Evaluation and optimization of electron capture dissociation efficiency in fourier transform ion cyclotron resonance mass spectrometry

Electron capture dissociation (ECD) efficiency has typically been lower than for other dissociation techniques. Here we characterize experimental factors that limit ECD and seek to improve its efficiency. Efficiency of precursor to product ion conversion was measured for a range of peptide (∼15% efficiency) and protein (∼33% efficiency) ions of differing sizes and charge states. Conversion of precursor ions to products depends on electron irradiation period and maximizes at ∼5–30 ms. The optimal irradiation period scales inversely with charge state. We demonstrate that reflection of electrons through the ICR cell is more efficient and robust than a single pass, because electrons can cool to the optimal energy for capture, which allows for a wide range of initial electron energy. Further, efficient ECD with reflected electrons requires only a short (∼500 μs) irradiation period followed by an appropriate delay for cooling and interaction. Reflection of the electron beam results in electrons trapped in or near the ICR cell and thus requires a brief (∼50 μs) purge for successful mass spectral acquisition. Further electron irradiation of refractory precursor ions did not result in further dissociation. Possibly the ion cloud and electron beam are misaligned radially, or the electron beam diameter may be smaller than that of the ion cloud such that remaining precursor ions do not overlap with the electron beam. Several ion manipulation techniques and use of a large, movable dispenser cathode reduce the possibility that misalignment of the ion and electron beams limits ECD efficiency.     

Detection of organic products of polymer pyrolysis by thermogravimetry-supersonic jet-skimmer time-of-flight mass spectrometry (TG-Skimmer-SPI-TOFMS) using an electron beam pumped rare gas excimer VUV-light source (EBEL) for soft photo ionisation

A commercial thermogravimetry—supersonic jet-skimmer quadrupole mass spectrometer system (TG-Skimmer-QMS, Netzsch GmbH, Germany) was successfully converted for soft single photon ionisation time-of-flight mass spectrometric (SPI-TOFMS) detection of organic compounds. VUV light for SPI was generated by an electron beam pumped argon excimer light source (EBEL; E _photon = 9.8 eV). Furthermore, the versatility of the system was conserved, as high temperature TG and DSC measurements as well as electron ionisation mass spectrometry for the detection of inorganic compounds are still possible. The new system was tested with two polymers and a hydrocarbon mixture (diesel). It was demonstrated that aliphatic and aromatic organic compounds can be detected without fragmentation. Thus the system allows the recording of a readily interpretable organic signature of, e.g. thermal polymer decomposition. The thermal degradation of polystyrene shows a rich signature of the monomer, some oligomers and minor products of irregular cleavings of carbon chains. Polycarbonate exhibits a thermal decomposition fingerprint which is dominated by products of bisphenol A. The bisphenol A monomer, however, is also detectable.     

Effect of vinyl acetate content and electron beam irradiation on the flame retardancy, mechanical and thermal properties of intumescent flame retardant ethylene-vinyl acetate copolymer

Ethylene vinyl acetate copolymer (EVA) flame retarded by ammonium polyphosphate (APP) and pentaerythritol (PER) was cross-linked by electron beam irradiation. The effects of vinyl acetate content and electron beam irradiation on the flame retardancy, mechanical and thermal properties of EVA composites were investigated. The volatilized products of EVA/APP/PER composites were characterized by thermogravimetric analysis/infrared spectrometry. As VA content increased, the volatilized products increased in the second decomposition step, but decreased in the third decomposition step. For all samples, the increase of irradiation dose could improve both the gel content and the Limit Oxygen Index (LOI, the minimum oxygen concentration by volume for maintaining the burning of a material) values of irradiated composites. The mechanical and thermal properties of the irradiated EVA composites were also evidently improved at appropriate irradiation dose as compared with those of unirradiated EVA composites, whereas these properties decrease at higher irradiation dose because of the electron beam irradiation-induced oxidative degradation or chain scission.     

Studies on the Thermal Decomposition of Benzoic Acid and its Derivatives

The thermal decomposition of benzoic acid and its derivatives containing —OH, —NH₂, —COOH and —SO₃H functional groups as substituents in ortho, meta and (or) para position together with sulphanilic acid was investigated. The analyses were performed using derivatograph, sample mass ranged from 50 to 200 mg, heating rates from 3 to 15 K min⁻¹ and static air atmosphere. It has been established that thermal decomposition of these aromatic acids proceeds through three common stages. In the first stage the phase transformations occur. The following two stages are due to the formation of intermediate products of the thermal decomposition and their combustion. Principal component analysis (PCA) was applied for evaluation of the results. Thanks to this method the influence of specific functional groups and their positions on the benzene ring on the thermal decomposition of the compounds under investigation was determined. This revised version was published online in July 2006 with corrections to the Cover Date.     

