Displacer concentration effects in displacement chromatography: Implications for trace solute detection

In this paper, the utility of ion-exchange displacement chromatography for the concentration and enrichment of trace proteins is examined. Separations with varying displacer concentrations (1–25 mM neomycin sulfate) indicate that higher concentrations result in elevated protein concentrations, at the price of reduced yields. The results demonstrate that displacement chromatography carried out at relatively low displacer concentrations (2.5 mM) can produce significant concentration (8.5-fold) and enrichment (18-fold) of trace proteins present in the feed. Parametric simulations using the steric mass action model are carried out to investigate the concentration effects and enrichment factors observed over a wide range of feed, displacer and buffer counter-ion concentrations, and solute separation factors. The simulations confirm that trace components can be readily concentrated and enriched by displacement chromatography and that these effects will be more pronounced as the separation factor between trace and abundant components is increased. The results presented in this paper indicate the potential of displacement chromatography for improved separations where trace enrichment is critical such as proteomic applications.     

Zirconium phosphate dispersed on a cellulose fiber surface: preparation, characterization, and selective adsorption of Li+, Na+, and K+ from aqueous solution

Highly dispersed zirconium phosphate was prepared by reacting Cel/ZrO(2) (ZrO(2)=6.7 wt%; 0.56 mmol g(-1) of zirconium atom per gram of the material) with phosphoric acid. High power decoupling magic angle spinning (HPDEC-MAS)(31)P NMR and X-ray photoelectron spectroscopy data indicated that HPO(2-)(4) is the species present on the fiber surface. The X-ray diffraction patterns showed that zirconium hydrogen phosphate particles were amorphous and had an ion-exchange capacity, determined by ammonia gas adsorption, of 0.30 mmol g(-1). The ion-exchange capacities for Li(+), Na(+), and K(+) ions were determined from ion-exchange isotherms at 298 K and showed the following values (in mmol g(-1)): Li(+)=0.01, Na(+)=0.23, and K(+)=0.30. The higher affinity of the surface hydrogen phosphate particles for Na(+) and K(+) is due to its lamelar structure which permits easier diffusion of these two ions whose hydrated radii are smaller than that of Li(+).     

Microcellular foams from polyethersulfone and polyphenylsulfone: Preparation and mechanical properties

Polymeric foams having microcellular structures were successfully prepared from some high-performance thermoplastics, specifically polyethersulfone and polyphenylsulfone. A two-stage batch foaming process was used and the resulting materials had average cell sizes in the range 2-13 μm, and cell densities the order of 10¹⁰-10¹¹ cells/cm³. The foam densities (relative to those of the unfoamed polymers) were in the range 0.90-0.35. Average cell sizes increased with foaming temperature and foaming time; on the other hand, cell densities and relative foam densities decreased slightly with foaming temperature but remained almost constant with foaming time. Experimental values of Young’s modulus in compression and the elastic collapse strength were higher than theoretically predicated at high relative densities, but the discrepancies became small at lower densities. In contrast, Young’s moduli in tension were in very good agreement with theory, but the relative strengths were somewhat lower than predicated.     

Molecular design, characterization, and application of multiinformation dyes for optical chemical sensing: IV. Multiinformation dyes with extended spectral sensitivity in the near-infrared spectral range

In this paper, new “multiinformation dyes” (MIDs) with extended spectral sensitivity reporting on both changes in solvent polarity (solvatochromism) and in pH (halochromism) by changes in their visible absorption spectra, are presented. The merocyanine dyes 2,6-dibromo-4-[4-(1-dodecyl-4(1H)-pyridinylidene)-2-butenylidene]-2,5-cyclohexadien-1-one (KD-M301) and 2,6-dibromo-4-[4-(1-dodecyl-4(1H)-quinolinylidene)-2-butenylidene]-2,5-cyclohexadien-1-one (KD-M402) were designed, synthesized, and characterized regarding analytical applications. The spectral sensitivity for the MIDs was extended into the near-infrared (NIR) wavelength range (λ_max=800 nm in CHCl₃ for KD-M402) and at the same time, the degree of solvent polarity-induced spectral shifts was strongly enhanced (Δλ_max=202 nm for KD-M402 between tetrahydrofuran (THF) and methanol), reaching similar values to the standard solvatochromic dye Dimroth-Reichardt’s betaine on which the empirical E_T(30) classification of solvent polarity is based. Compared to Dimroth-Reichardt’s betaine dye, the molar absorption coefficient ε, is increased more than 10-fold (ε of KD-M402 in THF: 7.7×10⁴ M⁻¹ cm⁻¹), allowing sensitive measurements at low concentrations of the dye. The dodecyl-substituted KD-M402 is suitable as a lipophilic pH indicator in ion-exchange type optical sensors (optodes) with optical detection in the near-infrared wavelength range.     

