Rapid optimized separation of bromide in serum samples with capillary zone electrophoresis by using glycerol as additive to the background electrolyte

After decades of neglect, bromide has recently been re-introduced in therapy as an effective anti-epileptic drug. The present paper describes the methodological optimization and validation of a method based on capillary zone electrophoresis for the rapid determination of bromide in serum using a high-viscosity buffer and a short capillary (10 cm). The optimized running buffer was composed of 90 mM sodium tetraborate, 10 mM sodium chloride, pH 9.24 and 25% glycerol. The separation was carried out at 25 kV at a temperature of 20 °C. Detection was by direct UV absorption at 200 nm wavelength. The limit of detection (signal-to-noise ratio = 5) in serum was 0.017 mM. The precision of the method was verified in blank serum samples spiked with bromide, obtaining intra-day and day-to-day tests, relative standard deviation values ≤0.2% in terms of migration times and values <2% in terms of peaks areas, respectively.     

Multielement (H,C, N,O, S) stable isotope characteristics of lamb meat from different Italian regions

The study focuses on the ²H/H, ¹³C/¹²C, ¹⁵N/¹⁴N, ¹⁸O/¹⁶O and ³⁴S/³²S values of defatted dry matter (DFDM) and on the ²H/H, ¹³C/¹²C and ¹⁸O/¹⁶O values of the fat fraction of meat samples from various lamb types reared in seven Italian regions, following different feeding regimes (forage, concentrate, milk). The ¹³C/¹²C (r = 0.922), ²H/H (r = 0.577) and ¹⁸O/¹⁶O (r = 0.449) values of fat and DFDM are significantly correlated, the fat values being significantly lower for C and H and higher for O than for DFDM values and the differences between the two fractions not being constant for different lamb types. The feeding regime significantly affected the ¹³C/¹²C, ¹⁵N/¹⁴N, ¹⁸O/¹⁶O and ²H/H of fat. The DFDM ²H/H, and ¹⁸O/¹⁶O values, excluding an outlier, are significantly correlated with the corresponding values in meteoric waters, thus allowing us to trace the variability of geoclimatic factors. ¹⁵N/¹⁴N is influenced by pedoclimatic conditions, whereas ³⁴S/³²S is influenced by the sea spray effect and the surface geology of the provenance area. By applying stepwise linear discriminant analysis only the ²H/H of fat was found not to be significant and 97.7% of the samples were correctly assigned to the lamb type and more than 90% cross‐validated. With the feeding regime, 97.7% of the samples were both correctly assigned and cross‐validated using a predictive model including ¹³C/¹²C, ¹⁵N/¹⁴N, ¹⁸O/¹⁶O, ³⁴S/³²S of DFDM and ¹⁸O/¹⁶O of fat. Copyright © 2009 John Wiley & Sons, Ltd.     

Comparing different metaheuristic approaches for the median path problem with bounded length

In this paper we consider the Bounded Length Median Path Problem which can be defined as the problem of locating a path-shaped facility that departures from a given origin and arrives at a given destination in a network. The length of the path is assumed to be bounded by a given maximum length. At each vertex of the network (customer-point) the demand for the service is given and the cost to reach the closest service-point is computed. The objective is to minimize the sum of these costs over all the customer-points in the network.     

Development and validation of a gas chromatography/mass spectrometry method for the assessment of genomic DNA methylation

A method for the determination of DNA global methylation, taken as the ratio (%) of 5‐methylcytosine (5mCyt) versus the sum of cytosine (Cyt) and 5mCyt, via gas chromatography/mass spectrometry (GC/MS), was developed and validated. DNA (2.5 µg) was hydrolyzed with aqueous formic acid 88%, spiked with cytosine‐2,4‐¹³C₂,¹⁵N₃ and 5‐methyl‐²H₃‐cytosine‐6‐²H₁ as internal standards, and derivatized with N‐methyl‐N‐(tert‐butyldimethylsilyl)trifluoroacetamide and 1% tert‐butyldimethylchlorosilane, in the presence of acetonitrile and pyridine. GC/MS, operating in single ion monitoring mode, separated and specifically detected all nucleobases as tert‐butyldimethylsilyl derivatives, without interferences, with the exception of guanosine. The method was linear throughout the range of clinical interest and had good sensitivity, with a limit of quantification of 3.2 pmol for Cyt and 0.056 pmol for 5mCyt, the latter corresponding to a methylation level of 0.41%. Intra‐ and inter‐day precision and accuracy were below 4.0% for both analytes and methylation. The matrix absolute effect, process efficiency and coefficient of variation ranged from 96.5 to 101.2%. The matrix relative effect was below 1%. The method was applied to the analysis of different human DNAs, including: nonmethylated DNA from PCR (methylation 0.00%), hypermethylated DNA prepared using M.SssI CpG methyltransferase (methylation 18.05%), DNA from peripheral blood leukocytes of healthy subjects (N = 6, median methylation 5.45%), DNA from bone marrow of leukemia patients (N = 5, 3.58%) and DNA from myeloma cell lines (N = 4, 2.74%). Copyright © 2009 John Wiley & Sons, Ltd.     

