Rapid characterization of polyalcohols by silylation and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

A matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry method for rapidly enumerating hydroxyl groups in analytes is described, and applied to some common polyalcohols (erythritol, mannitol and xylitol). Polyalcohols were derivatized with trimethylsilylimidazole (TMSI) either separately or as mixtures, and were analyzed, without chromatographic separation or purification. The mass spectra revealed consecutive peaks that are separated by 72 m/z units as a consequence of displacement of one hydroxyl hydrogen atom by one TMS group. The number of observed peaks was used to confirm the number of hydroxyl groups in each analyte.     

Rapid characterization of edible oils by direct matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis using triacylglycerols

Direct matrix-assisted laser desorption/ionization time-of-flight mass spectrometric (MALDI-TOFMS) analysis of solutions of edible fats/oils yielded spectra useful for their rapid differentiation and classification. Results also reflected the individual fatty acid components and their degree of unsaturation. After dissolution in hexane, MALDI-MS analysis revealed spectra showing characteristic triacylglycerols (TAGs), the main fat/oil components, as sodium adduct ions. The Euclidean distances calculated using the mass and intensity values for 20 TAGs were used to evaluate and compare spectra. With cluster analysis, animal fats grouped together differently than vegetable oils and the individual oils grouped together by type. The ion abundances for the individual TAGs and their presumed compositions were used to approximate the overall fatty acid composition of canola, soybean, corn, olive and peanut oil, as well as lard. Using this approach the calculated fatty acid compositions and degree of unsaturation generally fell within about 4% of literature values. When the degree of saturation was compared with values calculated from the package labeling the differences were about 7%.     

Evolution of bioceramics within the field of biomaterials

This review article, dedicated to Prof. Jacques Livage, is focused on current trends in bioceramics. The first generation of inert ceramics aimed to substitute natural bone, hence the research was only focused on inert materials; the second one was aimed at mimicking some biomineralization-related functions and sol-gel chemistry plays a paramount role in their synthesis and properties. Finally, the purpose with third generation bioceramics is basically to provide an adequate scaffolding system which helps the bone cells to perform their natural processes. Tissue engineering attempts to develop artificial materials able to replace biological tissues in situations where the human body cannot perform said replacement by itself. One attempt consists on designing biomimetic materials that combine synthetic materials with cellular recognizing positions. These ceramics must exhibit an adequate degree of porosity. All these ideas shall be discussed in the present work.     

Coal characterization by on-line pyrolysis-field ionization mass spectrometry

Summary Pyrolysis-field ionization mass spectrometry (Py-FIMS) was used for the first time to directly characterize Chinese coals and their extracts. The summed mass spectra (about 30 magnetic scans) of four coal samples and the dimethylformamide extracts of two very different coals were registered between 50° and 750°C using linear heating in high vacuum (10^–3 Pa) and approximately 6 min temperature rise time. Utilizing temperature-programmed pyrolysis and FI as soft ionization mode, the spectra displayed almost exclusively molecular ions of the evolved products. The thermograms, i.e. the intensities of the total ion current and selected ions were plotted versus the scan number, heating time and temperature. In general, two maxima in these thermograms were observed, which were different for the coals and reflected their carbon/hydrogen content. Comparing the mass spectra of the low temperature part (first maximum) with summed spectra of the extracts shows an interesting similarity. In contrast, the high temperature part (second maximum) indicates the products of thermo-degradation. The applied method is a fast and convenient tool for the characterization of evolved volatiles and thermal degradation products of coals and coal extracts.

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Kennzeichnung von Kohlen mit direkter Pyrolyse und Feldionisations-Massenspektrometrie

     

Rapid characterization of protein productivity and production stability of CHO cells by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

The biopharmaceutical industry has been in pursuit of strategies which can isolate stable and high-producing cell lines. The whole cell mass spectrometry method by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) is a rapid and simple method for cell characterization based on the differences in the fingerprints of the mass spectra. This work describes how the method was evaluated for the application of screening for stable and high-producing clones from a panel of recombinant Chinese hamster ovary (CHO) cell lines. Detectable m/z values and their relative intensities were collected and processed by partial least squares (PLS). To reduce the errors introduced by the preparation method and spectra noise, high intensity preliminary data was selected and the number of variables introduced was validated by leave-one-out cross-validation. The differences in recombinant protein productivity and titer were revealed by PLS regression with promising results. Partial least-squares discriminant analysis (PLS-DA) was applied to differentiate stable and unstable cell lines as traditional stability testing would require several months involving numerous continuous passages. Results confirmed that the whole cell MALDI-TOF method can be a powerful method for routine monitoring of bioprocesses and study can be further developed by extending the number of the cell lines tested to establish a recombinant cell line database.     

Ionization and dissociation of diethylamine by field ionization mass spectrometry

The field ionization mass spectrum of diethylamine on a 5 μm activated wire at 300 K yields surface product ions like protonated molecular ions and doubly charged ions as well as gas phase ions like parent minus CH₃ group. Variations of the reaction rate as a function of the decomposition times in the range 10^?11-10^?6 s for the elimination of a CH₃ group are studied. The reaction rates are evaluated with the help of the retarding potential technique.     

