Characterization of a distributed plasma ionization source (DPIS) for ion mobility spectrometry and mass spectrometry

A recently developed atmospheric pressure ionization source, a distributed plasma ionization source (DPIS), was characterized and compared to commonly used atmospheric pressure ionization sources with both mass spectrometry (MS) and ion mobility spectrometry (IMS). The source consisted of two electrodes of different sizes separated by a thin dielectric. Application of a high RF voltage across the electrodes generated plasma in air yielding both positive and negative ions. These reactant ions subsequently ionized the analyte vapors. The reactant ions generated were similar to those created in a conventional point-to-plane corona discharge ion source. The positive reactant ions generated by the source were mass identified as being solvated protons of general formula (H₂O)_nH⁺ with (H₂O)₂H⁺ as the most abundant reactant ion. The negative reactant ions produced were mass identified primarily as CO₃⁻, NO₃⁻, NO₂⁻, O₃⁻ and O₂⁻ of various relative intensities. The predominant ion and relative ion ratios varied depending upon source construction and supporting gas flow rates. A few compounds including drugs, explosives and amines were selected to evaluate the new ionization source. The source was operated continuously for 3 months and although surface deterioration was observed visually, the source continued to produce ions at a rate similar that of the initial conditions.     

聚醚醚酮酮和含联苯聚醚醚酮酮共聚物的熔融热

根据Ｆｌｏｒｙ热力学统计理论和比容－熔融热作国法，由ＤＳＣ结果得到了不同联苯含量的聚醚醚酮酮－含联苯聚醚醚酮酮（ＰＥＥＫＫ－ＰＥＢＥＫＫ）共聚物的熔融热，两种方法获得的结果吻合。在此基础上给出了ＰＥＥＫＫ－ＰＥＢＥＫＫ共聚物不同联苯含量的熔点计算表达式。结果还表明，随着联苯含量ｎＢ，的变化，明显改变；当ｎＢ＝０．３５时，ＰＥＥＫＫＰＥＢＥＫＫ共聚物的值最小。     

Morphology control of sulfonated poly(ether ketone ketone) poly(ether imide) blends and their use in proton-exchange membranes

Polymer blends based on sulfonated poly(ether ketone ketone) (SPEKK) as the proton-conducting component and poly(ether imide) (PEI) as the second component were considered for proton-exchange membranes (PEMs). The PEI was added to improve the mechanical stability and lower the water swelling in the fuel cell environment. Membranes were cast from solution using N-methyl-2-pyrrolidone (NMP) and dimethylacetamide (DMAc). The ternary, polymer/polymer/solvent, phase diagram was determined to provide guidance on how to control the morphology during solvent casting of blend membranes.

For blends of SPEKK (ion-exchange capacity = 2 mequiv/g) with PEI as the minority component, the morphology consisted of dispersed particles of 0.5–6 μm. Larger particles were achieved by increasing the PEI content and/or lowering the casting temperature. High-temperature annealing after solution casting did not affect the morphology of blend membranes, due to the low mobility and compatibility of the two polymers.

The possible use of SPEKK/PEI blends in PEMs is discussed in terms of existing theories of ion transport in polymers.     

Synthesis and characterization of trimethoxysilyl-functionalized poly(phthalazinone ether ketone)

A novel alkoxysilyl-functionalized poly(phthalazinone ether ketone)(PPEK)was prepared for the boundary lubricant application in micro-electro-mechanical system(MEMS).The synthesis of functionalized PPEK was started from the hydro- xylation of PPEK,then following with the corresponding ring-opening reaction of 3-glycidoxypropyltrimethoxysilane(GPTMS). The structures of the functional PPEK were confirmed by FTIR,~1H NMR,~(29)Si NMR,and UV-vis spectrum.     

