Sensitive biomonitoring of phthalate metabolites in human urine using packed capillary column switching liquid chromatography coupled to electrospray ionization ion-trap mass spectrometry

A rapid and sensitive method for the determination of the phthalate monoesters monoethyl phthalate (MEP), monobutyl phthalate (MBP), monobenzyl phthalate (MBzP) and monoethylhexyl phthalate (MEHP), in human urine, using packed capillary column liquid chromatography coupled to electrospray quadrupole-ion trap mass spectrometry (ESI-QITMSⁿ) has been developed. Sample volumes of 200 L of deconjugated and diluted urine were loaded onto a precolumn of 30 mm×0.32 mm I.D. packed with Hypercarb 5 m particles, using a sample carrier consisting of acetonitrile/water (15/85, v/v, adjusted to pH 2 using HCl) with a flow rate of 20 L/min. Backflushed elution onto a 100 mm×0.32 mm I.D. analytical column packed with 5 m Hypercarb particles was conducted using a tetrahydrofuran/water gradient where both solvents contained 10 mM ammonium acetate, at a flow rate of 4 L/min. Determination of the monophthalates was achieved within 8 min. Ionization was performed in the negative mode and the analytes were observed as [M-H]^– at m/z=193.1, 221.1, 255.1 and 277.0 for MEP, MBP, MBzP and MEHP, respectively. Quantification was performed in the multiple reaction monitoring (MRM) mode monitoring the fragments at m/z=121.1, 177.0, 183.0 and 233.0 for MEP, MBP, MBzP and MEHP, respectively. The method was validated over the concentration range 2.5–125 ng/mL in pretreated urine samples, corresponding to 25–1250 ng/mL untreated urine, yielding correlation coefficients in the range 0.996–0.999. The within-assay (n=6) and between-assay (n=6) repeatabilities were in the range 4.0–18% and 4.8–15% RSD, respectively. The mass limits of detection were in the range 32–70 pg, corresponding to concentration limits of detection of 1.6–3.5 ng/mL of untreated urine.     

A rod-like polymer containing (Ru(terpy)2) units prepared by electrochemical coupling of pendant thienyl moieties

A new rod-like coordination polymer consisting of (Ru-(terpy)2) motifs bridged by bithiophene units has been prepared by electrochemical polymerisation in acidic organic medium.     

Conformational analysis by solid-state NMR and its application to restrained structure determination from powder diffraction data

Solid-state NMR is used to dramatically improve the efficiency and reliability of molecular crystal structure determination from X-ray powder diffraction data.     

Thermische Ausdehnung von Metallen bei tiefen Temperaturen

The thermal expansion coefficients of the following metals in the temperature region between 1,5° and 12°K have been measured: Al, Pb, Pt, Mo, Ta, W, Mg, Cd, Re, Ti, La, Ce, Nd, Gd, Yb. Except for tantalum all the specimens were polycrystalline. Is is found in accordance with theoretical prediction that the coefficient of thermal expansionβ=1/V (?V/?T) [whereV = volume,T = temperature] at sufficiently low temperatures is composed of an electronic component varying linearly with temperature, and a lattice component varying as the cube of the temperature. The electronic component is strongly modified in the superconducting state (Pb, Ta, La). The rare earth metals Gd, Ce and Nd have negative anomalies in their expansion. These are connected with the ferro- and antiferromagnetism of these substances. The results are discussed on the basis of lattice dynamics and the theory of electrons in metals.     

Frequency doubling and tuning with KB5O8·4H2O and application to NO (A2Σ+) excitation

Frequency doubling by angle tuning with KB₅O₈·4H₂O has been investigated at 217.0–250 nm. The phase matching angle, refractive index and doubling efficiency have been measured. A first application has been made by exciting NO(A²Σ⁺) in the UV.     

A tutorial review of the basic theory for and practical aspects of aerosol chambers

A review of the theory for the separation of large droplets in aerosol chambers related to analytical spectroscopy is given. The theoretical treatment is used for discussing practical aspects and the behaviour of aerosol chambers. It is shown that the theories presented can be used for explaining the characteristics of aerosol chambers. The most likely processes describing the separation of large droplets in aerosol chambers are inertial deposition processes. Cyclone and jet impaction are the most interesting concepts for designing new types of aerosol chambers for atomic spectroscopy.     

Study of an Underexpanded Plasma Jet II. Diagnostics with Microwaves

The properties of the plasma of an underexpanded jet in air were examined by optical and by probe methods as described in a previous paper (Contrib. Plasma Phys. 27 (1987) 203). The jet was produced by an erosion plasmatron with xenon-filling operating in a single-pulse regime. Now, independent measurements of the space-time development of the electron density by microwave interferometry are described. The results of cut-off and phase shift measurements are in agreement with those obtained by probe diagnostics.     

Acylations of 1,10-dilithiophenothiazine. A new synthesis of 1-formylphenothiazine

The synthesis of 1-formyl-, 1-benzyyl-, 1-anisoyl-, and 1-nicotinyl-phenothiazines ( 1–4 ) resulting from the reaction of the corresponding amids with 1,10-dilithiophenothiazine ( 5 ) is reported. The site of attachment on 1,10-dilithiophenothiazine, based on the nature of some different acylating reagents, is also discussed.     

Model-based optimization of a preparative ion-exchange step for antibody purification

A method using a model-based approach to design and optimize an ion-exchange step in a protein purification process is proposed for the separation of IgG from a mixture containing IgG, BSA and myoglobin. The method consists of three steps. In the first step, the model is calibrated against carefully designed experiments. The chromatographic model describes the convective and dispersive flow in the column, the diffusion in the adsorbent particles, and the protein adsorption using Langmuir kinetics with mobile phase modulators (MPM). In the second step, the model is validated against a validation experiment and analyzed. In the third and final step, the operating conditions are optimized. In the optimization step, the loading volume and the elution gradient are optimized with regard to the most important costs: the fixed costs and the feed cost. The optimization is achieved by maximizing the objective functions productivity (i.e. the production rate for a given amount of stationary phase) and product yield (i.e. the fraction of IgG recovered in the product stream). All optimization is conducted under the constraint of 99% purity of the IgG. The model calibration and the analysis show that this purification step is determined mainly by the kinetics, although as large a protein as IgG is used in the study. The two different optima resulting from this study are a productivity of 2.7 g IgG/(s m3) stationary phase and a yield of 90%. This model-based approach also gives information of the robustness of the chosen operating conditions. It is shown that the bead diameter could only be increased from 15 microm to 35 microm with maximum productivity and a 99% purity constraint due to increased diffusion hindrance in larger beads.