An application of UV-derivative spectrophotometry and bivariate calibration algorithm for study of photostability of levomepromazine hydrochloride

Derivative spectrophotometry and bivariate calibration algorithm were used for study of run of photooxidation of levomepromazine hydrochloride (LV). The actual concentrations of LV and its main degradation product levomepromazine sulphoxide (LV-SO) were calculated using data provided by applied methods. The direct reading of absorbance values at 302 nm and 334 nm were employed for quantification of LV and LV-SO, respectively, in the case of bivariate method. The derivative spectrophotometric method is based on transformation of zero-order spectra into first derivative. The values of first derivative at 334 nm were used for quantification of LV while at 278 nm for assay of LV-SO. The obtained quantitative data were applied for investigation of kinetics of photodegradation of LV.     

Investigation of solvolysis kinetics of new synthesized fluocinolone acetonide C-21 esters--an in vitro model for prodrug activation

In this study the solvolysis of newly synthesized fluocinolone acetonide C-21 esters was analysed in comparison with fluocinonide during a 24-hour period of time. The solvolysis was performed in an ethanol-water (90:10 v/v) mixture using the excess of NaHCO?. The solvolytic mixtures of each investigated ester have been assayed by a RP-HPLC method using isocratic elution with methanol-water (75:25 v/v); flow rate 1 mL/min; detection at 238 nm; temperature 25 °C. Solvolytic rate constants were calculated from the obtained data. Geometry optimizations and charges calculations were carried out by Gaussian W03 software. A good correlation (R = 0.9924) was obtained between solvolytic rate constants and the polarity of the C-O2 bond of those esters. The established relation between solvolytic rate constant (K) and lipophilicity (cLogP) with experimental anti-inflammatory activity could be indicative for topical corticosteroid prodrug activation.     

A novel application of Onyx™ monolithic column for simultaneous determination of salicylic acid and triamcinolone acetonide by sequential injection chromatography

A novel and fast simultaneous determination of triamcinolone acetonide (TCA) and salicylic acid (SA) in topical pharmaceutical formulations by sequential injection chromatography (SIC) as an alternative to classical high performance liquid chromatography (HPLC) has been developed. A recently introduced Onyx™ monolithic C18 (50 mm × 4.6 mm, Phenomenex^®) with 5 mm monolithic precolumn were used for the first time for creating sequential injection chromatography system based on a FIAlab^® 3000 with a six-port selection valve and 5.0 mL syringe pump in study. The mobile phase used was acetonitrile/water (35:65, v/v), pH 3.3 adjusted with acetic acid at flow rate 0.9 mL min⁻¹. UV detection provided by fibre-optic DAD detector was set up at 240 nm. Propylparaben was chosen as suitable internal standard (IS). There is only simple pre-adjustment of the sample of topical solution (dilution with mobile phase) so the analysis is not uselessly elongated. Parameters of the method showed good linearity in wide range, correlation coefficient >0.999; system precision (relative standard deviation, R.S.D.) in the range 0.45-1.95% at three different concentration levels, detection limits (3σ) 1.00 μg mL⁻¹ (salicylic acid), 0.66 μg mL⁻¹ (triamcinolone acetonide) and 0.33 μg mL⁻¹ (propylparaben) and recovery from the pharmaceutical preparations in the range 97.50-98.94%. The chromatographic resolution between peaks of compounds was more than 4.5 and analysis time was 5.1 min under the optimal conditions. The advantages of sequential injection chromatography against classical HPLC are discussed and showing that SIC can be a method of option in many cases.     

荧光光谱法测定氨基酸的新方法

在醋酸 醋酸钠缓冲介质中 ,氨基酸能猝灭壳聚糖 茚三酮体系的荧光。基于此 ,建立了一种新的荧光光谱测定氨基酸的方法 ,探讨了其反应机理及测定条件。方法的线性范围为 0mol·L- 1 ～ 1 2× 1 0 - 4 mol·L- 1 ,已应用于测定果汁饮料     

