Nicolas V. Schwab

Bacterial identification: from the agar plate to the mass spectrometer

For more than a century, bacteria and fungi have been identified by isolation in culture followed by enzymatic reactions and morphological analyses. The identification of environmental microorganisms, however, remains a challenge because biochemical and staining protocols for bacteria identification are tedious, usually stepwise, can be long (days) and are prone to errors. Molecular techniques based on DNA amplification and/or sequencing provide more secure molecular identification of specific bacteria, but identification based on mass spectrometry (MS), mainly on MALDI-MS, has been shown to be an alternative accurate and fast method able to identify unknown bacteria on the genus, species and even subspecies level based profiles of proteins and peptides derived from whole bacterial cells. Breakthroughs such as non-culture-based identification of bacteria from biological fluids and MS detection of antibiotic resistance have recently been reported. This review provides an overview of the traditional bacterial and fungal identification workflow and discusses the recent introduction of MS as a powerful tool for the identification of microorganisms. Principles and applications of MS, followed by the use of high-quality databases with dedicated algorithms, are discussed for routine microbial diagnostics, mainly in human clinical settings and in veterinary medicine.

Fingerprinting of sildenafil citrate and tadalafil tablets in pharmaceutical formulations via X-ray fluorescence (XRF) spectrometry.

The production of counterfeited drugs is a criminal problem that carries serious risks to public health in the worldwide. In Brazil, Viagra and Cialis are the most counterfeit medicines, being used to inhibit the phosphodiesterase type 5 (PDE-5), treating thus, problems related to erectile dysfunction. X-ray fluorescence (XRF) is a suitable technique to control the quality of new pharmaceutical formulations and distinguish between authentic and counterfeit tablets. XRF has advantageous features like multielemental capability, good detectivity, high precision, short analysis times, and is nondestructive, which makes it suitable to be extended to a great variety of samples. In this work, the inorganic fingerprinting chemical of forty-one commercial samples (Viagra, Cialis, Lazar, Libiden, Maxfil, Plenovit, Potent 75, Rigix, V-50, Vimax and Pramil) and fifty-six counterfeit samples (Viagra and Cialis) were obtained from XRF data. XRF presented an excellent analytical methodology for semi-quantitative determination of active ingredient (in case of sildenafil citrate that presents S in its structure) and excipients such as calcium phosphate, titanium oxide and iron oxide (P, Ca, Ti and Fe). The matrix data were allied to chemometric methods (Principal Component Analysis and Hierarchical Cluster Analysis) to classify the tablets investigated between authentic and counterfeit, grouping the samples into of seven groups: A, B, C, D and E (counterfeit group) and F and G (authentic group).

Standard methods for Apis mellifera propolis research

Propolis is one of the most fascinating honey bee (Apis mellifera L.) products. It is a plant derived product that bees produce from resins that they collect from different plant organs and with which they mix beeswax. Propolis is a building material and a protective agent in the bee hive. It also plays an important role in honey bee social immunity, and is widely used by humans as an ingredient of nutraceuticals, over-the-counter preparations and cosmetics. Its chemical composition varies by geographic location, climatic zone and local flora. The understanding of the chemical diversity of propolis is very important in propolis research. In this manuscript, we give an overview of the available methods for studying propolis in different aspects: propolis in the bee colony; chemical composition and plant sources of propolis; biological activity of propolis with respect to bees and humans; and approaches for standardization and quality control for the purposes of industrial application.

Intact triacylglycerol profiles of fats and meats via thermal imprinting easy ambient sonic-spray ionization mass spectrometry

Thermal imprinting (TI) on a paper surface, using minimal solvent amounts, followed by direct analysis of the triacylglycerols (TAG) content via easy ambient sonic-spray ionization mass spectrometry (EASI-MS) is shown to provide a fast protocol to analyze TAG in meats and fats. The technique is simple, fast and eco-friendly requiring no hydrolysis, derivatization or chromatographic separation. The entire TI-EASI-MS protocol is performed in a few minutes and with minimal sample handling and solvent consumption. The TAG profiles obtained via TI-EASI-MS are shown to be quite similar to those obtained using GC and MALDI-MS analyses, and the imprinting and mailing of the imprinted paper in a sealed plastic bag is proposed for remote TI-EASI-MS analysis of meat and fat samples.

High throughput MS techniques for caviar lipidomics

The lipid profile of Sturgeon roe (caviar) was monitored by matrix assisted laser desorption/ionization mass spectrometry (MALDI(+)-MS), thermal imprinting easy ambient sonic-spray ionization mass spectrometry (TI-EASI(+)-MS) and electrospray mass spectrometry (ESI(+)-MS). Freshly salted and commercially salted pasteurized caviar samples of Atlantic sturgeon (Acipenser sturio) were stored either at +4 °C or at room temperature for 4 weeks. The different types of chemical information achieved by these MS techniques were compared: MALDI(+)-MS detects mainly phospholipids (PL) whereas TI-EASI(+)-MS allows monitoring of both triacylglycerols (TAG) and PL. ESI(+) coupled to Fourier transform ion cyclotron resonance high resolution mass spectrometer (FT-ICR-MS) and MS/MS experiments were used to fully characterize the detected lipids, ensure the absence of oxidation products in the degradation process and confirm the high efficiency of the thermal imprinting extraction. TI-EASI(+)-MS, via a more comprehensive profiling and easier operation, has therefore been demonstrated to provide caviar lipidomic profiles and discriminate its changes as a function of storage time and temperature. The data have also confirmed that hydrolysis is the main process of lipid degradation in caviar.