DSC and spectroscopic studies of disulfiram radiostability in the solid state

The effect of ionising radiation on the physico-chemical properties of disulfiram (Antabuse, Esperal, bisdiethylthiocarbamoil disulphide) has been studied by DSC, FTIR, EPR, MS, TLC and HPLC. Sterilisation was carried out in the solid state, at room temperature and normal air humidity using the electron beam of 9.96 Mev from accelerator. All the measurements were made simultaneously for the irradiated and nonirradiated substance. It has been found that the drug studied in solid phase when subjected to an electron beam corresponding to the irradiation in the doses 10–100 kGy shows the presence of free radicals (EPR), and a change in colour from white to pale green-grey that disappears after solution in water or methanol. After the irradiation with the dose of 100 kGy, its melting point and enthalpy slightly decreased. Also the content of the active substance decreases (HPLC −1.5%, UV −3.6%, iodometric titration method −2.7%) and trace amounts of the radiolysis products appear (HPLC). The substance irradiated with the doses 10–50 kGy does not show changes in the melting point, in the content and presence of the radiolysis products. The EPR results have shown that free radicals disappear after about a year and the discolouring disappears with them. The results of this study have shown that disulfiram can be subjected to sterilisation by irradiation with no deterioration of its physico-chemical properties, but a long time of storage needed to remove free radicals and discolouration questions the economic justification for this type of sterilisation.     

Electron beam accelerators—trends in radiation processing technology for industrial and environmental applications in Latin America and the Caribbean

The radiation processing technology for industrial and environmental applications has been developed and used worldwide. In Latin America and the Caribbean and particularly in Brazil there are 24 and 16 industrial electron beam accelerators (EBA) respectively with energy from 200 keV to 10 MeV, operating in private companies and governmental institutions to enhance the physical and chemical properties of materials. However, there are more than 1500 high-current electron beam accelerators in commercial use throughout the world. The major needs and end-use markets for these electron beam (EB) units are R and D, wire and electric cables, heat shrinkable tubes and films, PE foams, tires, components, semiconductors and multilayer packaging films. Nowadays, the emerging opportunities in Latin America and the Caribbean are paints, adhesives and coatings cure in order to eliminate VOCs and for less energy use than thermal process; disinfestations of seeds; and films and multilayer packaging irradiation. For low-energy EBA (from 150 keV to 300 keV). For mid-energy EBA (from 300 keV to 5 MeV), they are flue gas treatment (SO₂ and NO_X removal); composite and nanocomposite materials; biodegradable composites based on biorenewable resources; human tissue sterilization; carbon and silicon carbide fibers irradiation; irradiated grafting ion-exchange membranes for fuel cells application; electrocatalysts nanoparticles production; and natural polymers irradiation and biodegradable blends production. For high-energy EBA (from 5 MeV to 10 MeV), they are sterilization of medical, pharmaceutical and biological products; gemstone enhancement; treatment of industrial and domestic effluents and sludge; preservation and disinfestations of foods and agricultural products; soil disinfestations; lignocellulosic material irradiation as a pretreatment to produce ethanol biofuel; decontamination of pesticide packing; solid residues remediation; organic compounds removal from wastewater; and treatment of effluent from petroleum production units and liquid irradiation process to treat vessel water ballast. On the other hand, there is a growing need of mobile EB facilities for different applications in South America.     

Application of beam irradiation in preparation of visible light responsive TiO2 films

TiO₂ films were prepared by sol-gel method. In order to improve the utilization of light, the technologies of implantation of transition metal ions (V⁺ and Cr⁺) and electron beam irradiation to deposit noble metal particles (Ag and Pt) were used. A red shift was found in the spectrum of modified TiO₂ films. The photocatalytic experiments showed that the photocatalytic ability under visible light irradiation could be improved dramatically by both the implantation of transition metal and the electron beam irradiation. __________ Translated from Chinese Journal of Catalysis, 2007, 28(1): 39–44 [译自: 催化学报]     

Hidden rearrangement processes in short-lived negative molecular ions

The study of resonant electron capture by nitrobenzene molecules showed that some fragmentary negative ions are unstable toward electron autodetachment. The measured appearance energy of the neutral component of an [M — H]⁻ ion beam does not agree with the energetics of direct dissociation in a molecular ion. The estimation calculations show that the low appearance energy of [M — H]⁰ neutral components is caused by isomerization of a molecular ion of nitrobenzene to the 2-nitrobenzene structure followed by the formation of a phenoxide ion in the autodetachment state. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 367–370, February, 2006.     

