Optimization of gas chromatographic-mass spectrometric analysis for fatty acids in hydrogenated castor oil obtained by catalytic transfer hydrogenation

Optimization of the analytical conditions for determination of the partially hydrogenated products of castor oil obtained by catalytic hydrogen transfer, using Pd/C, with limonene as hydrogen source, was carried out in this work. The study involved the use of three capillary columns: SPB-1, HP-5 and HP-20 M. The best resolution for the oleic acids isomers, C18:1, was obtained with HP-20 M column while, the best resolution, identification and quantification for the products containing OH and CO were obtained with a HP-5 column after the silylation of the methyl esters.     

Development of a Molecularly Imprinted Poly(Acrylic Acid)‐MWCNT Nanocomposite Electrochemical Sensor for Tramadol Determination in Pharmaceutical Samples

A new voltammetric sensor based on molecularly imprinted poly(acrylic acid)‐MWCNT nanocomposite (MIP‐MWCNT) drop‐coated onto glassy carbon electrode (GCE) was developed and applied to tramadol (TR) determination in pharmaceutical samples. The voltammetric sensor prepared by suspension of MIP‐MWCNT at 1 : 1 (w/w) ratio show an improved performance compared to unmodified GCE. The electrochemical method is based on preconcentration of tramadol onto MIP‐MWCNT modified GCE surface at ?1.5 V vs Ag/AgCl for 180 s in 0.1 Britton‐Robinson buffer (pH 8.0) at stirred solution. Upon preconcentration, the differential anodic voltammogram was recorded under the optimized condition giving rise to an analytical curve varying from 9.0 up to 30.0 μmol L^?1 (R²=0.997) and limits of detection and quantification of 1.4 and 4.8 μmol L^?1, respectively. The method precision was assessed in terms of intraday (n=6) and interday (two consecutive days) precision, giving relative standard deviations (RSD%) values between 2.8 to 7.4 %. Excipients usually found in pharmaceutical pills (magnesium stearate, microcrystalline cellulose, starch, and silica) and paracetamol were evaluated as potential interferents, however no interference was evidenced in TR determination. The method applicability was evaluated by TR analysis in pharmaceutical samples. Moreover, the method accuracy was attested by comparison of addition and recovery assays with a reference technique (high‐performance liquid chromatography).     

Temperature-dependent facet development in the deposition of GaInP on non-planar surfaces

The low-pressure (20 mbar) organometallic vapour-phase epitaxy (LP-OMVPE) of GaInP on non-planar {001} GaAs substrates has been examined. The encountered and {1 0} faceting features develop along the bottom corner and the top edge configurations of the inverted and dovetail grooves, respectively. At higher temperatures (T ≥ 720°C) these features are no longer present. The results have been compared to computer simulations of surface concentration profiles, whereby the inversely proportional relation between temperature and supersaturation, along with varying growth rate on adjacent surfaces of different crystallographic orientations, is found to be the driving force behind the occurrence of these features. The stability of the observed facets is related to the decrease in dangling-bond densities upon surface reconstruction.     

Simultaneous quantitation of nicorandil and its denitrated metabolite in plasma by LC-MS/MS: application for a pharmacokinetic study

A liquid chromatography-electrospray ionization tandem mass spectrometry method was developed and validated for the simultaneous quantitation of nicorandil and its denitrated metabolite, N-(2-hydroxyethyl)-nicotinamide, in rat plasma. After a liquid-liquid extraction step, chromatographic separation was performed on a ShinPack C(18) column with an isocratic mobile phase composed of methanol and 2 mM aqueous ammonium acetate containing 0.03% (v/v) formic acid (33:67 v/v). Procainamide was used as an internal standard (IS). Selected reaction monitoring was performed using the transitions m/z 212 → m/z 135, m/z 166 → m/z 106 and m/z 236 → m/z 163 to quantify nicorandil, its denitrated metabolite and IS, respectively. Calibration curves were constructed over the range of 5-15,000 ng.ml(-1) for both nicorandil and its metabolite. The mean relative standard deviation (RSD%) values for the intra-run precision were 5.4% and 7.3% and for the inter-run precision were 8.5% and 7.3% for nicorandil and its metabolite, respectively. The mean accuracy values were 100% and 95% for nicorandil and its metabolite, respectively. No matrix effect was detected in the samples. The validated method was successfully applied to a pharmacokinetic study after per os administration of nicorandil in rats.     

