Synthesis of N-heterocyclic ligands for use in affinity and mixed mode chromatography

A set of heterocyclic ligands have been synthesised for use in the preparation of mixed mode affinity chromatographic adsorbents for application in the purification of proteins, including antibodies. The ligand structures were designed to consist of a pyridinyl or related aza-heterocyclic nucleus bearing a pendant arm containing either an alkylamine, alkylthiol or hydroxyalkyl nucleophilic group to allow their facile immobilisation onto an activated support matrix. Ligand diversity was achieved by altering the length of the alkyl chain between the heterocyclic nucleus and nucleophilic group, varying the position of alkyl chain attachment to the heterocycle, and incorporating extra substituents into the pyridinyl or related aza-heterocyclic ring. This diversity in ligand structure was intended to enable key structural features of the ligand, required for efficient protein binding, to be determined. In contrast to the previously used multi-step procedures for the preparation of analogous substituted pyridine or aza-heterocyclic compounds, the synthesis routes for the ligands described here have generally utilized very mild, one-step reactions with readily available heterocyclic precursors.     

Zone trapping/merging zones in flow analysis: a novel approach for rapid assays involving relatively slow chemical reactions

A novel strategy for accomplishing zone trapping in flow analysis is proposed. The sample and the reagent solutions are simultaneously inserted into convergent carrier streams and the established zones merge together before reaching the detector, where the most concentrated portion of the entire sample zone is trapped. The main characteristics, potentialities and limitations of the strategy were critically evaluated in relation to an analogous flow system with zone stopping. When applied to the spectrophotometric determination of nitrite in river waters, the main figures of merit were maintained, exception made for the sampling frequency which was calculated as 189 h⁻¹, about 32% higher relatively to the analogous system with zone stopping. The sample inserted volume can be increased up to 1.0 mL without affecting sampling frequency and no problems with pump heating or malfunctions were noted after 8-h operation of the system. In contrast to zone stopping, only a small portion of the sample zone is halted with zone trapping, leading to these beneficial effects.     

Performance of a Halo Ion Trap Mass Analyzer with Exit Slits for Axial Ejection

The halo ion trap (IT) was modified to allow for axial ion ejection through slits machined in the ceramic electrode plates rather than ejecting ions radially to a center hole in the plates. This was done to preserve a more uniform electric field for ion analysis. An in-depth evaluation of the higher-order electric field components in the trap was also performed to improve resolution. The linear, cubic and quintic (5th order) electric field components for each electrode ring inside the IT were calculated using SIMION (SIMION version 8, Scientific Instrument Services, Ringoes, NJ, USA) simulations. The preferred electric fields with higher-order components were implemented experimentally by first calculating the potential on each electrode ring of the halo IT and then soldering appropriate capacitors between rings without changing the original trapping plate design. The performance of the halo IT was evaluated for 1% to 7% cubic electric field (A ₄/A ₂) component. A best resolution of 280 (m/Δm) for the 51-Da fragment ion of benzene was observed with 5% cubic electric field component. Confirming results were obtained using toluene, dichloromethane, and heptane as test analytes.     

Tandem Transesterification–Esterification Reactions Using a Hydrophilic Sulfonated Silica Catalyst for the Synthesis of Wintergreen Oil from Acetylsalicylic Acid Promoted by Microwave Irradiation

SiO₂–SO₃H, with a surface area of 115 m²/g and pore volume of 0.38 cm³g⁻¹, and 1.32 mmol H⁺/g was used as a 20% w/w catalyst for the preparation of methyl salicylate (wintergreen oil or MS) from acetylsalicylic acid (ASA). A 94% conversion was achieved in a microwave reactor over 40 min at 120 °C in MeOH. The resulting crude product was purified by flash chromatography. The catalyst could be reused three times.     

Mercapto-modified copolymers in polymer blends, 1. Functionalization of EPDM with mercapto groups and its use in NBR/EPDM blends

Ethylene-propylene-diene rubber (EPDM) was reacted with thioacetic acid in the presence of 2,2′-azoisobutyronitrile (AIBN), giving rise to thioacetate-modified EPDM (EPDMTA). The extent of the incorporation was studied as a function of both thioacetic acid and AIBN concentration and reaction time. The products were analyzed by FTIR spectroscopy, sulfur content, and ¹H NMR spectroscopy. The hydrolysis of EPDMTA in a NaOH methanolic solution resulted in mercapto-modified EPDM (EPDMSH). The addition of 5 wt.-% of this functionalized copolymer to a sulfur-vulcanized nitrile rubber (NBR)/EPDM (70 : 30 wt.-%) blend accelerated the vulcanization process as indicated by oscillating disk rheometer analysis. In addition, an improvement of mechanical and ageing properties was also observed.     

Dielectric relaxations in polymers containing dioxacyclohexane rings by thermostimulated depolarization currents

The dielectric activity of poly{5-[(methacryloxy)methyl]-5-ethyl-1,3-dioxacyclohexane} (PMAMED) and poly[(5-methacryloxy)-1,3-dioxacyclohexane] (PMAD) in the glassy region and in the glass-rubber transition is investigated by using global and partial thermostimulated discharge current (TSDC) techniques. The global TSDC curve for each polymer displays an ostensible β absorption in the glassy region followed in increasing order of temperature for a prominent α glass rubber relaxation. Partial depolarisation curves show in detail the regions of the glassy state in which more dielectric activity occurs. The TSDC curves for PMAMED are compared with those of its acrylate homologous, poly{5-[(acryloxy)methyl]-5-ethyl-1,3-dioxacyclohexane} (PAMED), finding that the methyl group in the former polymer only hinders long range micro-Brownian motions in the chains, thus shifting the glass-rubber relaxation to higher temperatures, without affecting in a significant way molecular motions in the glassy region. Small changes in the neighbourhood of the 1,3-dioxacyclohexane ring, such as suppression of a methylene group or replacement of the equatorial hydrogen in position 2 of the ring for a phenyl group, depresses the dielectric activity and shifts the β absorptions to lower temperatures. The interconversion between TSDC and a.c. dielectric results in the glassy region is discussed.