in the polyol method successfully led to bismuthmolybdate nanoparticles (accompanied by crystallites); however, no single phase is obtained, but biphasic materials consisting of Bi(2)Mo2O9 and Bi2MoO6, whose ratio can be determined by the choice of the hydrolyzing reagent, are formed instead. One of these materials proved to be capable of sensing EtOH selectively at elevated temperatures.     

Island formation and manipulation of prochiral azobenzene derivatives on Au(111)

Based on previous work with very similar azobenzene derivatives, this study of para-TBA (2,2',5,5'-tetra-tert-butylazobenzene) molecules aims to identify single intact molecules and investigate their adsorption behavior on a Au(111) surface. The molecules are found to be mobile on the surface at the deposition temperature, leading to highly ordered and enantiomerically pure molecular islands. Voltage pulses between the surface and the tip of a scanning tunneling microscope are used to change the chirality of the adsorbate molecules. On the Cu(111) surface instead, single molecules are found on the terraces, which points to a stronger molecule-substrate interaction.     

Encapsulation dehydration colligative cryoprotective strategies and amplified fragment length polymorphism markers to verify the identity and genetic stability of euglenoids following cryopreservation

An encapsulation/dehydration procedure was developed for Euglena gracilis Klebs as a 'model alga' to examine various cryoprotective regimes combined with controlled rate cooling to cryopreserve other Euglenoid taxa. Cryoprotective variables were optimised to enable reproducible growth following a combination of alginate encapsulation, sucrose osmotic dehydration, air desiccation, methanol treatment, cooling to -40 degrees C and plunging into liquid nitrogen (LN). Amplified Fragment Length Polymorphism (AFLP) analysis was adapted to: (i) verify algal identity by discriminating between different Euglenoids and (ii) examine the genetic stability of algal cultures prior to various stages of cryoprotective treatments and following exposure to LN. AFLPs were highly reproducible (> 99%) as reliable diagnostic markers, where a single DNA fragment change accounted for -0.4% of the detectable variation in an AFLP pattern. AFLP changes were detected in cryoprotective treatments following LN exposure. Successive stages of the dehydration and desiccation treatments did not accumulate AFLP changes indicating these are random events.