Development of the HPLC Method for Simultaneous Determination of Lidocaine Hydrochloride and Tribenoside Along with Their Impurities Supported by the QSRR Approach

A new liquid chromatographic (LC) method for simultaneous determination of lidocaine hydrochloride (LH) and tribenoside (TR) along with their related compounds in pharmaceutical preparations is described. Satisfactory LC separation of all analytes after the liquid–liquid extraction (LLE) procedure with ethanol was performed on a C₁₈ column using a gradient elution of a mixture of acetonitrile and 0.1 % orthophosphoric acid as the mobile phase. The procedure was validated according to the ICH guidelines. The limits of detection (LOD) and quantification (LOQ) were 4.36 and 13.21 μg mL^?1 for LH, 7.60 and 23.04 μg mL^?1 for TR, and below 0.11 and 0.33 μg mL^?1 for their impurities, respectively. Intra- and inter-day precision was below 1.97 %, whereas accuracy for all analytes ranged from 98.17 to 101.94 %. The proposed method was sensitive, robust, and specific allowing reliable simultaneous quantification of all mentioned compounds. Moreover, a comparative study of the RP-LC column classification based on the quantitative structure-retention relationships (QSRR) and column selectivity obtained in real pharmaceutical analysis was innovatively applied using factor analysis (FA). In the column performance test, the analysis of LH and TR in the presence of their impurities was carried out according to the developed method with the use of 12 RP-LC stationary phases previously tested under the QSRR conditions. The obtained results confirmed that the classes of the stationary phases selected in accordance with the QSRR models provided comparable separation for LH, TR, and their impurities. Hence, it was concluded that the proposed QSRR approach could be considered a supportive tool in the selection of the suitable column for the pharmaceutical analysis.     

Determination of phthalate esters content in plastic articles: Comparison of extraction methods

Two variants of solvent extraction method (by Soxhlet and ultrasonic) for phthalate esters (DEHP) recoveries in PVC samples were compared. Solvent and extraction time for both techniques were also studied. DEHP content was quantified by GC-MS. The results obtained were compared using statistical methods (LSD test, t-test). 16-Hours DCM Soxhlet and 2-h DCM ultrasonic extraction methods were more convenient with respect to recovery, precision and practicability.     

Structural, textural and adsorption characteristics of nanosilica mechanochemically activated in different media

The structural, textural, and adsorption characteristics of mechanochemically activated (MCA) fumed silica A-300 as dry or water, ethanol, or water/ethanol-wetted powders (0.5 g of a solvent per gram of silica) in a ball mill for 1-6 h were studied in comparison with those of the initial powder. The MCA treatment enhances bulk density (ρ(b)) of the powder (from 0.045 g/cm(3) for the initial silica to 0.4 g/cm(3) for 6 h-MCA-treated water-wetted silica) depending on medium type and MCA time (t(MCA)). Stronger effects are observed for the MCA treatment of water-wetted silica than of dry or ethanol- or water/ethanol-wetted samples. The MCA treatment weakly affects the specific surface area (S(BET)). However, void (pore) size distribution, porosity, particle aggregation and size distribution in aqueous suspension, behavior of interfacial water, properties of poly(vinyl alcohol)/silica composites and adsorption of gelatin depend more strongly on the t(MCA) and ρ(b) values. Some of the observed changes in the characteristics (e.g., gelatin adsorption) depend on the ρ(b) value but are independent of the medium type used on the MCA. Other characteristics are nonlinear functions of both t(MCA) and ρ(b) values.     