Gas chromatography coupled to atmospheric pressure ionization mass spectrometry (GC-API-MS): Review

Although the coupling of GC/MS with atmospheric pressure ionization (API) has been reported in 1970s, the interest in coupling GC with atmospheric pressure ion source was expanded in the last decade. The demand of a “soft” ion source for preserving highly diagnostic molecular ion is desirable, as compared to the “hard” ionization technique such as electron ionization (EI) in traditional GC/MS, which fragments the molecule in an extensive way. These API sources include atmospheric pressure chemical ionization (APCI), atmospheric pressure photoionization (APPI), atmospheric pressure laser ionization (APLI), electrospray ionization (ESI) and low temperature plasma (LTP). This review discusses the advantages and drawbacks of this analytical platform. After an introduction in atmospheric pressure ionization the review gives an overview about the history and explains the mechanisms of various atmospheric pressure ionization techniques used in combination with GC such as APCI, APPI, APLI, ESI and LTP. Also new developments made in ion source geometry, ion source miniaturization and multipurpose ion source constructions are discussed and a comparison between GC-FID, GC-EI-MS and GC-API-MS shows the advantages and drawbacks of these techniques. The review ends with an overview of applications realized with GC-API-MS.     

Isothermal melt and cold crystallization kinetics of poly(aryl ether ketone ether ketone ketone)

The isothermal melt and cold crystallization kinetics of poly(aryl ether ketone ether ketone ketone) are investigated by differential scanning calorimetry over two temperature regions. The Avrami equation describes the primary stage of isothermal crystallization kinetics with the exponent n ≈ 2 for both melt and cold crystallization. With the Hoffman–Weeks method, the equilibrium melting point is estimated to be 406 °C. From the spherulitic growth equation proposed by Hoffman and Lauritzen, the nucleation parameter (K_g) of the isothermal melt and cold crystallization is estimated. In addition, the K_g value of the isothermal melt crystallization is compared to those of the other poly(aryl ether ketone)s. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1992–1997, 2000     

Radiochemical ageing of poly(ether ether ketone)

Thin (60 μm) and thick (250 μm) samples of poly(ether ether ketone) were subjected to radiochemical ageing at 24 kGy h⁻¹ dose rate for doses up to 30.7 MGy at 60 °C in air. FTIR spectrophotometry (hydroxyl and carbonyl build-up), ATR microscopy (oxidation profiles), ammonia gaseous treatment (determination of carbonyl nature), density, DSC (glass transition temperature, cold crystallization and melting point changes), and gel content measurements (crosslinking) were conducted for examination of polymer degradation. Thin samples were shown to undergo principally chain scission process whereas thick ones undergo mainly crosslinking. This difference can be attributed to the kinetic control of oxidation by oxygen diffusion. A mechanistic scheme was proposed from radiochemical yields estimations.     

Proton conductive membranes of sulfonated poly(ether ketone ketone)

Poly(ether ketone ketone) was sulfonated using fumic sulfuric acid and used for preparation of proton conductive membranes. The sulfonation degree was evaluated by elemental and thermal analysis and the IEC values were determined by titration. The proton conductivity of membranes with sulfonation degrees up to 70% was determined as a function of temperature by impedance spectroscopy. Membranes with sulfonation degree 38–70% were tested in DMFC experiments. Their performance was comparable to Nafion^® with the same pretreatment and clearly better than sulfonated poly(ether ether ketone) membranes with similar functionalization. The methanol crossover was lower than that of Nafion^® in the same conditions.     

Analysis of explosives using electrospray ionization/ion mobility spectrometry (ESI/IMS)

The analysis of explosives with ion mobility spectrometry (IMS) directly from aqueous solutions was shown for the first time using an electrospray ionization technique. The IMS was operated in the negative mode at 250°C and coupled with a quadrupole mass spectrometer to identify the observed IMS peaks. The IMS response characteristics of trinitrotoluene (TNT), 2,4-dinitrotoluene (2,4-DNT), 2-amino-4,6-dinitrotoluene (2-ADNT), 4-nitrotoluene (4-NT), trinitrobenzene (TNB), cyclo-1,3,5-trimethylene-2,4,6-trinitramine (RDX), cyclo-tetramethylene-tetranitramine (HMX), dinitro-ethyleneglycol (EGDN) and nitroglycerine (NG) were investigated. Several breakdown products, predominantly NO₂⁻ and NO₃⁻, were observed in the low-mass region. Nevertheless, all compounds with the exception of NG produced at least one ion related to the intact molecule and could therefore be selectively detected. For RDX and HMX the [M+Cl⁻]⁻ cluster ion was the main peak and the signal intensities could be greatly enhanced by the addition of small amounts of sodium chloride to the sprayed solutions. The reduced mobility constants (K₀) were in good agreement with literature data obtained from experiments where the explosives were introduced into the IMS from the vapor phase. The detection limits were in the range of 15–190 μg l⁻¹ and all calibration curves showed good linearity. A mixture of TNT, RDX and HMX was used to demonstrate the high separation potential of the IMS system. Baseline separation of the three compounds was attained within a total analysis time of 6.4 s.     

