A novel approach to collision-induced dissociation (CID) for ion mobility-mass spectrometry experiments

Collision induced dissociation (CID) combined with matrix assisted laser desorption ionization-ion mobility-mass spectrometry (MALDI-IM-MS) is described. In this approach, peptide ions are separated on the basis of mobility in a 15 cm drift cell. Following mobility separation, the ions exit the drift cell and enter a 5 cm vacuum interface with a high field region (up to 1000 V/cm) to undergo collisional activation. Ion transmission and ion kinetic energies in the interface are theoretically evaluated accounting for the pressure gradient, interface dimensions, and electric fields. Using this CID technique, we have successfully fragmented and sequenced a number of model peptide ions as well as peptide ions obtained by a tryptic digest. This instrument configuration allows for the simultaneous determination of peptide mass, peptide-ion sequence, and collision-cross section of MALDI-generated ions, providing information critical to the identification of unknown components in complex proteomic samples.     

A novel fluorescent probe for zinc ion based on boron dipyrromethene (BODIPY) chromophore

ZnAB has the combined structure of N,N-bis(2-pyridylmethyl)ethylenediamine as a specific chelater for Zn(2+) and 1,3,5,7-tetramethyl-8-phenyl-boron dipyrromethene as a fluorophore. Complexation of ZnAB with Zn(2+) produces a remarkable enhancement of fluorescence intensity. ZnAB has the advantages of less sensitivity to solvent polarity and pH than fluorescein-based Zn(2+) probes. Furthermore, it is not influenced by other cations, such as Na(+), K(+), Ca(2+), and Mg(2+), which exist at high concentrations under physiological conditions, even at 2.5 mM. The results show that ZnAB is a Zn(2+) probe suitable for biological applications.     

A green deep eutectic solvent-based aqueous two-phase system for protein extracting

As a new type of green solvent, deep eutectic solvent (DES) has been applied for the extraction of proteins with an aqueous two-phase system (ATPS) in this work. Four kinds of choline chloride (ChCl)-based DESs were synthesized to extract bovine serum albumin (BSA), and ChCl-glycerol was selected as the suitable extraction solvent. Single factor experiments have been done to investigate the effects of the extraction process, including the amount of DES, the concentration of salt, the mass of protein, the shaking time, the temperature and PH value. Experimental results show 98.16% of the BSA could be extracted into the DES-rich phase in a single-step extraction under the optimized conditions. A high extraction efficiency of 94.36% was achieved, while the conditions were applied to the extraction of trypsin (Try). Precision, repeatability and stability experiments were studied and the relative standard deviations (RSD) of the extraction efficiency were 0.4246% (n = 3), 1.6057% (n = 3) and 1.6132% (n = 3), respectively. Conformation of BSA was not changed during the extraction process according to the investigation of UV–vis spectra, FT-IR spectra and CD spectra of BSA. The conductivity, dynamic light scattering (DLS) and transmission electron microscopy (TEM) were used to explore the mechanism of the extraction. It turned out that the formation of DES–protein aggregates play a significant role in the separation process. All the results suggest that ChCl-based DES-ATPS are supposed to have the potential to provide new possibilities in the separation of proteins.     

A viscoelastic description of the glass transition-conversion relationship for reactive polymers