Antimicrobial evaluation of diterpenes from Copaifera langsdorffii oleoresin against periodontal anaerobic bacteria

The antimicrobial activity of four labdane-type diterpenes isolated from the oleoresin of Copaifera langsdorffii as well as of two commercially available diterpenes (sclareol and manool) was investigated against a representative panel of microorganisms responsible for periodontitis. Among all the evaluated compounds, (-)-copalic acid (CA) was the most active, displaying a very promising MIC value (3.1 μg mL-1; 10.2 μM) against the key pathogen (Porphyromonas gingivalis) involved in this infectious disease. Moreover, CA did not exhibit cytotoxicity when tested in human fibroblasts. Time-kill curve assays performed with CA against P. gingivalis revealed that this compound only inhibited the growth of the inoculums in the first 12 h (bacteriostatic effect). However, its bactericidal effect was clearly noted thereafter (between 12 and 24 h). It was also possible to verify an additive effect when CA and chlorhexidine dihydrochloride (CHD, positive control) were associated at their MBC values. The time curve profile resulting from this combination showed that this association needed only six hours for the bactericidal effect to be noted. In summary, CA has shown to be an important metabolite for the control of periodontal diseases. Moreover, the use of standardized extracts based on copaiba oleoresin with high CA contents can be an important strategy in the development of novel oral care products.     

Constructive factorization of some almost periodic triangular matrix functions with a quadrinomial off diagonal entry

Using an abbreviation eμ to denote the function eiμx on the real line R, let , where f is a linear combination of the functions eα, eβ, eα−λ, eβ−λ with some . The criterion for G to admit a canonical factorization was established recently by Avdonin, Bulanova and Moran (2007) [1]. We give an alternative approach to the matter, proving the existence (when it does take place) via deriving explicit factorization formulas. The non-existence of the canonical factorization in the remaining cases then follows from the continuity property of the geometric mean.     

Evaluation of laser induced breakdown spectroscopy for multielemental determination in soils under sewage sludge application

Laser induced breakdown spectroscopy (LIBS) is an atomic emission spectroscopy technique for simple, direct and clean analysis, with great application potential in environmental sustainability studies. In a single LIBS spectrum it is possible to obtain qualitative information on the sample composition. However, quantitative analysis requires a reliable model for analytical calibration. Multilayer perceptron (MLP), an artificial neural network, is a multivariate technique that is capable of learning to recognize features from examples. Therefore MLP can be used as a calibration model for analytical determinations. Accordingly, the present study proposes to evaluate the traditional linear fit and MLP models for LIBS calibration, in order to attain a quantitative multielemental method for contaminant determination in soil under sewage sludge application. Two sets of samples, both composed of two kinds of soils were used for calibration and validation, respectively. The analyte concentrations in these samples, used as reference, were determined by a reference analytical method using inductively coupled plasma optical emission spectrometry (ICP OES). The LIBS-MLP was compared to a LIBS-linear fit method. The values determined by LIBS-MLP showed lower prediction errors, correlation above 98% with values determined by ICP OES, higher accuracy and precision, lower limits of detection and great application potential in the analysis of different kinds of soils.     

Non-Abelian tensor square and related constructions of p-groups

Archiv der Mathematik - Let G be a group. We denote by $$\nu (G)$$ a certain extension of the non-Abelian tensor square $$[G,G^{\varphi }]$$ by $$G \times G$$. We prove that if G is a finite potent...