Analytical Determination of 1,6-Anhydro-β-D-Glucopyranose and Kinetic Studies Under Hydrothermal Conditions

1,6-Anhydro-β-D-giucopyranose was identified for the first time in aqueous solutions obtained by hydrothermolysis of cellulosic matter. The identification and quantitative determination of the 1,6-anhydro-β-D-glucopyranose, as well as of further degradation and conversion products, was accomplished by means of HPLC. For kinetic studies, 1,6-anhydro-β-D-glucopyranose was degraded in aqueous solution under hydrothermal conditions in the range of 200-240°C. A kinetic model covering both formation and decomposition of 1,6-anhydro-β-D-glucopyranose is proposed.     

A method for accurate in silico modeling of ultrasound transducer arrays

This paper presents a new approach to improve the in silico modeling of ultrasound transducer arrays. While current simulation tools accurately predict the theoretical element spatio-temporal pressure response, transducers do not always behave as theorized. In practice, using the probe’s physical dimensions and published specifications in silico, often results in unsatisfactory agreement between simulation and experiment. We describe a general optimization procedure used to maximize the correlation between the observed and simulated spatio-temporal response of a pulsed single element in a commercial ultrasound probe. A linear systems approach is employed to model element angular sensitivity, lens effects, and diffraction phenomena. A numerical deconvolution method is described to characterize the intrinsic electro-mechanical impulse response of the element. Once the response of the element and optimal element characteristics are known, prediction of the pressure response for arbitrary apertures and excitation signals is performed through direct convolution using available tools. We achieve a correlation of 0.846 between the experimental emitted waveform and simulated waveform when using the probe’s physical specifications in silico. A far superior correlation of 0.988 is achieved when using the optimized in silico model. Electronic noise appears to be the main effect preventing the realization of higher correlation coefficients. More accurate in silico modeling will improve the evaluation and design of ultrasound transducers as well as aid in the development of sophisticated beamforming strategies.     

A quantitative infrared spectral database of hazardous air pollutants

Open-path monitoring of the atmosphere using Fourier transform infrared spectrometry has recently become a useful real-time in situ analytical technique. The U.S. Environmental Protection Agency (EPA) is currently formulating Method TO-16, a protocol for infrared remote sensing of the hazardous air pollutants (HAPs) identified in EPA’s Clean Air Act of 1990. To support infrared based sensing technologies, the National Institute of Standards and Technology (NIST) is currently developing a standard quantitative spectral database of the HAPs based on gravimetrically prepared samples. This paper presents the protocol used to prepare the gravimetric mixtures and initial results. Received: 6 June 1997 / Revised: 4 August 1997 / Accepted: 7 August 1997     

Calibration and uncertainty assessment for certified reference gas mixtures

The weighted least squares method to build an analysis function described in ISO 6143, Gas analysis—Comparison methods for determining and checking the composition of calibration gas mixtures, is modified to take into account the typically small number of instrumental readings that are obtained for each primary standard gas mixture used in calibration. The theoretical basis for this modification is explained, and its superior performance is illustrated in a simulation study built around a concrete example, using real data. The corresponding uncertainty assessment is obtained by application of a Monte Carlo method consistent with the guidance in the Supplement 1 to the Guide to the expression of uncertainty in measurement, which avoids the need for two successive applications of the linearizing approximation of the conventional method for uncertainty propagation. The three main steps that NIST currently uses to certify a reference gas mixture (homogeneity study, calibration, and assignment of value and uncertainty assessment), are described and illustrated using data pertaining to an actual standard reference material.     

Mass spectrometry imaging with high resolution in mass and space (HR<Superscript>2</Superscript> MSI) for reliable investigation of drug compound distributions on the cellular level

Mass spectrometry (MS) imaging is a versatile method to analyze the spatial distribution of analytes in tissue sections. It provides unique features for the analysis of drug compounds in pharmacokinetic studies such as label-free detection and differentiation of compounds and metabolites. We have recently introduced a MS imaging method that combines high mass resolution and high spatial resolution in a single experiment, hence termed HR² MS imaging. In the present study, we applied this method to analyze the spatial distribution of the anti-cancer drugs imatinib and ifosfamide in individual mouse organs. The whole kidney of an animal dosed with imatinib was measured at 35 μm spatial resolution. Imatinib showed a well-defined distribution in the outer stripe of the outer medulla. This area was analyzed in more detail at 10 μm step size, which constitutes a tenfold increase in effective spatial resolution compared to previous studies of drug compounds. In parallel, ion images of phospholipids and heme were used to characterize the histological features of the tissue section and showed excellent agreement with histological staining of the kidney after MS imaging. Ifosfamide was analyzed in mouse kidney at 20 μm step size and was found to be accumulated in the inner medulla region. The identity of imatinib and ifosfamide was confirmed by on-tissue MS/MS measurements. All measurements including mass spectra from 10 μm pixels featured accurate mass (≤2 ppm root mean square) and mass resolving power of R = 30,000. Selected ion images were generated with a bin size of ∆m/z = 0.01 ensuring highly specific information. The ability of the method to cover larger areas was demonstrated by imaging a compound in the intestinal tract of a rat whole-body tissue section at 200 μm step size. The described method represents a major improvement in terms of spatial resolution and specificity for the analysis of drug compounds in tissue sections.     