In situ continuous monitoring of chloride, nitrate and ammonium in a temporary stream: Comparison with standard methods

A multi-parameter probe was used for in situ chloride, nitrate and ammonium measurements in a temporary stream (Ribeira da Pardiela, in the South of Portugal). Comparison with standard analytical methods was performed for all elements. For chloride, the results of the probe depicted the same behaviour as that obtained with the standard method, although it is clear that the matrix effects were present. For nitrate, the results obtained with the probe were in agreement with the other standard methods used, except for samples collected during drought, when the stream water became brownish and exhaled an offensive smell, due to the decomposition of organic matter. For ammonium, surprisingly the probe show to be the best option, the phenate method being affected by matrix effects. The results still suggest an interference of the bicarbonate ion on nitrate determination, but standard additions approach was shown to minimize most of the matrix effects. Recoveries were reasonable to good for all the three anions under scrutiny.     

Synthesis of triarylphosphines having para -SH and -SMe groups: Preparation of their complexes and formation of a monolayer on a gold surface

The phosphines P(C₆H₄-4-SR)₃ (R = H, Me, 2-C₅H₉O) and (C₆H₄-4-SR)₂PCH₂CH₂P(C₆H₄-4-SR)₂ (R = H, Me) have been synthesized. The phosphines with -SMe groups can be prepared by reaction of 4-BrC₆H₄SMe with either BuLi or magnesium (to generate the corresponding Grignard compound) followed by reaction with PCl₃ or Cl₂PCH₂CH₂PCl₂, respectively. The methyl group can be eliminated by reaction with sodium in liquid NH₃. Other methods of protection/deprotection of the thiol group failed to afford the desired compounds. Reaction of 4-BrC₆H₄SH with dihydropyrane afforded the protected thiol 4-BrC₆H₄S-2-C₅H₉O from which the corresponding phosphine was successfully synthesized. However, attempts to remove the tetrahydropyranyl group by reaction with AgNO₃-HCl, gave an insoluble polymer as product. Reaction of P(C₆H₄SR)₃ (R = H, Me) with Ni(CO)₄ affords the corresponding mono phosphine complex quantitatively. The complex with the unprotected thiol group can be absorbed on a gold surface and the corresponding ν_CO bands were detected by grazing angle Fourier transform infrared reflection absorption spectroscopy (grazing angle FTIR-RAS). Reaction of Rh(acac)(CO)₂ with P(C₆H₄SR)₃ (R = Me) affords the complex Rh(acac)(CO)(P(C₆H₄SR)₃) (R = Me), but if R = H a polymer insoluble in any solvent was obtained. The same occurs in the case of PtCl₂(CO)(DMSO). Apparently, once P(C₆H₄SH)₃ is coordinated to a metal not in the zero oxidation state, oxidation of the thiol group to disulphide becomes very easy even in a dinitrogen atmosphere.     

Challenges in modelling and optimisation of stability constants in the study of metal complexes with monoprotonated ligands: Part I. A glass electrode potentiometric and polarographic study of a Cu-TAPSO-OH system

The behaviour of solutions containing 3-(N-tris[hydroxymethyl]methylamine)-2-hydroxypropanesulfonic acid (TAPSO) and copper(II) was studied by two analytical techniques, direct current polarography (DCP) and glass electrode potentiometry (GEP), at fixed total TAPSO to total copper(II) concentration ratios and various pH values, at 25 °C and ionic strength 0.1 M KNO₃. DCP and GEP, when used independently, were not able to provide a final metal-ligand model. Combined interpretation of data from DCP and GEP indicated the formation of six main species, CuL⁺, CuL(OH), CuL(OH)₂⁻, CuL₂, CuL₂(OH)⁻ and CuL₂(OH)₂²⁻ for which stability constants (as log β) were found to be 4.41, 11.43, 17.55, 8.08, 14.3 and 20.3, respectively. Five of these complexes, CuL(OH), CuL(OH)₂⁻, CuL₂, CuL₂(OH)⁻ and CuL₂ (OH)₂²⁻ are reported for the first time.     