Thermal degradation of aliphatic polyamides studied by field ionization and field desorption mass spectrometry

The aliphatic polyamides nylon 6.6, 6.9, 6.10, 6.12, 12.6, 12.10, and 12.12 of the diamine dicarboxylic acid-type were pyrolyzed in the ion source of a double-focusing mass spectrometer and the thermal degradation products were recorded by field ionization (FI) and field desorption (FD) mass spectrometry (MS). In the FI mode, several series of thermal degradation products differing in the number of polymer repeating units were detected up to 1000 Daltons. The main products were oligomers and, in addition, protonated dinitriles and various protonated nitriles are formed in large amounts except for nylon 6.6 and nylon 12.6. These two polymers form, in contrast to all other samples, large amounts of protonated amides and diamines. The technique employed allows distinction between oligomers already present in the original polymer and oligomers formed by thermal fission of bonds in the polymer chain. Reaction mechanisms are given that explain the products observed. High resolution experiments and accurate mass measurements were performed to confirm the proposed structures. In the FD mode, cationized oligomers (attached mostly to a sodium cation) were observed below 200°C with the dimers being the base peak for most samples. In contrast to the FI results, the monomers were only detected at very low intensities. Similarly, only weak signals for additional thermal degradation products were registered except for nylon 12.6. At higher temperatures the FD mass spectra gave protonated and doubly protonated oligomers in the high mass range up to 2000 Daltons, which resulted in complementary structural information about the polymers.     

Migration effects in field ionization

A model is presented for processes at a field emitter in the quasistationary state, which incorporates this migration. It gives a qualitative explanation for how the ion current varies with field, temperature, and pressure.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 24, No. 4, pp. 434–439, July–August, 1988.     

Rapid authentication of Gastrodiae rhizoma by direct ionization mass spectrometry

In this study, direct ionization mass spectrometry (DI-MS) for rapid authentication of Gastrodiae rhizoma (known as Tianma in Chinese), a popular herbal medicine, has been developed. This method is rapid, simple and allows direct generation of characteristic mass spectra from the raw herbal medicines with the application of some solvents and a high voltage. The acquired DI-MS spectra showed that gastrodin, parishin B/parishin C and parishin, the major active components of Gastrodiae rhizoma, could be found only in genuine Gastrodiae rhizoma samples, but not in counterfeit samples, thus allowing rapid authentication of Gastrodiae rhizoma. Moreover, wild and cultivated Gastrodiae rhizoma could be classified and Gastrodiae rhizoma from different geographical locations could be differentiated based on their different intensity ratios of characteristic ions or principal component analysis (PCA). This method is simple, rapid, reproducible, and can be extended to analyze other herbal medicines.     

Secondary ionization of neutral products by field dissociation of molecular ions

An analysis of the data obtained herein and literature data on the field-ionization mass spectra of simple compounds has permitted advancement of the hypothesis that the free radicals formed upon cleavage of bonds in the molecular ions in a strong electric field undergo secondary field ionization when the following conditions are fulfilled: a) the ionization potentials of the neutral dissociation products do not exceed the ionization potentials of the original molecules; b) dissociation of the molecular ions occurs so rapidly that these ions and their decomposition products do not manage to leave the zone of the strong field during the dissociation process.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 22, No. 6, pp. 733–737, November–December, 1986.     

Rapid analysis of svoc in aerosols by desorption electrospray ionization mass spectrometry

Desorption electrospray ionization mass spectrometry (DESI-MS) was applied for the first time to the analysis of semivolatile organic compounds (SVOC) in atmospheric aerosols. We took polycyclic aromatic hydrocarbons (PAHs) as representatives of SVOCs. The DESI-MS conditions were optimized and the limit of detection for PAHs was about 10 pg with 5 s sampling time. PAHs from both laboratory-made biomass burning aerosols and ambient aerosols were selectively and rapidly analyzed without extraction or preconcentration. The observed PAH species and their relative ion intensities are discussed. This work demonstrates that DESI-MS is a promising method for rapid semiquantitative analysis of SVOC in atmospheric aerosols.     

Rapid determination of 5-hydroxymethylfurfural by DART ionization with time-of-flight mass spectrometry

DART (direct analysis in real time), a novel technique with wide potential for rapid screening analysis, coupled with high-resolution time-of-flight mass spectrometry (TOF-MS) has been used for quantitative analysis of 5-hydroxymethylfurfural (5-HMF), a typical temperature marker of food. The DART/TOF-MS method was optimised and validated. Quantification of 5-HMF was achieved by use of a stable isotope-labelled 5-HMF standard prepared from glucose. Formation of 5-HMF from saccharides, a potential source of overestimation of results, was evaluated. Forty-four real samples (honey and caramelised condensed sweetened milk) and 50 model samples of heated honey were analysed. The possibility of using DART for analysis of heated samples of honey was confirmed. HPLC and DART/TOF-MS methods for determination of 5-HMF were compared. The correlation equation between these methods was DART?=?1.0287HPLC?+?0.21340, R ²?=?0.9557. The DART/TOF-MS method has been proved to enable efficient and rapid determination of 5-HMF in a variety of food matrices, for example honey and caramel.     