Enantiopure N-Boc piperidine-2-ethanol for the synthesis of (+)- and (−)-dumetorine,and (+)- and (−)-epidihydropinidine

The convenient synthesis of both enantiomers of the piperidine alkaloids such as dumetorine and epidihydropinidine is described. Pure enantiomers of 2-(2-hydroxy-ethyl)-piperidine-1-carboxylic acid tert-butyl ester are used as a common starting material. The syntheses are based on a RCM reaction and on methylation of the piperidine ring according to Beak–Lee methodology, respectively.     

Spherical polymer brushes under good solvent conditions: molecular dynamics results compared to density functional theory

A coarse grained model for flexible polymers end-grafted to repulsive spherical nanoparticles is studied for various chain lengths and grafting densities under good solvent conditions by molecular dynamics methods and density functional theory. With increasing chain length, the monomer density profile exhibits a crossover to the star polymer limit. The distribution of polymer ends and the linear dimensions of individual polymer chains are obtained, while the inhomogeneous stretching of the chains is characterized by the local persistence lengths. The results on the structure factor of both single chain and full spherical brush as well as the range of applicability of the different theoretical tools are presented. Finally, a brief discussion of the experiment is given.     

Fluoroquinolone antibiotics in environmental waters: Sample preparation and determination

The aim of this review is to provide a general overview on the analytical methods proposed in the last decade for trace fluoroquinolone (FQ) determination in environmental waters. A large number of studies have been developed on this topic in reason of the importance of their monitoring in the studies of environmental mobility and potential degradation pathways. Every step of the analysis has been carefully considered, with a particular attention to sample preparation, in relationship with the problems involved in the analysis of real matrices. The different strategies to minimise interference from organic matter and to achieve optimal sensitivity, especially important in those samples with lower FQ concentrations, were also highlighted. Results and progress in this field have been described and critically commented. Moreover, a worldwide overview on the presence of FQs in the environmental waters has been reported.     

Study on the racemization of synephrine by off-column chiral high-performance liquid chromatography

In this study, the racemization kinetic parameters of R-(−)-synephrine, the active phenethylamine alkaloid of Citrus aurantium L., were determined by means of an off-column HPLC method. Enantioseparation was carried out in different buffer solutions and solvents on a chiral stationary phase (CSP) with cellobiohydrolase as the chiral selector (Chiral-CBH, 100 mm × 4.0 mm i.d., 5 μm). The mobile phase was 10 mM sodium phosphate buffer (pH 6.0)-2-propanol (95:5, w/w), with 50 μM disodium EDTA, at 0.8 mL/min. The column was thermostatted at 20 °C and detection was set at 225 nm. The influence of pH value, ionic strength, temperature and addition of organic modifier on the rate constant, the half-life of racemization and the free energy barrier of racemization of R-(−)-synephrine were determined. Among the different chemical and physical parameters evaluated as affecting the racemization of naturally occurring R-(−)-synephrine, pH, temperature and addition of an organic co-solvent appear to have the strongest effect, while ionic strength does not exert a significant influence on the racemization rate. The results of the present study indicated that synephrine racemization is possible at high temperature at both acidic and basic pH values; therefore, the extraction procedure of R-(−)-synephrine from the plant material should be carried out under specific conditions to preserve the stereochemical integrity and the biological activity of this secondary metabolite.     

HJB equations in infinite dimensions with locally Lipschitz Hamiltonian and unbounded terminal condition

We study Hamilton Jacobi Bellman equations in an infinite dimensional Hilbert space, with Lipschitz coefficients, where the Hamiltonian has superquadratic growth with respect to the derivative of the value function, and the final condition is not bounded. This allows to study stochastic optimal control problems for suitable controlled state equations with unbounded control processes. The results are applied to a controlled wave equation.