The glass transition temperature,T _g is a sensitive and practical parameter for following cure of reactive thermosetting systems. A new equation was developed for predicting theT _g -conversion relationship based on the Dillman-Seferis viscoelastic compliance model. It assumes that the changes inT _g are primarily due to changes in relaxation time as chain extension and crosslinking reduce the mobility of a polymer network. Such information is essential in combining kinetic and viscoelastic measurements, which monitor transformations of thermosets during cure. The equation derived from the viscoelastic model was shown to be applicable for a variety of experimental data. The success of the methodology was further demonstrated by comparing well-established relations, such as the Fox equation and the Di-Benedetto equation, to predictions made possible by adjusting two viscoelastic model parameters. Finally, the fitting power of the proposed equation was shown by fitting published epoxy data from the literature as well as experimental data on a relatively new resin system such as dicyanates used as a model in this study.Der GlasumwandlungspunktT _g ist eine empfindliche und praktische Grö\e zum Verfolgen der AushÄrtung reaktiver Duroplaste. Basierend auf dem viskoelastischen Steifigkeitsmodell von Dillman-Seferis wurde eine neue Gleichung zur Vorhersage der Beziehung zwischenT _g und Konversion entwickelt. Dabei wird angenommen, da\ die Änderung vonT _g in erster Linie durch eine Änderung der Relaxationszeit bedingt ist, da KettenverlÄngerung und Vernetzung die Beweglichkeit des Polymergefüges herabsetzen. Bei einer Kombination von kinetischen und viskoelastischen Messungen, mit denen die Umwandlungen wÄhrend des AushÄrtens von Duroplasten verfolgt werden können, ist diese Erkenntnis von gro\er Bedeutung. Die auf der Basis des viskoelastischen Modelles erhaltene Gleichung ist für eine gro\e Breite von experimentellen Daten anwendbar. Den Erfolg dieser Methodik zeigt weiterhin ein Vergleich bewÄhrter Beziehungen, wie z.B. der Foxschen Gleichung und der Gleichung von DiBenedetto, mit Aussagen, die durch Anpassung zweier viskoelastischer Parameter ermöglicht wurden. Die StÄrke der vorgeschlagenen Gleichung wird letztlich durch Anpassen von Epoxy-Daten aus der Literatur sowie von experimentellen Daten eines relativ neuen und in dieser Untersuchung als Modell benutzten Harzsystemes gezeigt.     

A novel poly(deep eutectic solvent)-based magnetic silica composite for solid-phase extraction of trypsin

Novel poly(deep eutectic solvent) grafted silica-coated magnetic microspheres (Fe₃O₄@SiO₂-MPS@PDES) were prepared by polymerization of choline chloride-itaconic acid (ChCl-IA) and γ-MPS-modified magnetic silica composites, and were characterized by vibrating sample magnetometer (VSM), Fourier transform infrared spectrometry (FT-IR), X-ray photoelectron spectra (XPS), thermal gravimetric analysis (TGA) and transmission electron microscope (TEM). Then the synthetic Fe₃O₄@SiO₂-MPS@PDES microspheres were applied for the magnetic solid-phase extraction (MSPE) of trypsin for the first time. After extraction, the concentration of trypsin in the supernatant was determined by a UV–vis spectrophotometer. Single factor experiments were carried out to investigate the effects of the extraction process, including the concentration of trypsin, the ionic strength, the pH value, the extraction time and the temperature. Experimental results showed the extraction capacity could reach up to 287.5 mg/g under optimized conditions. In comparison with Fe₃O₄@SiO₂-MPS, Fe₃O₄@SiO₂-MPS@PDES displayed higher extraction capacity and selectivity for trypsin. According to the regeneration studies, Fe₃O₄@SiO₂-MPS@PDES microspheres can be recycled six times without significant loss of its extraction capacity, and retained a high extraction capacity of 233 mg/g after eight cycles. Besides, the activity studies also demonstrated that the activity of the extracted trypsin was well retained. Furthermore, the analysis of real sample revealed that the prepared magnetic microspheres can be used to purify trypsin in crude bovine pancreas extract. These results highlight the potential of the proposed Fe₃O₄@SiO₂-MPS@PDES-MSPE method in separation of biomolecules.     

