Electrospray ion-trap multistage mass spectrometry for characterisation of co-monomer compositional distribution of bacterial poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) at the molecular level

We report an electrospray ionisation multistage mass spectrometry (ESI-MSn) method that utilises molecular mass information for determination of sequence distribution and chemical structure of mass-selected macromolecules of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) biopolyester, PHBH. On the basis of ESI-MSn studies of PHBH oligomers obtained by partial alkaline depolymerisation of natural PHBH containing 13-14 mol% of hydroxyhexanoate (HH) units, the microstructure of this bacterial copolyester was assessed up to the level of 28 repeat units. The subtle structural details of the PHBH were evaluated based on sequencing of individual macromolecular ions thus showing the utility of this technique for the analysis of biological copolyester macromolecules. It was confirmed that both HH and hydroxybutyrate (HB) units of the PHBH copolymer are randomly distributed.     

Videodensitometric HPTLC Determination of Fleroxacin,Sparfloxacin, and Cinoxacin in Tablets

JPC – Journal of Planar Chromatography – Modern TLC - A new, simple, accurate, and rapid high-performance thin-layer chromatographic method has been developed for the determination of...     

Designing of dipeptide‐based oligoconjugates as potential carrier for drug delivery. Pyroglutamil‐S‐glutamic acid bisoligo‐3‐hydroxybutyrates

In the present article, we describe the synthesis and characterization of conjugates based on pyroglutamyl‐S‐glutamic acid and bisoligo‐[R,S]‐3‐hydroxybutyrates (PyGlu‐S_‐Glu_bisOHB) using anionic ring opening polymerization of β‐butyrolactone with a dipeptide bearing two carboxylate groups as potassium salt. The results indicated that the above‐mentioned reaction is accompanied of oligomerization of β‐butyrolactone yielding (3‐hydroxybutyrates) oligomers with crotonate and carboxyl end groups. We report also the end group analysis of the synthesized conjugates using electrospray ionization tandem mass spectrometry (ESI‐MS), the latter confirmed the presence of a mixture of dipeptide conjugate with β‐butyrolactone oligomer chain and β‐butyrolactone homopolymer. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4103–4111, 2008     

Disperse red 1 end capped oligoesters. Synthesis by noncatalyzed ring opening oligomerization and structural characterization

The synthesis of novel azofunctional oligoesters through bulk ring opening of ε‐caprolactone and D ,L ‐lactide (LA) at 100 and 130 °C, respectively, mediated by N‐ethyl‐N‐(2‐hydroxyethyl)‐4‐(4‐nitrophenylazo)aniline (Disperse Red 1) (DR1) is described. The synthetic procedure allows “clean” products because no catalysts were used in the reaction. Moreover, DR1 moiety is showed for the first time to promote the ring opening of cyclic esters. The molecular structure of the obtained oligoesters was established by NMR spectroscopy, MALDI ToF MS and electrospray ionization mass spectrometry (ESI MS). ESI‐MS/MS fragmentation experiments were used to demonstrate the nature of the chain end groups (hydroxyl and DR1). Intermolecular transesterification reactions were proved by mass spectrometry studies at least in the case of LA oligomerization. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 534–547, 2009     

RP-TLC Separation of Antiarrhythmic Drugs. Densitometric Analysis of Flecainide in Tablets

JPC – Journal of Planar Chromatography – Modern TLC - The chromatographic behavior of some antiarrhythmic compounds has been studied on commercially available TLC plates coated with...     

Nonlinear vibrations and time delay control of an extensible slowly rotating beam

Nonlinear Dynamics - This paper investigates the time-varying formation tracking (TVFT) problem of multiple heterogeneous Euler–Lagrange agents (MHELAs) with predefined-time convergence...     

The influence of chemical structure on thermal properties and surface morphology of polyurethane materials

The surface morphology and thermal properties of polyurethanes can be correlated to their chemical composition. The hydrophilicity, surface morphology, and thermal properties of polyurethanes (differed in soft segments and in linear/cross-linked structure) were investigated. The influence of poly([R,S]-3-hydroxybutyrate) presence in soft segments and blending of polyurethane with polylactide on surface topography were also estimated. The linear polyurethanes (partially crystalline) had the granular surface, whereas the surface of cross-linked polyurethanes (almost amorphous) was smooth. Round aggregates of polylactide un-uniformly distributed in matrix of polyurethane were clearly visible. It was concluded that some modification of soft segment (by mixing of poly([R,S]-3-hydroxybutyrate) with different polydiols and polytriol) and blending of polyurethanes with small amount of polylactide influence on crystallinity and surface topography of obtained polyurethanes.     

Simultaneous separation of 14 antiarrhythmic drugs and determination of mexiletine and flecainide by capillary zone electrophoresis

A method using capillary zone electrophoresis was developed for the simultaneous separation of 14 antiarrhythmic drugs belonging to various classes. The drugs are separated on a fused-silica capillary, 90 cm x 75 microm (72 cm effective length), with phosphate and acetate buffers as background electrolytes and UV detection at 217 nm. The effects of buffer pH, temperature, and applied voltage on the migration of the drugs were studied. The pH was found to be the most significant factor determining effective separation. The antiarrhythmic compounds are completely separated within a relatively short time (< 7 min) by using 70 mM phosphate buffer at pH 7.91, an applied voltage of 28 kV, and a temperature of 32 degrees C. Mexiletine (MEX) and flecainide (FLE) were quantified under conditions of the optimum separation. The calibration graphs were constructed over the concentration range of 4.0-14.0 microg/mL for both drugs with good correlation (r > or = 0.9999). Detection and quantitation limits were found to be 0.5 and 1.5 microg/mL for FLE and 0.7 and 2.1 microg/mL for MEX, respectively. The proposed method was used for the determination of both drugs in their commercial forms with satisfactory precision (relative standard deviations of 0.36-1.21% for FLE and 0.78-1.66% for MEX) and accuracy (relative standard errors of 0.13-1.17% for FLE and 0.35-1.18% for MEX).     

Degradation Study of Polymers from Renewable Resources and their Compositions in Industrial Composting Pile

Summary: Polyesters produced from renewable resources and susceptible to hydrolysis under the industrial composting conditions offer ecological advantages as compared to thermoplastics polymers and elastomers produced from fossil carbon sources. In this paper the degradation behaviour of polymer compositions of BTA, PLA and a-PHB in natural environment of industrial composting pile, consisting of leaves - 40%, branches - 30% and grass - 30%, have been presented. The extend of degradation was monitored by macroscopic observations of sample surfaces, changes of molecular weight, polydispersity and composition of the tested materials and their weight loss.