Direct Chemical Ionization Mass Research Articles

Early detection of algal infection using direct real-time chemical ionization mass spectrometry

Early detection of algal infection using direct real-time chemical ionization mass spectrometry Robert S. Pomeroy, Teaching Professor at UC San Diego, guides us through the early detection of algal infections using direct real-time chemical ionization mass spectrometry. Petroleum, from the Latin “rock oil,” has transformed our lives. It has changed how we live, work, and play. Petroleum is, however, nothing more than ancient algae. The transformation of biomass to hydrocarbons results from being subjected to heat and pressure over millions of years. Algae accumulate oils that, when extracted, can be converted into renewable fuels such as gasoline, diesel, and jet fuel. In 1978, the U.S. Department of Energy launched the Aquatic Species Program to investigate energy production using algae. (1) The establishment of this program coincided with the rapidly rising fuel cost due to the Oil Embargo in 1973 and led to the creation of the U.S. Department of Energy.

Chemical Constituents and Cytotoxic Activity of Rhinella jimi (Anura: Bufonidae)

Rhinella jimi toads (Stevaux, 2002) belong to the Bufonidae family, are endemic in the Brazilian Northeast and are commonly found during rainy periods. In general, amphibians of this family have in their poisons different metabolites that show a diversity of pharmacological activities. The isolation and identification of these compounds are of great importance, and techniques such as high-performance liquid chromatography coupled to mass spectrometry are widely used for the discovery of novel and known compounds in these poisons. For R. jimi poison, the ethyl acetate and methanolic extracts were obtained and thirty compounds were identified by combining ultra-performance liquid chromatography coupled to mass spectrometry (UPLC-MS) with direct infusion atmospheric pressure chemical ionization mass spectrometry (DI-APCI-MS/MS) and direct infusion electrospray mass spectrometry (DI-ESI-MS/MS) for each extract, respectively. Marinobufagin (2) and marinobufotoxin (19) were the majorities of each extract, respectively. In addition, other bufadienolides mainly present in the ethyl acetate extract, such other bufotoxins, alkaloids and arginine diacid derivatives were identified in the methanol extract. In a cytotoxic assay by 3-(4,5-dimethylthiazol-2-yl)-2,5‑diphenyltetrazolium bromide (MTT), the extracts and compound 2 demonstrated half-maximal inhibitory concentration (IC50) values better than the positive control doxorubicin, evidencing excellent cytotoxic. This is the most complete study of the chemical composition of R. jimi toad poison and its respective cytotoxic activity, promoting the enrichment of knowledge about this family and species.

Regio- and Stereo-Specific Chemical Depolymerization of High Molecular Weight Polybutadiene and Polyisoprene for Their Analysis by High-Resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry: Comparison with Pyrolysis-Comprehensive Two-Dimensional Gas Chromatography/Mass Spectrometry, Atmospheric Solid Analysis Probe, Direct Inlet Probe-Atmospheric Pressure Chemical Ionization Mass Spectrometry, and Ion Mobility Spectrometry-Mass Spectrometry.

Polybutadiene (PB) and polyisoprene (PI), the two most common polydienes (PD), are involved in a large number of materials and used in a wide variety of applications. The characterization of these polymers by mass spectrometry (MS) continues to be very challenging due to their high insolubility and the difficulty to ionize them. In this work, a cross-metathesis reaction was used to generate end-functionalized acetoxy ionizable oligomers for the structural deciphering of different commercial PB and PI samples. A cross-metathesis reaction was carried out between polymers and the Z-1,4-diacetoxy-2-butene as a chain transfer agent in dichloromethane using a Hoveyda-Grubbs second-generation catalyst. Well-defined acetoxy telechelic structures were obtained and analyzed by Fourier transform ion cyclotron resonance (FTICR) high-resolution MS. However, after depolymerization, low molar mass polyolefins contained some units with different configurations, suggesting an olefin isomerization reaction due to the decomposition of the catalyst. The addition of an electron-deficient reagent such as 2,6-dichloro-1,4-benzoquinone suppressed this isomerization in the case of both Z- and E-PB and PI. Ion mobility spectrometry-mass spectrometry (IMS-MS) and energy-resolved tandem mass spectrometry (ERMS) analyses confirmed a successful isomerization suppression. For comparing the results obtained by depolymerization with classical methods for polymer analysis, pyrolysis-comprehensive two-dimensional gas chromatography/mass spectrometry (Py-GC × GC-MS), atmospheric solid analysis probe (ASAP), and direct inlet probe-atmospheric pressure chemical ionization (DIP-APCI) analyses were performed on the same polymers. This strategy can be applied on a variety of synthetic and natural not yet characterized polymers.

