Role of polar and apolar moieties in water adsorption by humic acids under arid conditions

Journal of Thermal Analysis and Calorimetry - In arid soils, humic acids (HAs) are used as amendments to improve water uptake from the atmosphere. This method of harvesting water involves several...     

In-bone protein digestion followed by LC-MS/MS peptide analysis as a new way towards the routine proteomic characterization of human maxillary and mandibular bone tissue in oral surgery

Proteomic characterization of alveolar bones in oral surgery represents an analytical challenge due to their insoluble character. The implementation of a straightforward technique could lead to the routine use of proteomics in this field. This work thus developed a simple technique for the characterization of bone tissue for human maxillary and mandibular bones. It is based on the direct in-bone tryptic digestion of proteins in both healthy and pathological human maxillary and mandibular bone samples. The released peptides were then identified by the LC-MS/MS. Using this approach, a total of 1120 proteins were identified in the maxillary bone and 1151 proteins in the mandibular bone. The subsequent partial least squares–discrimination analysis (PLS-DA) of protein data made it possible to reach 100% discrimination between the samples of healthy alveolar bones and those of the bone tissue surrounding the inflammatory focus. These results indicate that the in-bone protein digestion followed by the LC-MS/MS and subsequent statistical analysis can provide a deeper insight into the field of oral surgery at the molecular level. Furthermore, it could also have a diagnostic potential in the differentiation between the proteomic patterns of healthy and pathological alveolar bone tissue. Data are available via ProteomeXchange with the identifier PXD026775.     

Preparation of α-terpineol and perillyl alcohol using zeolites beta

The preparation of α-terpineol by direct hydration of limonene catalyzed by zeolites beta was studied. The same catalyst was used to prepare perillyl alcohol by isomerization of β-pinene oxide in the presence of water. The aim was to optimize the reaction conditions to achieve high conversions of starting material and high selectivity to the desired products. In the case of limonene, it was found that the highest selectivity to α-terpineol was 88% with conversion of 36% under the conditions: 50 wt% of catalyst beta 25, 10% aqueous acetic acid (10 mL) (volume ratio limonene:H₂O?=?1:4.5), temperature 50 °C, after 24 h. In the case of β-pinene oxide, it was found that the highest selectivity to perillyl alcohol, which was 36% at total conversion, was obtained in the reaction under the following conditions: dimethyl sulfoxide as solvent (volume ratio β-pinene oxide:DMSO?=?1:5), catalyst beta 25 without calcination (15 wt%), demineralized water (molar ratio β-pinene oxide:H₂O?=?1:8), temperature 70 °C, 3 h. The present study shows that the studied reactions are suitable for the selective preparation of chosen compounds.

     

Application of Non‐Stop‐Flow Differential Pulse Voltammetry at a Tubular Detector of Silver Solid Amalgam for Electrochemical Determination of Lomustine (CCNU)

An application of the flow differential pulse voltammetry with tubular detector based on silver solid amalgam for determination of antineoplastic drug lomustine in pharmaceutical preparations is presented. The highest sensitivity was obtained in [0.10 mol dm^?3 MES; 2.00 mol dm^?3 NaCl; pH 6.0]:EtOH (9 : 1) with flow rate 0.50 mL min^?1, and the magnitude of the modulation amplitude ?0.070 V. The calibration dependence was linear in the range 1×10^?6–1 × 10^?4 mol dm^?3 (R²=0.999). The limit of detection was 1.5×10^?7 mol dm^?3. This method was successfully used for determination of lomustine in real samples of chemotherapy drug CeeNU Lomustine 40 mg.     