Evaluation of high-field asymmetric waveform ion mobility spectrometry mass spectrometry for the analysis of the mycotoxin zearalenone

A high-field asymmetric waveform ion mobility spectrometry (FAIMS)-based method for the determination of the mycotoxin zearalenone (ZON) and its metabolites α-zearalenol (α-ZOL), β-zearalenol (β-ZOL), and β-zearalanol (β-ZAL), in a cornmeal (maize) matrix is described. Detection limits achieved using the FAIMS device coupled with electrospray ionization (ESI) and mass spectrometric (MS) detection are 0.4 ng mL⁻¹ for ZON and 3 ng mL⁻¹ for α-ZOL + β-ZOL, and β-ZAL. This represents a significant improvement when compared to detection limits determined using ESI-MS or ESI-tandem mass spectrometry (MSMS) analytical methods. The developed flow-injection (FIA)-ESI-FAIMS-MS method was applied to reference materials ERM-BC-716 and ERM-BC-717 certified for ZON and excellent agreement with the certified values was observed.     

Evaluation of false positive responses by mass spectrometry and ion mobility spectrometry for the detection of trace explosives in complex samples

Secondary electrospray ionization-ion mobility-time of flight mass spectrometry (SESI-IM-TOFMS) was used to evaluate common household products and food ingredients for any mass or mobility responses that produced false positives for explosives. These products contained ingredients which shared the same mass and mobility drift time ranges as the analyte ions for common explosives. The results of this study showed that the vast array of compounds in these products can cause either mass or mobility false positive responses. This work also found that two ingredients caused either enhanced or reduced ionization of the target analytes. Another result showed that an IMS can provide real-time separation of ion species that impede accurate mass identifications due to overlapping isotope peak patterns. The final result of this study showed that, when mass and mobility values were used to identify an ion, no false responses were found for the target explosives. The wider implication of these results is that the possibility exists for even greater occurrences of false responses from complex mixtures found in common products. Neither IMS nor MS alone can provide 100% assurance from false responses. IMS, due to its low cost, ease of operation, rugged reliability, high sensitivity and tunable selectivity, will remain the field method of choice for the near future but, when combined with MS, can also reduce the false positive rate for explosive analyses.     

Glass transition and miscibility in blends of two semicrystalline polymers: Poly(aryl ether ketone) and poly(ether ether ketone)

Binary melt‐blended mixtures of two aryl ether ketone polymers (i.e., a new poly(aryl ether ketone) (code name PK99) and poly(ether ether ketone) (PEEK), have been studied. Polymer miscibility in glassy amorphous (or melt) domains has been demonstrated for the binary blend comprising of two aryl‐ether‐ketone‐type semicrystalline polymers. Composition‐dependent, single T_g was observed within full composition range in the PK99/PEEK blends, and the narrow T_g breadth also suggests that the scale of mixing was fine and uniform. To better resolve any possible overlapping T_g's, physical aging was imposed on a comparison set of blend samples for the purpose of improving detectability of overlapped multiple transitions if existing. The result still showed one single T_g. The relative sharp T_g and lack of cloud point transition suggest that the scale of molecular intermixing is good. Phase homogeneity was further confirmed using optical and scanning electron microscopy. The X‐ray diffractograms suggest that isomorphism does not exist in the PK99/PEEK blends and that the crystal forms of the respective polymers remain distinct and unchanged by the miscibility in the amorphous region. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1485–1494, 1999     

Towards metals analysis using corona discharge ionization ion mobility spectrometry