Ambient mass spectrometry employed for direct analysis of intact arabica coffee beans

As tecnicas de ionizacao ambiente na espectrometria de massas: ionizacao de dessorcao por eletrospray (DESI) e ionizacao ambiente por spray sonico (EASI) foram exploradas como uma forma simples e rapida para analisar diretamente a superficie intacta de graos de cafe arabica tratados pelas vias seca, semi-seca e umida. Cinco substâncias foram identificadas, incluindo tres componentes da camada de cera que recobre os graos verdes de cafe (βN-araquidonoil-5-hidroxitriptamida, βN-behenoil-5-hidroxitriptamida e βN-lignoceroil-5-hidroxitriptamida) e geralmente associadas com irritacoes estomacais que a bebida do cafe provoca em individuos sensiveis. Alem disso, os processos de pos-colheita empregados nos cafes puderam ser diferenciados atraves da ferramenta estatistica multivariada analise de componentes principais (PCA) usando dados de perfil quimico das amostras. Nenhum processo de extracao ou preparo de amostra foi necessario nas analises de DESI e EASI e os resultados obtidos sugerem portanto a possibilidade de uso dessas duas tecnicas para um rapido controle qualitativo e processos de certificacao de amostras de cafe.

Blends of soybean biodiesel with petrodiesel: direct quantitation via mass spectrometry

Quantitation and identification of blends of soybean biodiesel with petrodiesel were performed via mass spectrometry using two ionization techniques: electrospray ionization (ESI) and Venturi easy ambient sonic-spray ionization in its liquid mode (VL-EASI). Different soybean biodiesel/petrodiesel blends (from B0 to B100) were diluted and then directly infused and analyzed by both techniques. To investigate adulteration of Bn blends, different soybean oil/biodiesel and soybean oil/petrodiesel blends were analyzed. Analytical curves were obtained in three replicates. The two techniques were shown to provide reasonably accurate quantitation in the B1-B20 range. These techniques were also successfully used to detect contamination or adulteration of Bn blends with vegetable oils. ESI is a widely used and commercially available technique whereas a VL-EASI source can be easily mounted using common laboratory parts requiring no use of high voltages. Both techniques require no pre-separation or derivatization steps and offer, therefore, simple and fast methods for the quantitation of Bn blends. The comprehensive snapshots of the molecular composition also allow quality control and typification of the biodiesel and eventually of the vegetable oils in illegal admixtures.

Fast direct determination of titanium dioxide in toothpastes by X-Ray fluorescence and multivariate calibration

Recentemente, o dioxido de titânio foi classificado como potencialmente carcinogenico pela International Agency for Research on Cancer (IARC). Dioxido de titânio e um pigmento geralmente utilizado como opacificante em cremes dentais, porem sua concentracao nao e indicada nos rotulos dos produtos. Neste estudo, 22 amostras de cremes dentais foram calcinadas a 800 oC e o teor de TiO2 foi determinado por fluorescencia de raios X por energia dispersiva (EDXRF) atraves do metodo de parâmetros fundamentais (FP). As mesmas amostras foram irradiadas in natura por 100 s e, atraves da correlacao dos espectros e das concentracoes anteriormente determinadas, um modelo multivariado de calibracao foi construido. Oito variaveis latentes descreveram o modelo de regressao de minimos quadrados parciais (PLS) com erros medios de 9,5%, indicando que alem do pico referente ao titânio, as informacoes do espalhamento da radiacao tambem sao importantes para minimizar os erros ao usar uma calibracao univariada. A rapidez das analises, com minimo pre-tratamento das amostras, e a grande vantagem do metodo, que tem frequencia analitica de 24 determinacoes por hora.

Direct Visualization of Neurotransmitters in Rat Brain Slices by Desorption Electrospray Ionization Mass Spectrometry Imaging (DESI - MS)

AbstractMass spectrometry imaging (MSI) of neurotransmitters has so far been mainly performed by matrix-assisted laser desorption/ionization (MALDI) where derivatization reagents, deuterated matrix and/or high resolution, or tandem MS have been applied to circumvent problems with interfering ion peaks from matrix and from isobaric species. We herein describe the application of desorption electrospray ionization mass spectrometry imaging (DESI)-MSI in rat brain coronal and sagittal slices for direct spatial monitoring of neurotransmitters and choline with no need of derivatization reagents and/or deuterated materials. The amino acids γ-aminobutyric (GABA), glutamate, aspartate, serine, as well as acetylcholine, dopamine, and choline were successfully imaged using a commercial DESI source coupled to a hybrid quadrupole-Orbitrap mass spectrometer. The spatial distribution of the analyzed compounds in different brain regions was determined. We conclude that the ambient matrix-free DESI-MSI is suitable for neurotransmitter imaging and could be applied in studies that involve evaluation of imbalances in neurotransmitters levels. Graphical Abstractᅟ

A dopant for improved sensitivity in easy ambient sonic‐spray ionization mass spectrometry

Recently, 3-nitrobenzonitrile (3-NBN) has been used to improve sensitivity of sonic-spray ionization mass spectrometry. Easy ambient sonic-spray ionization (EASI) is one of the simplest, gentlest and most used spray-based desorption/ionization ambient techniques, but limited sensitivity has been commonly taken as its major drawback. Herein we investigate the use of 3-NBN as a dopant in EASI-MS for improved sensitivity. Using a few typical EASI samples as test cases, the presence of 10 ppm (µg ml(-1) ) of 3-NBN in the spray solvent showed two to fourfold gains in EASI-MS sensitivity as measured both by total ion current and S/N ratios, accompanied with significant reductions in chemical noise. Sensitivity for DESI using 3-NBN as a dopant also improved and dopant DESI versus dopant EASI sensitivities were compared. The use of solvent dopants seems therefore to be a promising strategy to improve sensitivity for spray-based ambient MS techniques. Copyright