Rapid screening and characterization of metabolites from a marine-derived actinomycete by high-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight mass spectrometry

A rapid and reliable method has been optimized and established for the analysis of the metabolites from a marine actinomycete by high‐performance liquid chromatography coupled with electrospray ionization quadrupole time‐of‐flight mass spectrometry (HPLC/QTOF MS/MS). From MS/MS spectra, the product ions of [M + H]⁺ were recorded to provide abundant structural information of the mother nucleus and peptide moieties. Using the QTOF MS/MS and in‐source collision‐induced dissociation (in‐source CID) techniques, three main metabolites including actinomycin D, actinomycin V and actinomycin I were determined and characterized by elemental compositions of precursor and product ions (<7 ppm). Additionally, this method provided information about the compositions of the peptide residues and the sequences of the amino acid from a series of fragment ions. It proved useful for the identi?cation of the metabolites in marine samples which have similar structures especially when there were no reference compounds available. Copyright © 2010 John Wiley & Sons, Ltd.     

Structural characterization of acetylpyridinium-ethyl pyruvate adducts by electrospray ionization mass spectrometry

The reactions of ethyl pyruvate with acetic anhydride and pyridine were studied by electrospray ionization mass spectrometry (ESI-MS). Ethyl 2-acetoxy-2-pyridiniumpropionate (1) (m/z 238) resulting from the reaction of the acetylpyridinium cation with ethyl pyruvate, and the adduct of ethyl 2-acetoxyacrylate with a pyridinium cation (2), bound together by non-covalent interactions (m/z 238), were identified by ESI-MS for the first time. Structures 1 and 2 cannot be distinguished, probably because one may be converted into the other and vice versa.     

Coal-tar pitch characterization by thin-layer chromatography with flame ionization detection

Summary A rapid and quantitative method for compound class characterization of coal-tar pitches without previous fractionation, using an improved TLC method with an FID system, has been developed. Results show adequate accuracy and precision, including the sampling step.A fast calibration method, based on a variation of the internal normalization procedure, can be used for up to 18 g of whole sample application, avoiding the usually tedious absolute calibration in such analyses. This range is more than sufficient in view of the small amounts usually spotted in this technique.Speed of sample application by autospotter influences the shape of the peak nearest the point of application. For the coal tar pitch studied (9 wt.% non-eluted), slow application (0.5 L min^–1) gives a non-eluted Gaussianintegratable peak. A faster speed (10 L min^–1) is usable for analysing fossil products with lower non-eluted content. Total analysis time is less than 2 h, a considerably improvement on current methods.     

Rapid classification of perfumes by extractive electrospray ionization mass spectrometry (EESI-MS)

Extractive electrospray ionization mass spectrometry (EESI-MS) was applied to rapid fingerprinting of various perfumes for quality classification. Unique EESI-MS fingerprints of ten famous brands were obtained. This technique was shown to be applicable to rapid forgery detection on the example of an authentic and a counterfeit 'Miss Dior' fragrance by Christian Dior. We believe that the high throughput and simplicity of this sample-preparation-free method can be advantageous in the perfume industry, for instance when applied to online quality control.     

Rapid gas-chromatographic determination of hydrocarbon types by selective absorption and flame ionization detection

A fast one-step technique has been developed for the resolution of hydrocarbons into aromatics, olefines and saturates. The analyser consists of three branches with different capillary restrictions, specific absorbers and delayers, and can be applied to gaseous or liquid samples of hydrocarbons with a boiling point of up to 220°C. The time required for an analysis under optimal conditions is 6 min. The analyser is installed directly in the oven of the gas chromatograph, using a single flame ionisation detector. It was tested by selected hydrocarbons occurring in gasoline in significant amounts in different concentration ranges. Leaded and unleaded commercial gasolines were examined as real samples. The method had been successfully applied to the fast identification of hydrocarbons in the case of fuel spills.     

热辅助解吸-介质阻挡放电离子化质谱快速检测磺胺类药物

磺胺类药物在家禽养殖行业中的滥用是一个极其严重的问题。该文采用一种热辅助解吸介质阻挡放电离子化质谱技术(HAD-DBDI-MS),通过对其加热温度等参数的优化,建立了对磺胺吡啶、磺胺间甲氧嘧啶、磺胺喹口恶啉、磺胺胍及磺胺甲口恶唑等磺胺类药物的快速检测方法,并通过二级质谱进行结构鉴定;与单独使用DBDI-MS相比,HAD-DBDI-MS的检出限降低了1～2个数量级。对鸡肉模拟加标进行了直接快速检测应用,实现了鸡肉中模拟添加磺胺吡啶的检出;通过在加热时引入甲醇辅助挥发,实现了对饲料模拟加标压片样品中磺胺胍、磺胺甲口恶唑的检出。结果表明,HAD-DBDI-MS为禽类肉制品和饲料中磺胺类药物的快速检测提供了一种新的方法。