A novel green biosorbent from chitosan modified by sodium phytate for copper (II) ion removal

A novel kind of adsorbent bead was prepared from chitosan (CS) by ionic‐linked with sodium phytate (SP) and then covalent cross‐linked with epichlorohydrin (ECH) by nonsolvent‐induced phase separation. The structure of the beads was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and X‐ray photoelectron spectroscopy. The adsorption properties of the beads for Cu(II) ions under different adsorption conditions were investigated. The maximum adsorption capacity of Cu(II) ions was 177.1 mg g⁻¹ at the conditions of pH of 5.2, temperature of 50°C, and initial Cu(II) ion concentration of 728.3 mg L⁻¹. The adsorption isotherm of Cu(II) ions on the CS/SP/ECH beads was well correlated with the Langmuir isotherm model, and the whole adsorption process could be better followed the pseudo‐second‐order kinetic model. Moreover, the CS/SP/ECH beads still exhibited good adsorption capacity even after the 15th regeneration cycles.     

Sensitivity enhancement using chemically reactive gas cluster ion beams in secondary ion mass spectrometry (SIMS)

We report for the first time on significant molecular secondary ion yield increases by modifying the chemistry of a water cluster primary ion beam. This was demonstrated using 70-keV ion beams of 0.15 eV/amu. For the neutral drug Bezafibrate, secondary ion yield enhancements ×5–10 were observed when replacing the Ar carrier gas in a water gas cluster ion beam (GCIB) source with a mixture containing 12% CO₂ and 2% O₂ in Ar. For the cationic drug Ranitidine, the ion yield enhancements using the CO₂-containing carrier gas were up to ×20–50 in positive mode and ×2–4 in negative mode. The extent of molecular fragmentation was very similar from both cluster beams. We conclude that additional chemically reactive species are present in the impact zone using the (H₂O/CO₂)_n projectile, which promote the formation of secondary ions of both polarity through projectile impact-induced chemical reactions. This methodology can be applied to further extend the capabilities of high-resolution 3-dimensional mass spectral imaging using reactive GCIB-SIMS.     

A novel synthesis of (di)-benzazocinones via an endocyclic N-acyliminium ion cyclisation

The triflic acid-mediated endocyclic N-acyliminium ion cyclisation provides a facile synthesis of (di)-benzazocinones. On reduction of the 10-phenyl derivative, an unusually non-polar tertiary alkylamine was obtained.     

The synthesis of novel aliphatic bis(acenaphthelene) reactive monomers

Novel aliphatic‐bridged bis(acenaphthalene)s are synthesized and evaluated as potential precursors to high‐temperature reactive monomers. It was found that as the length of the aliphatic bridging unit increased, the thermal stability of bis(acenaphthalene) increased and melting point decreased. The use of an alternative route for the introduction of the reactive vinyl group resulted in a dramatic increase in monomer purity. The increase in monomer purity resulted in the creation of a processing window that enabled samples to be melt cast prior to polymerization, greatly improving their suitability as high‐temperature polymers. Polymerized samples were found to have high thermal stability, indicating they have potential as high temperature materials. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43:5072–5082, 2005     

A novel ion selective sensor for promethium determination

This is a first promethium(145) ion-selective sensor based on the comparative study of two Schiff base ligands (X(1) and X(2)) as neutral ionophores. Effect of various plasticizers: 2-nitrophenyloctylether (o-NPOE), dibutyl phosphonate (DBP), dioctylphthalate (DOP), tri-(2-ethylhexyl) phosphate (TEHP), dibutyl butylphosphonate (DBBP), chloronaphthalene (CN) and anion excluders: potassium tetrakis (p-chloropheny1) borate (KTpClPB), sodiumtetraphenylborate (NaTPB) and oleic acid (OA) have been studied. The membrane with a composition of ionophore (X(1)/X(2)):KTpClPB:PVC:o-NPOE (w/w, %) in the ratio of 5:5:30:60 exhibited best performance. The best responsive membrane sensors (8 and 21) exhibited working concentration range of 4.5×10(-7)-1.0×10(-2) M and 3.5×10(-6)-1.0×10(-2) M with a detection limits of 3.2×10(-7) M and 2.3×10(-6) M and Nernstian slopes of 20.0±0.5, 19.5±0.5 mV decade(-1) of activity, respectively. The sensor no. 8 works satisfactorily in partially non-aqueous media up to 10% (v/v) content of methanol, ethanol and acetonitrile. Analytical application of the proposed sensor has been demonstrated in determination of promethium (III) ions in spiked water samples.     

