Use of non-aqueous capillary electrophoresis for the quality control of commercial saffron samples

A non-aqueous capillary electrophoresis (NACE) method for quantifying the seven crocin metabolites that are the major biologically active ingredients of saffron was developed. Separation is done by using a fused silica capillary filled with a 12.5 mM H3BO3/37.5 mM sodium tetraborate methanolic solution as background electrolyte. The results obtained were compared with the total index "safranal value", widely used as a quality measure of saffron products. The comparison revealed that the proposed NACE method provides useful information not obtained in the safranal value. Infact, samples with a similar safranal value can contain crocin metabolites in different concentrations and relative proportions. This new method is very useful for quality control in commercial saffron samples.     

Practical and quality-control aspects of multi-element analysis with quadrupole ICP–MS with special attention to urine and whole blood

Two screening methods were developed for rapid analysis of a great number of urine and blood samples within the framework of an exposure check of the population after a firework explosion. A total of 56 elements was measured including major elements. Sample preparation consisted of simple dilution. Extensive quality controls were applied including element addition and the use of certified reference materials. Relevant results at levels similar to those found in the literature were obtained for Co, Ni, Cu, Zn, Sr, Cd, Sn, Sb, Ba, Tl, and Pb in urine and for the same elements except Ni, Sn, Sb, and Ba in blood. However, quadrupole ICP–MS has limitations, mainly related to spectral interferences, for the analysis of urine and blood, and these cause higher detection limits. The general aspects discussed in the paper give it wider applicability than just for analysis of blood and urine—it can for example be used in environmental analysis.     

Decomposition of Toluene and Acetone in Packed Dielectric Barrier Discharge Reactors

The influences of TiO₂ catalytic material and glass pellet packing on the decomposition efficiency of toluene and acetone in air by dielectric barrier discharge (DBD) reactors were experimentally investigated in this study. The effects of both packing materials on the formation of byproducts such as CO and CO₂ were also evaluated. Experimental results indicate that the introduction of glass materials into the plasma zone of a wire-tube reactor would improve the decomposition efficiency of toluene and acetone compared to a nonpacked reactor. The apparent decomposition rate constant of a glass packed-bed reactor was 4.5–4.8 times greater than that of a nonpacked reactor. The results also indicate that the decomposition rate constant of toluene was approximately 2.6 times higher than that of acetone no matter which type reactor was utilized. The application of TiO₂ coated pellets in DBD reactors will enforce the hydrocarbon byproducts to further be oxidized to CO₂, notwithstanding, it will not significantly improve the performance of the reactors in the decomposition of toluene and acetone, and in the formation of CO. The results show that the best selectivity of CO₂ for acetone decomposition in a TiO₂ coated pellets packed-bed reactor was approximately 40% higher than that in a glass packed-bed reactor.     

Preparation of VPS and PVD coatings for metallographic and TEM investigations

The aim of the first part of the paper is to give some advice for the faultless metallographic preparation of vacuum plasma sprayed coatings. Several coating/substrate combinations using metals, alloys and ceramics were investigated to derive some general rules. The second part deals with a preparation technique for cross-sections- of physical vapour deposition coatings. This technique was optimized for TiN and Ti(C, N) coatings on hardmetals which were examined in an analytical transmission electron microscope.     

Development and Validation of a High Performance Liquid Chromatographic Method for the Determination of Voriconazole Content in Tablets

This paper describes the validation of an isocratic HPLC method for the assay of voriconazole in tablets. The method employs a Merck LiChrospher^? 100 RP-8 (125 × 4.6 mm I.D., 5 μm particle size) column, with a mobile phase of methanol : triethylamine solutions 0.6 %, pH 6.0 (50:50, v/v) and UV detection at 255 nm. A linear response (r > 0.9999) was observed in the range of 20.0–100.0 μg mL⁻¹. The method showed good recoveries (average 100.4%) and the relative standard deviation intra and inter-day were ≤ 1.0 %. Validation parameters as specificity and robustness were also determined. The method can be used for both quality control assay of voriconazole in tablets and for stability studies as the method separates voriconazole from its degradation products and tablet excipients.     

Optimizing control of simulated moving beds--linear isotherm

A new optimization based adaptive control strategy for simulated moving beds (SMBs) is proposed. A linearized reduced order model, which accounts for the periodic nature of the SMB process, is used for online optimization and control. The manipulated variables are the four inlet flow rates, the outputs are the raffinate and extract concentrations. Concentration measurements at the raffinate and extract outlets are used as the feedback information. The state estimate from the periodic Kalman filter is used for the prediction of the outlet concentrations over a chosen horizon. Predicted outlet concentrations are the basis for the calculation of the optimal input adjustments, which maximize the productivity and minimize the desorbent consumption subject to constraints on product purities. The realization of this concept is discussed and the implementation on a virtual eight column SMB platform is assessed, in the case of binary linear systems. For a whole series of typical plant disturbances it is shown that the proposed approach is effective in minimizing off-spec products and in achieving optimal SMB operation, also in the case where there are significant model uncertainties.     

Value function and optimality conditions for semilinear control problems

This paper is concerned with optimal control problems of Mayer and Bolza type for systems governed by a semilinear state equationx(t)=Ax(t) + f(t, x(t), u(t)), u(t) U, whereA is the infinitesimal generator of a strongly continuous semigroup in a Banach spaceX. We prove necessary and sufficient conditions for optimality and then use these conditions to investigate properties of the value function related to superdifferentials. Conversely, we use the value function to obtain criteria for optimality and feedback systems.Work (partially) supported by the Research Project Equazioni di evoluzione e applicazioni fisicomatematiche (M.U.R.S.T.-Italy).     

Necessary and sufficient conditions for the existence of positive solutions to algebraic Riccati equations with indefinite quadratic term

Necessary and sufficient conditions are established in this paper for the existence of positive- and/or negative-definite solutions to the algebraic Riccati equation with indefinite coefficient. An iterative procedure is also given for computing such a solution.Project supported by the National Science Foundation of China and by the special program of the State Education Commission of China under grant 9033507.