Mixed ligands supported yttrium alkyl complexes:: Synthesis, characterization and catalysis toward lactide polymerization

Treatment of yttrium tris(alkyl)s, Y(CH₂SiMe₃)₃(THF)₂, by equimolar H(C₅Me₄)SiMe₃(HCp′) and indene (Ind-H) afforded (η⁵-Cp′)Y(CH₂SiMe₃)₂(THF) (1) and (η⁵-Ind)Y(CH₂SiMe₃)₂(THF) (2) via alkane elimination, respectively. Complex 1 reacted with methoxyamino phenols, 4,6-(CH₃)₂-2-[(MeOCH₂CH₂)₂-NCH₂]-C₆H₂-OH (HL¹) and 4,6-(CMe₃)₂-2-[(MeOCH₂CH₂)₂-NCH₂]-C₆H₂-OH (HL²) gave mixed ligands supported alkyl complexes [(η⁵-Cp′)(L)]Y(CH₂SiMe₃) (3: L = L¹; 4: L = L²). Whilst, complex 2 was treated with HL² to yield [(η⁵-Ind)(L²)]Y(CH₂SiMe₃) (5). The molecular structures of 3 and 5 were confirmed by X-ray diffraction to be mono(alkyl)s of THF-free, adopting pyramidal and tetragonal-bipyramidal geometry, respectively. Complexes 3 and 5 were high active initiators for the ring-opening polymerization of l-lactide to give isotactic polylactide with high molecular weight and narrow to moderate polydispersity.     

Development of a group-specific immunoassay for sulfonamides: Application to bee honey analysis

A set of haptens has been synthesized in order to raise generic polyclonal antibodies against sulfonamides using different strategies. After the screening of all the immunorreagents, a highly sensitive enzyme-linked immunosorbent assay was set-up for simultaneous determination of six of these antibiotics.The developed procedure allows the screening of: sulfathiazole, sulfamethoxypyridazine, sulfapyridine, sulfamethizole, sulfasalazine and N⁴-phtalylsulfathiazole with good accuracy and precision at level 0.13 ng mL⁻¹ in buffer.The suitability of developed ELISA for its application to honey analysis has been investigated. The antimicrobials were extracted from samples with acetate buffer, and cleaned up by solid phase extraction. The mean recovery found for honey samples, spiked from 1.5 to 4.5 ng mL⁻¹ equivalents of sulfathiazole (24-72 μg sulfathiazole kg⁻¹ honey), was 106%.     

Analysis of polyethoxylated surfactants in microemulsion-oil-water systems: III. Fractionation and partitioning of polyethoxylated alcohol surfactants

Oligomer distribution of polyethoxylated alcohol and polyethoxylated nonylphenol surfactants is studied by normal and reverse-phase high performance liquid chromatography (HPLC). A RP8 column is able to efficiently separate these surfactants according to their alkyl chain (lipophilic) group, while silica and amino columns separate them according to their polyether chain length (hydrophilic group). Polyethoxylated alcohol and polyethoxylated nonylphenol oligomers selectively partition between the microemulsion-oil-water phases of a Winsor III system. Partitioning of these oligomers was analyzed by HPLC with RI detection. The logarithm of the partition coefficient between the water and oil linearly increases with the number of ethylene oxide groups per molecule of oligomer. For a same ethoxylation degree, the partition coefficient of a polyethoxylated tridecanol is found to be higher than the one of the corresponding nonylphenol specie. On the other hand, a polyethoxylated nonylphenol exhibits a higher solubilization than the matching polyethoxylated alcohol.     

New hydrofluorocarbon (HFC) solvents for antimony pentafluoride: Generation and characterization of 1-alkoxypentafluoroallyl cations

Certain hydrofluorocarbons (HFC) stable towards the strong Lewis acid, antimony pentafluoride, were found to function as a solvent for this aggressive reagent. CF₃CF₂CH₂F (HFC-236cb) was demonstrated to be an excellent solvent for SbF₅ and was used for the generation of stable polyfluorinated benzyl and allyl cations. Using this solvent 1-methoxypentafluoroallyl cation and R_FOCFCFCF₂⁺ (R_F = n-C₃F₇ and n-C₄F₉), were generated and characterized by NMR spectroscopy.     