Macrocyclic multicenter complexes of nickel and copper of increasing complexity

Multicenter (bi-, tri-, and tetranuclear) tetraazamacrocyclic complexes were self-assembled from Ni and Cu tetraazamacrocyclic mononuclear units and α,ω-diamines as building blocks. The structures of all compounds studied were proved by spectroscopic methods (ESI MS and NMR spectroscopy). Electrochemical experiments revealed reversible one-electron electrode processes at each of the Ni(2+) and Cu(2+) centers with formation of metal cations in oxidation state +3. Long linkers allow bi- and trinuclear complexes with noninteracting metal centers to be obtained. In the case of the short linkers (e.g. ethylenediamine) higher, trinuclear species are formed as major product. The structures of the bis- and tris-macrocyclic systems were confirmed by single-crystal X-ray diffraction. The tris-macrocyclic systems form cations in the shape of triangles partially filled with counterions and solvent molecules. The cations form positively charged layers, which interact in the crystal lattice with the neighboring negatively charged layers of anions. In solution, the trinuclear complexes exhibit strong host-guest interactions with 9,10-dimethyltriptycene due to complementarity of shape and size of this guest molecule. The association constants were determined by NMR spectroscopy and voltammetry, and very good agreement was obtained. The structural flexibility of the tetranuclear complex with long linkers allows for attractive interactions between the metal-complexing macrocycles that result in folding of the molecule. On the contrary, no folding is possible in the case of short linkers consisting of two CH(2) groups.     

Following cellulose depolymerization in paper: comparison of size exclusion chromatography techniques

The study focuses on the comparison of the results obtained by size exclusion chromatography (SEC) detection systems using multiangle laser light scattering (MALLS) and/or ultraviolet–visible (UV/VIS) detectors in analyses of cellulose in paper-based heritage objects. The commonly applied parameter for the evaluation of paper degradation stage and kinetics is weight (M _w ) average molar mass measured by SEC. The main problems addressed here are whether the parameters obtained by various techniques and calibration strategies and in various laboratories can be treated universally and what the sources of the discrepancies can be. The SEC-UV/VIS technique proved to give reproducible results as demonstrated by the interlaboratory correlations. Using various data processing methods and SEC techniques it was also shown that molar masses should only be treated relatively. The differences between the kinetic curves based on the M _w values obtained from various techniques and processed with various calibration procedures question the reliability of kinetic equations derived using the SEC results to describe the paper degradation.     

Decision trees in selection of featured determined food quality

The determination of food quality, authenticity and the detection of adulterations are problems of increasing importance in food chemistry. Recently, chemometric classification techniques and pattern recognition analysis methods for wine and other alcoholic beverages have received great attention and have been largely used. Beer is a complex mixture of components: on one hand a volatile fraction, which is responsible for its aroma, and on the other hand, a non-volatile fraction or extract consisting of a great variety of substances with distinct characteristics. The aim of this study was to consider parameters which contribute to beer differentiation according to the quality grade. Chemical (e.g. pH, acidity, dry extract, alcohol content, CO(2) content) and sensory features (e.g. bitter taste, color) were determined in 70 beer samples and used as variables in decision tree techniques. This pattern recognition techniques applied to the dataset were able to extract information useful in obtaining a satisfactory classification of beer samples according to their quality grade. Feature selection procedures indicated which features are the most discriminating for classification.     

Role of the Cluster Structure of Amorphous Fe<Subscript>67</Subscript>Cr<Subscript>18</Subscript>B<Subscript>15</Subscript> Alloy in Magnetism and in the Changing of Electron Scattering Mechanisms under the Influence of Ion (Ar<Superscript>+</Superscript>) Irradiation