Synthesis and molecular structure of a novel barium arylspiroboronate ester

The compound barium bis{bis-(4,6-di-tert-butyl[1,2-benzenediolato(2-)-O,O′]borate)} has been prepared by the addition of 3,5-di-tert-butylcatechol to a solution of boric acid and Ba(OH)₂ and characterized by a single crystal X-ray diffraction study. The title compound crystallized in the triclinic space group P-1, with cell parameters a = 13.280(2) Å, b = 15.755(3) Å, and c = 16.980(3) Å, α = 71.691(2)o, β = 79.528(3)o, γ = 80.741(3)o, Z = 1, and V = 3296.1(10) ų. The structure was solved by direct methods and refined to a final R = 0.0459 for 14370 reflections with I > 2σ(I). One of the arylspiroboronate ester counterions is bound to the barium atom in a rare example of the η1 bonding mode via a single oxygen of one of the catecholato groups. The coordination sphere around the barium is complemented by four molecules of water, one molecule of acetone and two bridging water molecules, connecting to an adjacent barium atom.     

Aroylethenesulfonylacetic acid methyl ester: a synthon for novel sulfone linked bis heterocycles

Novel sulfone linked bis heterocycles containing two different heterocyclic rings viz., pyrazoline in combination with thiadiazole, oxadiazole and triazole were synthesized and studied their antimicrobial activity.     

An application of second-order n-electron valence state perturbation theory to the calculation of excited states

n–electron valence state perturbation theory (NEVPT) is a form of multireference perturbation theory where all the zero-order wave functions are of multireference nature, being generated as eigenfunctions of a two–electron model Hamiltonian. The absence of intruder states makes NEVPT an interesting choice for the calculation of electronically excited states. Test calculations have been performed on several valence and Rydberg transitions for the formaldehyde and acetone molecules; the results are in good accordance with the best calculations and with the existing experimental data.Contribution to the Jacopo Tomasi Honorary Issue     

Combined use of algorithms for peak picking, peak tracking and retention modelling to optimize the chromatographic conditions for liquid chromatography-mass spectrometry analysis of fluocinolone acetonide and its degradation products

A strategy for rapid optimization of liquid chromatography column temperature and gradient shape is presented. The optimization as such is based on the well established retention and peak width models implemented in software like e.g. DryLab and LC simulator. The novel part of the strategy is a highly automated processing algorithm for detection and tracking of chromatographic peaks in noisy liquid chromatography-mass spectrometry (LC-MS) data. The strategy is presented and visualized by the optimization of the separation of two degradants present in ultraviolet (UV) exposed fluocinolone acetonide. It should be stressed, however, that it can be utilized for LC-MS analysis of any sample and application where several runs are conducted on the same sample. In the application presented, 30 components that were difficult or impossible to detect in the UV data could be automatically detected and tracked in the MS data by using the proposed strategy. The number of correctly tracked components was above 95%. Using the parameters from the reconstructed data sets to the model gave good agreement between predicted and observed retention times at optimal conditions. The area of the smallest tracked component was estimated to 0.08% compared to the main component, a level relevant for the characterization of impurities in the pharmaceutical industry.     

Synthesis and thermal decomposition of a novel hyperbranched polyphosphate ester used for flame retardant systems

A novel hyperbranched polyphosphate ester (HPPE) was synthesized via the polycondensation of bisphenol-A as an A₂ monomer and phosphoryl trichloride as a B₃ monomer at 100 °C, without gelation. The initial molar ratio of A₂ to B₃ was set to be 1.5:1. The final product was precipitated from methanol. ³¹P NMR spectroscopy was used to monitor the reaction. The formed HPPE was characterized by FTIR and ¹H NMR to confirm its end groups. Differential scanning calorimetry data revealed that the cured bisphenol-A epoxy resin with HPPE as a curing agent possessed improved glass transition temperature. Dynamic mechanical thermal analysis also showed the increase in the glass transition temperature. The thermal degradation properties and flame retardancy were investigated by thermogravimetric analysis and limiting oxygen index (LOI). The results showed that the incorporation of HPPE into bisphenol-A epoxy resin increased its thermal stability and char yield during the decomposition by raising the second stage decomposition temperature. The LOI value increased from 23 to 31 when HPPE, instead of bisphenol-A, was used as a curing agent.     

An LC–MS/MS method for quantification of demethylzeylasteral,a novel immunosuppressive agent in rat plasma and the application to a pharmacokinetic study

In this study, a sensitive liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed and validated for the quantification of demethylzeylasteral in rat plasma. Electrospray ionization was operated in the negative ion mode while demethylzeylasteral and oleanolic acid (internal standard) were measured by selected reaction monitoring (demethylzeylasteral: m/z 479.2 → 436.0; oleanolic acid: m/z 454.9 → 407.2). This LC–MS/MS method had good selectivity, sensitivity, accuracy and precision. The pharmacokinetic profiles of demethylzeylasteral were subsequently examined in Wistar rats after oral or intravenous administration.     