A novel approach for coincidence ion mass spectrometry

A novel approach is proposed for extracting a maximum of information from secondary ions ejected when surfaces are bombarded with keV mono or polyatomic ions. It is known that the event-by-event bombardment-detection mode allows identification of spatiotemporal relationships among individual secondary ions which in turn reveal surface composition within nanometric dimensions. We have devised a procedure for identifying spatiotemporal relationships among individual secondary ions without the requirement of pulsed sample interrogation (one single projectile at a time). The consequence of "mass separated time-of-flight mass spectrometry" is a much improved measurement duty cycle.     

A novel ion selective membrane potentiometric sensor for direct determination of Fe(III) in the presence of Fe(II)

A new PVC membrane potentiometric sensor that is highly selective to Fe(III) ions was prepared by using 2-[(2-hydroxy-1-propenyl-buta-1,3-dienylimino)-methyl]-4-p-tolylazo-phenol [HPDTP] as a suitable carrier. The electrode exhibits a linear response for iron(III) ions over a wide concentration range (3.5 × 10⁻⁶ to 4.0 × 10⁻²) with a super Nernstian slope of 28.5 (±0.5) per decade. The electrode can be used in the pH range from 4.5 to 6.5. The proposed sensor shows fairly a good discriminating ability towards Fe³⁺ ion in comparison to some hard and soft metals such as Fe²⁺, Cd²⁺, Cu²⁺, Al³⁺ and Ca²⁺. It has a response time of <15 s and can be used for at least 2 months without any measurable divergence in response characteristics. The electrode was used in the direct determination of Fe³⁺ in aqueous samples and as an indicator electrode in potentiometric titration of Fe(III) ions.     

1-Pyrenecarboxaldehyde thiosemicarbazone:A novel fluorescent molecular sensor towards mercury(Ⅱ) ion

<正>A novel and simple fluorescent molecular sensor,1-pyrenecarboxaldehyde thiosemicarbazone(Hpytsc),was synthesized.Its higher sensitivity and selectivity to mercury(Ⅱ) ion were studied through absorption and emission channels.The UV-vis spectra show that the increasing mercury(Ⅱ) ion concentrations result in the decreasing absorption intensity.The fluorescence monomer emission of Hpytsc is enhanced upon binding mercury(Ⅱ) ion,which should be due to the 1:1 complex formation between Hpytsc and metal ion.     

Simple fitting of energy-resolved reactive cross sections in threshold collision-induced dissociation (T-CID) experiments

An operationally much simpler method for the extraction of thermochemical data from energy-resolved collision-induced dissociation cross sections, which is specifically designed for ligand binding energy determinations by tandem mass spectrometry, is presented. Compared to previous methods available in the literature, the present method has three advantages: (i) A more realistic treatment of the electrostatic potential for the approach of the ion to the collision partner leads to a better, nonempirical threshold function, allowing fitting of the cross section over the entire energy range rather than just the onset. (ii) Treatment of the kinetic shift with a new model for the density-of-states function eliminates the need for explicit entry of frequencies for the starting ion or the transition state without loss of accuracy relative to direct state counts. (iii) Data fitting using Monte Carlo simulation and a genetic algorithm instead of the usual Marquardt-Levenburg least-squares routines not only produces an equivalent fit but also produces statistically relevant error bounds on the derived fit parameters. Although the method is conceived for medium-to-large organometallic complexes, the theory is general enough to be appropriate for a wide range of binding phenomena of a small molecule to a larger one observed in mass spectrometry.     