Custom synthesis of molecular imprinted polymers for biotechnological application: Preparation of a polymer selective for tylosin

A molecularly imprinted polymer (MIP) selective for tylosin was designed and synthesised using a computational method (MIP “dialling”). In re-binding experiments the MIP demonstrated high affinity for tylosin in aqueous solutions and in organic solvents. The synthesised polymer was tested for re-binding with the template and related metabolites such as tylactone, narbomycin and picromycin. The HPLC analysis showed that the computationally designed polymer is specific and capable of separating the template from its structural analogues. The MIP was capable of recovering tylosin from broth samples. The polymer capacity for tylosin was estimated as 6.4 mg/g for MIP, which was suitable for practical application and tylosin recovery from broth samples. Among the advantages of this was the possibility to adsorb tylosin from a complex media with easy removal of oils and other impurities which are present in significant quantities, which can create problems for its chromatographic purification procedure. The MIP “dialling” procedure can have a general significance for the fast preparation of specific adsorbents for biotechnological applications.     

Treatment of turkeys with nitroimidazoles: Impact of the selection of target analytes and matrices on an effective residue control

In several animal studies turkeys were treated with different nitroimidazoles (Dimetridazole, Metronidazole, Ronidazole, Ipronidazole). After slaughtering, different matrices (breast muscle, leg muscle, liver, plasma, retina) were analysed for their analyte content, for the percentage of hydroxy-metabolites, for homogeneity, stability and bound, and conjugated residues. The tests showed that for animals treated with Dimetridazole and Ipronidazole, the hydroxy-metabolites (2-hydroxymethyl-1-methyl-5-nitroimidazole (HMMNI) and 1-methyl-2-(2′-hydroxyisopropyl)-5-nitroimidazole (IPZOH)) are the relevant target analytes, whereas for animals treated with Ronidazole and Metronidazole, the parent drug itself is the most relevant analyte. In muscle samples an inhomogeneous analyte distribution was found. Degradation studies showed a rapid decline of the analyte concentration in muscle and liver samples stored at room temperature and a decelerated degradation at 4 °C. In plasma and retina samples, however, the analytes were stable during storage under the same conditions. In these matrices the analytes were found to be present in considerably higher concentrations than in muscle or liver and could be detected for a longer period of time after withdrawal of the medication. Therefore, plasma or retina can be recommended as target matrices for the residue control of nitroimidazoles in turkeys.     

Preparation of models and oligomers of metal alkynyls: NMR, GPC and X-ray structural characterization of building blocks for the construction of molecular devices

A systematic study has been carried out for the use of the palladium-based Extended One Pot (EOP) synthetic protocol toward the preparation of metal alkynyl oligomers of general formula [CCArCCM(L)_m]_n (M=Pt, Pd). Model compounds of type trans-M(PBu₃)₂(CCC₆H₅)₂ have been prepared by the reaction of tributyltinethynylbenzene with trans-M(PBu₃)₂Cl₂, in the absence of palladium catalysis, since the presence of catalytic Pd(PPh₃)₄ yields reaction mixtures containing starting material, product and intermediate complex trans-MCl(PBu₃)₂(CCC₆H₅). Palladium catalysis has been used for the formation of the bistinacetylide compounds Bu₃SnCCArCCSnBu₃ (Ar=C₆H₄; bis(2,5-n-octyloxy)C₆H₄). Subsequent coupling of these compounds with MCl₂(PBu₃)₂ in the absence of palladium catalyst yields metal alkynyl oligomers. Comparison of ³¹P-NMR and gel permeation chromatography (GPC) analyses indicates that the GPC technique represents a reliable method to estimate polymer chain lengths for polymers bearing branched aromatic spacers, in spite of the rigid-rod shape of the polymer backbone. Single crystal X-ray determinations of model compounds demonstrate the essential role of side substituents in the aromatic ring to control the supramolecular order and, as a consequence, the optoelectronic properties of materials.     

Solubilities of lanthanum oxide in fluoride melts: Part I. Solubility in M3AlF6 (M = Li, Na, K)

Solubility of lanthanum oxide was measured by thermal analysis. The solubility in alkali cryolites is rather high, because of chemical reactions between lanthanum oxide and cryolites. In Li₃AlF₆-La₂O₃, alumina precipitates, in the other systems the mixed oxide LaAlO₃ is formed. In La₂O₃-Li₃AlF₆ the eutectic point is at 9.5 mol% La₂O₃ and 755 °C. The eutectic points in La₂O₃-Na₃AlF₆ and La₂O₃-K₃AlF₆ are at 11.5 mol% La₂O₃, and at 937 and 934 °C, respectively.     