For the first time, the capability of corona discharge ionization ion mobility spectrometry (CD-IMS) in the determination of metal complex was evaluated. The extreme simplicity of dispersive liquid–liquid microextraction (DLLME) coupled to the high sensitivity of CD-IMS measurement could make this combination really useful for simple, rapid, and sensitive determination of metals in different samples. In this regard, mercury, as a model metal, was complexed with diethyldithiocarbamate (DEDTC), and then extracted into the carbon tetrachloride using DLLME. Some parameters affecting the extraction efficiency, including the type and volume of the extraction solvent, the type and volume of the disperser solvent, the concentration of the chelating agent, salt addition and, pH were exhaustively investigated. Under the optimized condition, the enrichment factor was obtained to be 142. The linear range of 0.035–10.0 μg mL⁻¹ with r² = 0.997 and the detection limit of 0.010 μg mL⁻¹ were obtained. The relative standard deviation values were calculated to be lower than 4% and 8% for intra-day and inter-day, respectively. Finally, the developed method was successfully applied for the extraction and determination of mercury in various real samples. The satisfactory results revealed the capability of the proposed method in trace analysis without tedious derivatization or hydride generation.     

Fluorenyl-containing sulfonated poly(aryl ether ether ketone ketone)s (SPFEEKK) for fuel cell applications

A series of fluorenyl-containing sulfonated poly(aryl ether ether ketone ketone)s (SPFEEKK) were synthesized via aromatic nucleophilic substitution polymerization. The sulfonation content (SC) was controlled by the feed ratios of sulfonated and nonsulfonated monomers. Flexible and strong membranes in the sulfonic acid form were obtained from cast membranes in the sodium salt forms by treatment with acid. The thermal properties, water uptake, swelling ratio, water state, oxidative stability, proton conductivity and methanol permeability were investigated. All the polymers had proton conductivities greater than 1 × 10⁻² S/cm at room temperature, and the conductivity values of m-SPFEEKK-80 and p-SPFEEKK-80 were up to 1.86 × 10⁻¹ and 1.78 × 10⁻¹ S/cm at 100 °C. This series of polymers also possessed good dimensional stability in water and low methanol crossover.     

Dynamic relaxation behavior of solvent-crystallized poly(ether ether ketone)

The dynamic relaxation behavior of solvent-crystallized poly(ether ether ketone) (PEEK) has been investigated in the region of the glass-rubber (α) relaxation using dynamic mechanical and dielectric methods. Amorphous PEEK films were exposed to saturated methylene chloride and acetone vapor, with solvent-induced crystallization observed for both penetrants. Sample desorption at elevated temperatures (under vacuum) resulted in virtually complete removal of residual penetrant, thus providing for the measurement of relaxation characteristics independent of plasticization. Both dynamic mechanical and dielectric studies indicated a marked positive offset in the isochronal relaxation temperatures of the solvent-crystallized samples relative to thermally crystallized specimens of comparable bulk crystallinity, and a higher apparent activation energy in the solvent-crystallized case. These results are consistent with the evolution of a tighter crystalline morphology (i.e., smaller crystal long spacing) in the solvent-crystallized samples, the crystallites imposing a greater degree of constraint on the long-range motions of the amorphous chains inherent to the glass-rubber relaxation. © 1994 John Wiley & Sons, Inc.     

Novel fluorinated poly(aryl ether ketone)s

Two novel fluorinated monomers were prepared and polymerized with biphenols to produce amorphous, thermally stable poly(aryl ether ketone)s. The properties of the fluorinated polymers are compared to those of unfluorinated, amorphous poly(aryl ether ketone)s. The presence of fluorine in the polymers was found to cause a decrease in glass transition temperature and Young's moduli, however, no increase in thermal stability was observed. The fluorinated polymers are soluble in common organic solvents such as chloroform and methylene chloride at room temperature, and also show solubility in solvents containing a ketonic moiety, such as acetone. Evidence of polymer branching through fluorines considered to be unreactive under the polymerization conditions was found. Efforts were made to evaluate the reactivity of fluorine atoms under the polymerization conditions using both molecular modeling and ¹⁹F-NMR to ascertain if such branching could be avoided. © 1995 John Wiley & Sons, Inc.     