A chemiluminescence flow injection system for nitrite ion determination

A chemiluminescence system is described for the determination of nitrite ion based on new designs for an ozone generator, liquid-gas separator and chemiluminescence reaction cell. The method is based on the gas-phase chemiluminescence reaction between ozone and nitric oxide, which is generated from the reduction of nitrite with iodide in sulfuric acid solution. The efficiency of the system was evaluated by investigation of the analytical performance characteristics of the system for nitrite determination in batch and flow injection procedures. Under optimal conditions, the chemiluminescence response of the system was linear against the nitrite concentration over the range 1 to 1 × 10⁴ ng ml^?1 in the batch procedure and 10 to 5 × 10³ ng ml^?1 in the flow injection procedure, with detection limits of 1 and 10 ng ml^?1, respectively. The method is highly selective and allows for the determination of nitrite in the presence of high concentrations of several cationic, anionic and nitrogen containing species. It has been successfully applied to the analysis of nitrite in natural water and soil extracts.     

A novel non-radioactive electron source for ion mobility spectrometry

Typical ion mobility spectrometers work by employing a radioactive source to provide electrons with high energy to ionize the analytes in a series of chemical reactions. General security as well as regulatory concerns related to the use of radioactivity resulted in a need for a different ionization source which on the other hand produces ions in a similar manner as a radioactive source because the mechanisms are well known. Here we introduce a novel non-radioactive electron source which is capable of providing high energy electrons in a way that is similar to beta radiating substances yielding correspondingly similar peak spectra.     

A novel flow injection chemiluminescence determination of Cr(VI) with Dichlorotris(1,10-phenanthroline)ruthenium(II)

A selective novel reverse flow injection system with chemiluminescence detection (rFI-CL) for the determination of Cr(VI) in presence of Cr(III) with Dichlorotris (1,10-phenanthroline)ruthenium(II), (Ru(phen)₃Cl₂), is described in this work. This new method is based on the oxidation capacity of Cr(VI) in H₂SO₄ media. First, the Ruthenium(II) complex is oxidized to Ruthenium(III) complex by Cr(VI) and afterwards it is reduced to the excited state of the Ruthenium(II) complex by a sodium oxalate solution, emitting light inside the detector. The intensity of chemiluminescence (CL) is proportional to the concentration of Cr(VI) and, under optimum conditions, it can be determined over the range of 3-300 μg L⁻¹ with a detection limit of 0.9 μg L⁻¹. The RSD was 8.4% and 1.5% at 5 and 50 μg L⁻¹, respectively. For the rFI-CL method various analytical parameters were optimized: flow rate (1 mL min⁻¹), H₂SO₄ carrier concentration (20% w/V), Ru(phen)₃Cl₂ concentration (5 mM) and sodium oxalate concentration (0.1 M). The effect of Cr(III), Fe(III), Al(III), Cd(II), Zn(II), Hg(II), Pb(II), Ca(II) and Mg(II), was studied. The method is highly sensitive and selective, allowing a fast, on-line determination of Cr(VI) in the presence of Cr(III). Finally, the method was tested in four different water samples (tap, reservoir, well and mineral), with good recovery percentage.     

A novel surface ionization source for ion mobility spectrometer

A surface ionization (SI) source is designed and prepared for ion mobility spectrometer (IMS). The source acts not only as an emitter but also an ion injector which can inject ions periodically into the drift region of drift tube. Using the dual-role source, the dimension of the drift tube can be decreased and the circuit for high voltage can be simplified efficiently. The IMS with the SI source has a response range of ∼4 orders of magnitude and a good reproducibility to tri-ethylamine. Compared with radioactive ionization (RI), the ultra-short time for ion injection and the zero level base line of ion mobility spectrum are characteristics of the surface ionization.     

Struik law for enthalpy retardation at the glass transition in poly(n-alkylmethacrylates) measured by DSC aging experiments

Results of calorimetric (DSC) experiments on a series of poly (n-alkylmethcrylates), from methyl to pentyl, after different aging timest _e at different aging temperaturesT _e are presented. The aging behavior is quite different from that in other polymers, for example PS. For all poly(n-alkylmethacrylates) investigated the aging peak temperatureT _max is shifted parallel to the aging temperatureT _e in a large temperature interval below the glass temperature. The results are discussed with respect to shear and entropy response in the splitting region.