The contribution of clusters of different sizes to magnetism and the switching of electron scattering mechanisms in amorphous Fe₆₇Cr₁₈B₁₅ alloy during ion Ar⁺ irradiation is studied. The cluster magnetism is found to be related to the presence of clusters of the following two types: large α-(Fe, Cr) clusters of size D = 150–250 Å and small (D = 40–80 Å) clusters in a random intercluster medium. The generation of small ferromagnetic and antiferromagnetic clusters during ion irradiation leads to the formation of cluster glass, which affects the electrical properties of the alloy and causes a magnetic frustration. The temperature dependence of the barrier height is shown to characterize the magnetic state of the alloy in low fields. On the whole, the temperature dependence of the order parameter is a universal characteristic of the system. The temperature dependence of resistivity of initial alloys in the temperature range 98–300 K (ρ(T) ∝ T²) is determined by electron scattering by quantum defects, and the transition into a ferromagnetic state is revealed when the derivative ?ρ/?T ∝ T is analyzed. The increase in resistivity and the relation ρ ∝ T^1/2 in strongly inhomogeneous samples after irradiation at a dose Φ = 1.5 × 10¹⁸ ions/cm² are caused by weak localization effects, and the transition to a ferromagnetic state becomes obvious when the derivative ?ρ/?T ∝ T^–1/2 is considered. Irradiation by fluence Φ = 3 × 10¹⁸ ions/cm2 induces a giant (twofold) increase in the alloy density, restores the ferromagnetism of large clusters, decreases the resistivity by 37%, and restores the relation ρ(T) ∝ T², which results from the overlapping of the irradiation-induced small clusters when their concentration increases and from an increase in the alloy density. The overlapping of clusters lowers the barrier height and decreases the sensitivity of the alloy to an applied field. The relation ρ(T) ∝ T² is valid for the entire temperature range T = 2–300 K because of the partial screening of the magnetic moments of large clusters by a medium having the properties of cluster glass.     

Sensitive adsorptive stripping voltammetric procedure of Imatinib determination in spiked urine samples using solid lead microelectrode

This article reports for the first time the application of solid lead microelectrode for organic compound determination. The proposed sensor was used for anticancer drug Imatinib quantification by adsorptive stripping voltammetry. Procedure of Imatinib determination was developed utilizing advantages ensured by solid lead microelectrode: reusability and durability for a long period of time and its ecological character as compared to film electrodes. The detection limit of Imatinib determination was calculated to be 1.9 × 10⁻¹⁰ mol L⁻¹. The analytical usability of the developed procedure was confirmed by acceptable recoveries of Imatinib determination in spiked urine samples.     

Bispalladium(II) Complexes of di-p-Pyrirubyrin Derivatives as Promising Near-Infrared Photoacoustic Dyes

The insertion of palladium(II) into di-p-pyrirubyrin results in mutually convertible bimetallic complexes. Post-synthetic functionalization of one of them yielded bispalladium(II) dioxo-di-p-pyrirubyrin and, after demetallation, dioxo-di-p-pyrirubyrin, introducing for the first time the α,β′-pyridin-2-one unit into the macrocyclic frame. Bispalladium(II) di-p-pyrirubyrin 6 , bispalladium(II) dioxo-di-p-pyrirubyrin 9 , and dioxo-di-p-pyrirubyrin 10 absorb and emit light around 1000 nm and are characterized by high photostability. Thus, they are promising candidates for near-infrared photoacoustic dyes, ideally targeting ( 9 ) the wavelength of Yb-based fiber lasers. The incorporation of an α,β′-pyridine moiety into expanded porphyrins opens a highly interesting area of research due to the attractive optical and coordination properties of the resulting molecules.     

Loading of Amino Acids onto RNA in a Putative RNA-Peptide World

RNA is a molecule that can both store genetic information and perform catalytic reactions. This observed dualism places RNA into the limelight of concepts about the origin of life. The RNA world concept argues that life started from self-replicating RNA molecules, which evolved toward increasingly complex structures. Recently, we demonstrated that RNA, with the help of conserved non-canonical nucleosides, which are also putative relics of an early RNA world, had the ability to grow peptides covalently connected to RNA nucleobases, creating RNA-peptide chimeras. It is conceivable that such molecules, which combined the information-coding properties of RNA with the catalytic potential of amino acid side chains, were once the structures from which life emerged. Herein, we report prebiotic chemistry that enabled the loading of both nucleosides and RNAs with amino acids as the first step toward RNA-based peptide synthesis in a putative RNA-peptide world.