Copolymer of maleic anhydride with 1,3-dichlorobuten: 2. Synthesis, characterization, and charge-transfer interaction with dimethyl sulfoxide

A new type of copolymer with strong electron accepting ability on the basis of maleic anhydride and 1,3-dichlorobutene-2 has been synthesized. Both solutions and solids have been investigated. It was found that the dissolution of copolymer in dimethyl sulfoxide (DMSO) leads to its transformation: charge-transfer interaction with DMSO and subsequent Pummerer rearrangement.     

Amphiphilic polymers based on higher alkylene oxides: Synthesis and characterization by different chromatographic techniques

Homopolymers and block copolymers of higher epoxides (butene oxide and hexene oxide) are synthesized using 1-alkanols and polyethylene glycol monomethyl ether (PEG-MME) 1100 as initiators by anionic ring opening polymerization in bulk. Most of the samples were synthesized with controlled microwave heating in sealed vessels. Tri- and tetrablock copolymers with different repeat units in the individual blocks are synthesized by living polymerization with addition of the next monomer after complete consumption of the previous one. The products thus obtained are characterized using size exclusion chromatography (SEC), liquid chromatography under critical conditions (LCCC) and liquid adsorption chromatography (LAC).     

Fluoroalkene chemistry: Part 3. Reactions of arylthiols with perfluoroisobutene, perfluoropropene and chlorotrifluoroethene

Reactions of perfluoroisobutene (PFIB), perfluoropropene (PFP) and chlorotrifluoroethene (CTFE) with benzenethiol and 2-methoxybenzenethiol in acetonitrile, with potassium carbonate as base, were compared. PFIB reacted with benzenethiol to give ketene thioacetal (CF₃)₂CC(SAr)₂ and with 2-methoxybenzenethiol to give mono- and bis-vinyl species (CF₃)₂CCFSAr and (CF₃)₂CC(SAr)₂. PFP reacted with both thiols to give the addition product CF₃CFHCF₂SAr and vinyl isomers CF₃CFCFSAr (6:1 E/Z ratio). CTFE reacted with several methoxy-substituted arylthiols to give addition products of structure CFClHCF₂SAr. The arylthiols used throughout the study imitate biological thiols. Inhalation toxicities of the fluoroalkenes decrease in the order PFIB > PFP > CTFE and correlate with their reactivities towards the model thiols, supporting the current view that their toxicity relates to their ability to react with biological thiols.     

Plasma modified polymers as a support for enzyme immobilization 1.: Allyl alcohol plasma

The paper describes deposition of plasma polymerized allyl alcohol on polysulfone film. It is shown that film surface becomes more hydrophilic after plasma treatment independently on presence of argon in a reaction mixture. The chemistry of the new surface layer was established by FTIR-ATR and ESCA spectroscopy. The substrate placed close to the plasma edge was the most hydrophilic but the amount of hydoxyl groups was not the highest there. Presence of argon stabilized the plasma but the deposited layer contained relatively less oxygen-bearing functionalities. The plasma treated polymer was subjected to xylose isomerase immobilization. For this purpose the divinylsulfone method was adapted. The studies revealed no correlation between the surface hydrophilicity and efficiency of immobilization.     

Photopolymerizable acrylated hyperbranched polyisophthalesters used for photorefractive materials : I. Synthesis and characterization

UV-curable acrylated hyperbranched prepolymers with different numbers of acrylic end-groups were synthesized by modifying the hyperbranched polyisophthalester (HPIPE) with hydroxyethyl acrylate and β-naphthol, and characterized by FT-IR, ¹H NMR and VPO measurements. The effect of naphthyl end-group concentration of the prepolymer on their refractive index (RI) was investigated by an Abel Refractive Apparatus. It was found that the RI increases gradually as naphthyl end-group concentration increases. The acrylate-modified HPIPEs with or without co-monomer trimethylolpropane triacrylate addition were photopolymerized rapidly in the presence of a photo-fragmenting initiator under UV irradiation. Thermal properties of the UV-cured films were also studied by DMTA and TGA measurements.