Synthesis and characterization of aromatic poly(ether ketone)s containing cyclotriphosphazene units

Bis(4-oxybenzoic acid) tetrakis(phenoxy) cyclotriphosphazene (IUPAC name: 4-[4-(carboxyphenoxy)-2,4,6,6-tetraphenoxy-1,3,5,2λ⁵,4λ⁵,6λ⁵-triazatriphosphinin-2-yl]oxy-benzoic acid) was synthesized and direct polycondensed with diphenylether or 1,4-diphenoxybenzene in Eaton's reagent at the temperature range of 80–120°C for 3 hours to give aromatic poly(ether ketone)s. Polycondensations at 120°C gave polymer of high molecular weight. Incorporation of cyclotriphosphazene groups in the aromatic poly(ether ketone) backbone greatly enhanced the solubility of these polymers in common organic polar solvents. Thermal stabilities by TGA for two polymer samples of polymer series ranged from 390 to 354°C in nitrogen at 10% weight loss and glass transition temperatures (T_g) ranged from 81.4 to 89.6°C by DSC. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1227–1232, 1998     

Radiation degradation of poly(arylene ether ketone)s

The resistance of five poly(arylene ether ketone)s with related chemical structures to degradation by ionizing radiation has been studied by ESR spectroscopy and yields of volatile products. All of the polymers showed high resistance to radiation with low yields of radicals after irradiation in vacuum at 77 K (when up to 84% of the radicals were identified as radical anions) and much lower yields at 300 K. The yields of volatile products were much less than reported for poly(arylene sulfone)s [1, 2]. Methyl substitution on a main-chain aromatic ring decreased the radiation resistance, but methane only comprised 10% of the volatile products from the methyl-substituted polymers. A polymer containing an isopropylidene group in the main chain and a substituent aromatic carbonyl showed significantly decreased radiation resistance. Extremely low radical yields were obtained after irradiation in air at 300 K, contrary to many polymers. XPS analysis showed an increase in C–O bonds on the surface after irradiation in air.     

Coupling of solid phase microextraction with electrospray ionization ion mobility spectrometry and direct analysis of venlafaxine in human urine and plasma

The capability of electrospray ionization-conventional ion mobility spectrometry (ESI–IMS) for direct analysis of the samples extracted by solid phase microextraction (SPME) was investigated and evaluated for the first time. To that end, an appropriate new desorption chamber was designed and constructed, resulting in the possibility of direct exposure of the SPME fiber to the electrospray solvent flow. Two different elution methods in dynamic and static modes were exhaustively investigated. The results indicated that the interface could help us to have an accurate and sensitive analysis without disturbing the electrospray process, in static elution method. Venlafaxine as a test compound was extracted from human urine and plasma by a convenient headspace SPME method. The positive ion mobility spectrum of the extracted drug was obtained and the analyte responses were calculated. The coupled method of SPME–ESI–IMS was comprehensively validated in terms of sensitivity, dynamic range, and recovery percentage. Finally, various real samples of human urine and plasma were analyzed, all verifying the feasibility and success of the proposed method for the easy routine analysis.     

Determination of polymer additives by liquid chromatography coupled with mass spectrometry. A comparison of atmospheric pressure photoionization (APPI), atmospheric pressure chemical ionization (APCI), and electrospray ionization (ESI)

A method for the determination of polymer additives like antioxidants, UV absorbers and processing stabilizers using liquid chromatography (LC) coupled with atmospheric pressure photoionization mass spectrometry (APPI-MS) is presented. Ion source parameters were optimized regarding temperatures, gas flow rates, and voltages applied. Detection limits were determined using APPI with or without dopant and were compared with electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI). Differences between APPI, ESI and APCI are pointed out and the effect of the dopant toluene and acetone is discussed. The optimized method yielded detection limits between 0.001 mg L⁻¹ and 0.022 mg L⁻¹ for 15 different analytes. Linear calibration plots could be obtained for all solutes over a wide concentration range showing satisfying repeatability with standard deviations of peak areas between 3.4% and 7.6%. The results indicate that the developed method can be regarded as suitable for the quantitative determination of polymer additives even at low concentration levels.