An ESR and NMR study of the gamma radiolysis of a bisphenol-A based polycarbonate and a phthalic acid ester

A study of the γ-radiolysis of the commercial polymers U-polymer, UP (Unitake) and polycarbonate, PC, (Aldrich) has been undertaken using ESR spectroscopy. The G-value of radical formation at 77 K has been found to be 0.31±0.01 for UP and 0.5±0.02 for PC. By using thermal annealing and spectral subtraction, the paramagnetic species formed on irradiation has been assigned. The effect of radiation on the chemical structure of UP and PC has been investigated at ambient temperature and at 423 K. The NMR results show that a new phenol type chain end is formed in the polymers on exposure to γ-radiation. The G-value of formation of the new phenol ends was estimated to be 0.7 for PC (423 K) and 0.4 for UP (300 K). © 1998 John Wiley & Sons, Ltd.     

Synthesis of novel quinone boronic ester derivatives via a highly regioselective Cr-mediated benzannulation reaction and their application in Pd-catalyzed coupling processes

This paper describes the synthesis and reactivity of a novel class of quinone boronic esters. These compounds are prepared utilizing a highly regioselective D?tz annulation of Fischer carbene complexes with alkynylboronates. All substrates studied to date provided a single regioisomeric arylboronic ester product; the origin of this selectivity is discussed in the context of steric and electronic effects. Additionally, these compounds have been found to undergo Pd-catalyzed coupling reactions with a range of aryl and allyl halides and provides a strategy for the selective and predictable preparation of highly substituted quinones and hydroquinones. Finally, the propensity of this technique to prepare highly functionalized aromatic compounds in an expeditious fashion is demonstrated in the total synthesis of dimeric carbazole (+/-)-bis-N-dimethylbismurrayaquinone-A 33.     

Efficient two directional syntheses of a homophthalate ester and novel resorcylate oligomers

Thermolysis of 6,6′-(2-oxopropane-1,3-diyl)bis(2,2-dimethyl-4H-1,3-dioxin-4-one) in the presence of methanol gave a triketo-ester which subsequently aromatized to provide a synthetically useful homophthalate ester. Enolate C-acylation in the presence of diethylzinc was used to synthesize other double diketo-dioxinones, which on cyclization, aromatization and dioxinone ring opening gave novel double resorcylate derivatives.     

Synthesis of a novel betaine-type asphalt emulsifier and its investigation by online FTIR spectrophotometry

A novel betaine-type asphalt emulsifier, 3-(dodecyloxy)-2-hydroxypropan-N-carboxymethyl-N,N-dimethylammonium chloride, has been synthesized in a three-step reaction from lauryl alcohol, epichlorohydrin, dimethylamine, and chloroacetic acid. The optimum reaction conditions were obtained for synthesis of 2-(dodecyloxymethyl)oxirane in the first step. The yield reaches 75.7 % under the optimum conditions of reaction temperature 50 °C, reaction time 5 h, feedstock mole ratio of epichlorohydrin to lauryl alcohol 1.4, basicity 33.3 %. The structures of the three products were identified by FTIR. Synthesis of 2-(dodecyloxymethyl)oxirane in the first step was monitored by online FTIR, and an intermediate was detected. On the basis of the experimental data, a plausible reaction mechanism was proposed for the reaction. The critical micelle concentration (CMC) of the final product is low, 8.8 × 10^?5 mol/L. The surface tension at the CMC is 21.2 mN/m. This product is an excellent emulsifier for asphalt. The prepared bituminous emulsion had high storage stability. The emulsifier is a rapid-set asphalt emulsifier.     

Theory of second-order Raman scattering from a zigzag chain with application to polyethylene

The extinction coefficient for acoustic branch, second-order (two-phonon) Raman scattering from a zigzag chain, using force constants and polarizabilities appropriate to polyethylene is computed. As a consequence of the computation, we propose identification of a line at 890 cm^?1 in the published Raman spectrum of polyethylene as a second-order Raman line.