Hydrothermal ageing of radiation cured epoxy resin-polyether sulfone blends as matrices for structural composites

The hydrothermal ageing of epoxy-thermoplastic blends, used as matrices for carbon fibre composites, cured by electron beam, has been studied. Two different thermoplastic percentages have been adopted. A suitable choice of both curing process and formulation parameters allows to carry out irradiation at mild temperature with several advantages, coming from a “non thermal” process, for both the final properties of the materials and the environment. Nevertheless the occurring of vitrification phenomena needs the use of a short thermal treatment after irradiation on the already solid materials, in order to complete the cure reactions. Radiation cured epoxy based matrices have been subjected to a thermal and moisture absorption ageing treatment and its influence on the thermal and mechanical properties has been investigated through dynamic mechanical thermal analysis and fracture toughness tests. The results have been interpreted on the basis of the different curing degree reached by the investigated systems and in the light of their morphological structures. Plasticization, thermal curing and degradation reactions occur in different extent depending on the kind of the material. In particular, for fracture properties, a better resistance to ageing is shown by the system at higher thermoplastic concentration.     

Enhanced performance as a lithium-ion battery cathode of electrodeposited V2O5 thin films by e-beam irradiation

The influence of electron beam irradiation on the electrochemical properties of electrodeposited V₂O₅ thin films was investigated. V₂O₅ thin films were deposited electrochemically onto indium tin oxide-coated glass from an aqueous vanadyl sulfate hydrate (VOSO₄⋅nH₂O) solution using Pt and Ag/AgCl as the counter electrode and reference electrode, respectively. Electrodeposition was performed potentiostatically at 1.7 V vs. Ag/AgCl. Electrodeposited samples were then subjected to a 1-MeV electron beam using an electron beam accelerator at the Korea Atomic Energy Research Institute. For comparison, a control sample was not irradiated with the electron beam. Crystallinity change before and after electron beam irradiation was investigated by X-ray diffraction and the oxidation state of vanadium determined by X-ray photoelectron spectroscopy. Scanning electron microscopy was utilized to examine surface morphology. It was observed that electron beam irradiation altered the oxidation state of vanadium and increased crystallinity. Significant morphological changes of V₂O₅ thin films were also observed with electron beam irradiation. Cyclic voltammetry was employed to evaluate the electrochemical properties of the synthesized V₂O₅ films in terms of their application as electrodes of lithium-ion battery. Compared with the control sample, which was not irradiated with an electron beam, the electron beam-irradiated V₂O₅ specimens showed much higher capacitance.     

Thermal analysis/mass spectrometry using soft photo-ionisation for the investigation of biomass and mineral oils

The combined analytical methods of thermal analysis and mass spectrometry have been applied in form of a newly developed prototype of a thermogravimetry — single photon ionisation time-of-flight mass spectrometer coupling (TG-SPI-TOFMS) to investigate the molecular patterns of evolved gases from several biomass samples as well as a crude oil sample. Single photon ionization (SPI) was conducted by means of a novel electron beam pumped argon excimer lamp (EBEL) as photon source. With SPI-TOFMS various lignin decomposition products such as guaiacol, syringol and coniferyl alcohol could be monitored. Furthermore, SPI allows the detection of aliphatic hydrocarbons, mainly alkenes, carbonylic compounds such as acetone, and furan derivatives such as furfuryl alcohol and hydroxymethylfurfural. More alkaline biomass such as coarse colza meal show intense signals from nitrogen containing substances such as (iso-)propylamine and pyrrole. Thermal degradation of crude oil takes place in two steps, evaporation of volatile components and pyrolysis of larger molecular structures at higher temperatures. Due to the soft ionisation, homologue rows of alkanes and alkenes could be detected on basis of their molecular ions. The obtained information from the thermal analysis/photo ionisation mass spectrometry experiments can be drawn on in comparison to the investigation of the primary products from flash pyrolysis of biomass for production of biofuels and chemicals.     

Radiation synthesis of silver nanostructures in cotton matrix

Cotton is one of the most popular natural fibres, composed mainly of cellulose, which finds a wide range of applications in paper, textile and health care products industry. Researchers have focused their interest on the synthesis of cotton nanocomposites, which enhances its mechanical, thermal and antimicrobial properties by the incorporation of various nanoparticles into the cotton matrix. Silver is one of the most popular antimicrobial agents with a wide spectrum of antibacterial and antifungal activity that results from a complex mechanism of its interactions with the cells of harmful microorganism. In this work, electron beam radiation was applied to synthesise silver nanostructures in cotton fibres. Investigations of the influence of the initial silver salt concentration on the size and distribution of the obtained silver nanostructures were carried out. A detailed characterisation of these nanocomposites with SEM-BSE and EDS methods was performed. TGA and DSC analyses were performed to assess the influence of different size silver nanoparticles and the effect of electron beam irradiation on the thermal properties of cotton fibres. A microbiological investigation to determine the antibacterial activity of Ag-cotton nanocomposites was carried out.     