Electrochemical Biosensors Based on Enzymatic Reactor of Silver Solid Amalgam Powder for Measurements in Flow Systems

An enzymatic reactor based on silver solid amalgam powder was suggested as the main part of biosensors in flow systems for the first time. Biosensors were tested with following enzymes: ascorbate oxidase, glucose oxidase, catalase, tyrosinase and laccase. The current response of each biosensor was optimized with respect to the detection potential, flow rate, the injection and reactor volume. Relative standard deviation for detection with the studied enzymes was found to be in the range of 0.81–2.1 %. The biosensor with the ascorbate oxidase reactor was used for determination of ascorbic acid in the vitamin tablets Celaskon.     

Thermal analysis of polyaniline poly(N-vinylpyrrolidone)-stabilized dispersions

The polyaniline dispersions stabilized with poly(N-vinylpyrrolidone) (PANI/PVP) were synthesized by oxidative polymerization with different mass ratios of PANI and PVP and different molar concentrations of the components in the polymerization mixture. The composite powders prepared from colloidal PANI/PVP dispersions were characterized by thermogravimetry and differential thermal analysis. The change in the ratio of PANI and PVP as well as the starting molar concentrations of aniline hydrochloride and oxidant has influence on the resulting properties of the dispersions. Concerning the doping, the results show that PANI/PVP powders are stable up to approximately 160 °C. Degradation of polymer chains starts at temperatures above 250 °C. The PANI/PVP composite powders with lower content of PANI exhibit slightly higher thermal stability. Further, colloidal PANI/PVP dispersions were screen-printed on aluminum foil for infrared spectroscopic characterization and on poly(ethylene terephthalate) foil for electrical measurements. The sheet resistance of printed layers measured by two-point probe was of the order of tens to thousands of kΩ sq^?1. The influence of both the change in the composition and the drying temperature is discussed.     

The Assembly‐Disassembly‐Organization‐Reassembly Mechanism for 3D‐2D‐3D Transformation of Germanosilicate IWW Zeolite

Hydrolysis of germanosilicate zeolites with the IWW structure shows two different outcomes depending on the composition of the starting materials. Ge‐rich IWW (Si/Ge=3.1) is disassembled into a layered material (IPC‐5P), which can be reassembled into an almost pure silica IWW on treatment with diethoxydimethylsilane. Ge‐poor IWW (Si/Ge=6.4) is not completely disassembled on hydrolysis, but retains some 3D connectivity. This structure can be reassembled into IWW by incorporation of Al to fill the defects left when the Ge is removed.     

Zeolites with Continuously Tuneable Porosity

Zeolites are important materials whose utility in industry depends on the nature of their porous structure. Control over microporosity is therefore a vitally important target. Unfortunately, traditional methods for controlling porosity, in particular the use of organic structure‐directing agents, are relatively coarse and provide almost no opportunity to tune the porosity as required. Here we show how zeolites with a continuously tuneable surface area and micropore volume over a wide range can be prepared. This means that a particular surface area or micropore volume can be precisely tuned. The range of porosity we can target covers the whole range of useful zeolite porosity: from small pores consisting of 8‐rings all the way to extra‐large pores consisting of 14‐rings.     

Determination of mercury species using thermal desorption analysis in AAS

Analytical aspects of the determination of inorganic mercury (Hg) species by thermal desorption followed by atomic absorption spectrometry (AAS) detection were investigated in this work. Characteristic Hg release curves of the following species were observed: Hg⁰, HgCl₂, HgO, HgSO₄, HgS, and the Hg bound to humic acids. Particular attention was dedicated to the thermal stability and change of bond of Hg⁰ in the following matrices: sand, kaolinite, granite, peat, power plant ash, and soil. The bond of elemental Hg in environmental materials was described on basis of this experiment. Contaminated soil samples from two locations in the Czech Republic were investigated by thermal desorption analysis. Afterwards, the contents of volatile and plant-available Hg in the studied samples were determined. The determination of Hg⁰ using the thermal method was related to the results of liquid sequential extraction. The development of Hg speciation and the stability of Hg were assessed on basis of the data obtained. Thus, the analytical procedure used is a suitable tool for the study of inorganic Hg species in contaminated soils.