Determining Dynamic Properties of Elastomer-Dampers by Means of Impact Testing

Experimental Mechanics - Damping elements made of elastomer materials are used in almost every mechanical system to prevent damage to components caused by impact-like excitations and the resulting...     

PAMAM dendrimer hydrogel film—biocompatible material to an efficient dermal delivery of drugs

We report the preparation, characterization, and drug release kinetics of a pH-responsive hydrogel film from a dendrimer megamer. The megamer (GP32) is a three-dimensional reticulated structure with a mean diameter of 71.16 nm (PDI 0.150) and was prepared by the reaction between Poly(amidoamine) generation4 (PAMAM G4) dendrimer and glutaraldehyde (G:P molar ratio 32). The crosslinking units in the megamer are provided mainly by the bicyclic dimer 2-hydroxy-3,4,4a,7,8,8a–hexahydro-2H-chromene-6-carbaldehyde as determined by high-resolution (800 MHz) ¹H NMR and FTIR. The hydrogel film (F[GP32]) is formed upon evaporation of a methanolic solution of the megamer and has a high degree of organization and homogeneity. Further crosslinking with glutaraldehyde (CLF[GP32]) enhanced the mechanical properties of the hydrogel film. The chemical constitution and unique megamer architecture enable the hydrogel film to carry both lipophilic and hydrophilic substances. The film did not cause any dermal irritation or clinical signs of toxicity in tests on rabbits, allowed for a sustained release of ketoprofen and played an important role in the process of drug delivery into the receptor medium. This performance taken together with the absence of toxicity makes this hydrogel film a good choice for dermal sustained drug release.

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Comparison of liquid-liquid partition, HS-SPME and static HS GC/MS analysis for the quantification of (-)-linalool in human whole blood samples

The aim of this investigation was to develop a fast and convenient method for the determination of (-)-linalool in human whole blood to facilitate pharmacokinetic studies. Analytical protocols were elaborated for three different GC/MS sampling techniques, i.e., static headspace (s-HS), headspace solid phase micro extraction (HS-SPME), and liquid-liquid partition. In principle, all tested methods were feasible, but s-HS had the greatest benefit because of the easy handling of the blood samples and its short analysis time. For s-HS two different incubation temperatures were tested (40 degrees C and 60 degrees C). The limit of detection was slightly lower when samples were incubated at 60 degrees C, but the same quantitative results were achieved using alpha-terpineol as internal standard. An accurate and sensitive method for the quantification of (-)-linalool in blood samples after either inhalation or percutaneous application, as well as pharmacokinetic data are presented.     

Monolithic poly(p-methylstyrene-co-1,2-bis(p-vinylphenyl)ethane) capillary columns as novel styrene stationary phases for biopolymer separation

Novel monolithic capillary supports (200 microm I.D.) were prepared by polymerisation of methylstyrene (MS) and 1,2-bis(p-vinylphenyl)ethane (BVPE) as a crosslinker in the presence of inert diluents (porogens). These polymeric reversed-phases (MS/BVPE) showed excellent mechanical stability and minimised swelling in organic solvents. The chromatographic potential of monolithic MS/BVPE as a stationary phase for micro-high-performance liquid chromatography (mu-HPLC) was investigated by the separation of proteins and peptides applying reversed-phase (RP) and nucleic acids applying ion-pair reversed-phase (IP-RP) conditions. The permeability and chromatographic efficiency of the capillary columns were found to be highly influenced by the total monomer to porogen content as well as by the microporogen nature and its ratio. In the course of these optimisation studies, monoliths covering a broad permeability range were fabricated. The application of volumetric flow rates up to 200 microl/min allowed swift resolution of proteins, while smaller biomolecules were successfully separated at a higher overall porosity. A protein test mixture containing ribonuclease A, cytochrome c, alpha-lactalbumin, beta-lactoglobulin B and ovalbumin was thus baseline separated in 35s, a homologous series of phosphorylated oligothymidylic acids [d(pT)12-18] in less than 2 min.     

Depth profile studies of ZrTiN coatings by laser ablation inductively coupled plasma mass spectrometry

The feasibility of depth profiling was studied by using a 193-nm ArF* excimer laser ablation system (GeoLas, MicroLas, Goettingen, Germany) with a lens array-based beam homogenizer in combination with an ICP-QMS Agilent 7500. Two ablation cells (20 and 1.5 cm³) were compared at the laser repetition rate of 1 Hz, laser beam energy of 135 mJ and the carrier gas flow rate 1.5 L min^–1 He + 0.78 L min^–1 Ar. The ablation cell dimensions are important parameters for signal tailing; however, very small cell volumes (e.g. 1.5 cm³) may cause memory effects, which can be probably explained by dominant inertial losses of aerosol on cell walls with its delayed mobilization. The 20-cm³ ablation cell seems to be appropriate for depth profiling by continuous single-hole drilling. The study of the influence of the pit diameter magnitude on the waning and emerging signals under small crater depth/diameter aspect ratios, which range between 0.75 and 0.0375 for the 3-m-thick coatings and pit diameters 4–80 m, revealed that the steady-state signals of pure coating and pure substrate (out of interface) were obtained at crater diameters between 20 and 40 m. Depth resolution defined by means of slopes of tangents in the layer interface region depend on the pit diameter and has an optimum value between 20 and 40 m and gives 0.6 m for the 20-m pit. In-depth variation of concentration of coating constituent (Ti) was proved to be almost identical with two different laser/ICP systems.Viktor Kanický performed this work while on leave at ETH Zurich