Effect of crosslink density on some properties of electron beam-irradiated styrene–butadiene rubber

Crosslink densities of electron beam (EB)-irradiated styrene–butadiene rubber (SBR) samples were measured by using a novel magnetic resonance crosslink density spectrometer (MRCDS). With 1,1,1-trimethylolpropane triacrylate (TMPTA) loading increasing, the crosslink density of EB-irradiated SBR increases up to a certain level, and then decreases in the irradiation dose range 50–200 kGy. Tensile strength, elongation at break, thermal stability and pyrolysis products of the EB-irradiated SBR samples with different crosslink densities were also studied in this paper.     

Reinforcement of natural rubber/high density polyethylene blends with electron beam irradiated liquid natural rubber-coated rice husk

Coating of rice husk (RH) surface with liquid natural rubber (LNR) and exposure to electron beam irradiation in air were studied. FTIR analysis on the LNR-coated RH (RHR) exposed to electron beam (EB) showed a decrease in the double bonds and an increase in hydroxyl and hydrogen bonded carbonyl groups arising from the chemical interaction between the active groups on RH surface with LNR. The scanning electron micrograph showed that the LNR formed a coating on the RH particles which transformed to a fine and clear fibrous layer at 20 kGy irradiation. The LNR film appeared as patches at 50 kGy irradiation due to degradation of rubber. Composites of natural rubber (NR)/high density polyethylene (HDPE)/RHR showed an optimum at 20–30 kGy dosage with the maximum stress, tensile modulus and impact strength of 6.5, 79 and 13.2 kJ/m², respectively. The interfacial interaction between the modified RH and TPNR matrix had improved on exposure of RHR to e-beam at 20–30 kGy dosage.     

Variation of mechanical and thermal properties of the thermoplastics reinforced with natural fibers by electron beam processing

With restrictions for environmental protection being strengthened, the thermoplastics reinforced with natural fibers (NFs) such as jute, kenaf, flax, etc., appeared as an automobile interior material instead of the chemical plastics. Regardless of many advantages, one shortcoming is the deformation after being formed in high temperature of about 200 °C, caused by the poor adhesion between the natural fibers and thermoplastics. Also, the energy saving in connection with car air-conditioning becomes very important. In this study, the thermal conductivity, tensile strength, and deformation of several kinds of thermoplastic composites composing of 50% polypropylene (PP) and 50% natural fiber irradiated by the electron beam (energy: 0.5 MeV, dose: 0–20 kGy) were measured. The length and thickness of PP and NF are 80±10 mm and 40–120 μm, respectively. The results show that the thermal conductivity and the tensile strength changed and became minimum when the dose of electron beam is 10 kGy, and the deformation after the thermal cycle were reduced by the electron beam.     

Radioactive labeling in the study of abrasion of hard tooth tissue

Labeling the surface of hard tooth tissue samples by the nuclear recoil effect in radioactive decay was applied to study abrasion caused by abrasive components of tooth-pastes.²²²Rn and its short-lived decay products were implanted into the surface in vacuum. For this purpose irradiation was applied to sample placed very close to thin²²⁶Ra source. Measuring the activity before and after abrasion was used to evaluate abrasion in the system toothbrush — various suspensions of the tooth-pastes — hard tooth tissue (enamel or dentine) in a specially designed device, dentoabrasionmeter VUS 2.     

Electron beam irradiations of polypropylene syringe barrels and the resulting physical and chemical property changes

Mechanical, thermal, chemical decomposition and electron spin resonance (ESR) methods were used to study electron beam irradiated polypropylene syringe barrels that were irradiated to a total fractionated dose of 0, 20, 40, 60, and 80 kGy (in steps of 20 kGy). Dose mapping was conducted to determine dose to and through the syringe barrel. Analysis of these data indicated that degradation of the polypropylene syringes increased with an increase in electron beam irradiation.     

Polyethylene foams cross-linked by electron beam

Cross-linking of low-density polyethylene by electron beam irradiation was studied in this work with the aim of foam production by thermal expansion. Mechanical and thermal properties of the obtained foams were studied and it was found that relatively low doses up to 40 kGy could be used leading to a product with excellent surface appearance.     

电子束辐照与电化学还原联用技术——一种用于煤炭直接液化的新方法

对电子束辐照与电化学联用技术提高煤炭液化率的新型方法进行了研究。利用高能电子束对煤炭样品进行辐照,并通过四氢呋喃萃取出辐照后的可能产物并计算其提取率。实验结果发现,提取产率随着辐照剂量的增加而增加,并得到在氧气气氛下25 kGy的最佳辐照条件。辐照的样品进一步在氢氧化钠电解液中电化学还原液化,并采用元素分析法、傅里叶红外光谱法、阴极极化曲线法、核磁共振法和计时电流法等来检测辐照对煤炭电化学还原的影响。