Trace level analysis of three glycol ethers in wood stains by APCI-LC-MS/MS

A direct injection liquid chromatography tandem atmospheric pressure chemical ionization mass spectrometry method was developed for determination of diethylene glycol methyl ether, dipropylene glycol butyl ether, and dipropylene glycol methyl ether.

Comparison of Atmospheric Pressure Chemical Ionization and Field Ionization Mass Spectrometry for the Analysis of Large Saturated Hydrocarbons.

Direct infusion atmospheric pressure chemical ionization mass spectrometry (APCI-MS) was compared to field ionization mass spectrometry (FI-MS) for the determination of hydrocarbon class distributions in lubricant base oils. When positive ion mode APCI with oxygen as the ion source gas was employed to ionize saturated hydrocarbon model compounds (M) in hexane, only stable [M - H]+ ions were produced. Ion-molecule reaction studies performed in a linear quadrupole ion trap suggested that fragment ions of ionized hexane can ionize saturated hydrocarbons via hydride abstraction with minimal fragmentation. Hence, APCI-MS shows potential as an alternative of FI-MS in lubricant base oil analysis. Indeed, the APCI-MS method gave similar average molecular weights and hydrocarbon class distributions as FI-MS for three lubricant base oils. However, the reproducibility of APCI-MS method was found to be substantially better than for FI-MS. The paraffinic content determined using the APCI-MS and FI-MS methods for the base oils was similar. The average number of carbons in paraffinic chains followed the same increasing trend from low viscosity to high viscosity base oils for the two methods.

CF3+ and CF2H+: new reagents for n-alkane determination in chemical ionisation reaction mass spectrometry.

Alkanes provide a particular analytical challenge to commonly used chemical ionisation methods such as proton-transfer from water owing to their basicity. It is demonstrated that the fluorocarbon ions CF3+ and CF2H+, generated from CF4, as reagents provide an effective means of detecting light n-alkanes in the range C2-C6 using direct chemical ionisation mass spectrometry. The present work assesses the applicability of the reagents in Chemical Ionisation Mass Spectrometric (CI-TOF-MS) environments with factors such as high moisture content, operating pressures of 1-10 Torr, accelerating electric fields (E/N) and long-lived intermediate complex formation. Of the commonly used chemical ionisation reagents, H3O+ and NO+ only react with hexane and higher while O2+ reacts with all the target samples, but creates significant fragmentation. By contrast, CF3+ and CF2H+ acting together were found to produce little or no fragmentation. In dry conditions with E/N = 100 Td or higher the relative intensity of CF2H+ to CF3+ was mostly less than 1% but always less than 3%, making CF3+ the main reagent ion. Using O2+ in a parallel series of experiments, a substantially greater degree of fragmentation was observed. The detection sensitivities of the alkanes with CF3+ and CF2H+, while relatively low, were found to be better than those observed with O2+. Experiments using alkane mixtures in the ppm range have shown the ionisation technique based on CF3+ and CF2H+ to be particularly useful for measurements of alkane/air mixtures found in polluted environments. As a demonstration of the technique's effectiveness in complex mixtures, the detection of n-alkanes in a smoker's breath is demonstrated.

Rapid recognition of bacteremia in humans using atmospheric pressure chemical ionization mass spectrometry of volatiles emitted by blood cultures

Human bacteremia is rapidly diagnosed by direct atmospheric pressure chemical ionization mass spectrometry analysis of blood culture volatiles.

Rapid on-site detection of explosives on surfaces by ambient pressure laser desorption and direct inlet single photon ionization or chemical ionization mass spectrometry

Considering current security issues, powerful tools for detection of security-relevant substances such as traces of explosives and drugs/drug precursors related to clandestine laboratories are required. Especially in the field of detection of explosives and improvised explosive devices, several relevant compounds exhibit a very low vapor pressure. Ambient pressure laser desorption is proposed to make these substances available in the gas phase for the detection by adapted mass spectrometers or in the future with ion-mobility spectrometry as well. In contrast to the state-of-the-art thermal desorption approach, by which the sample surface is probed for explosive traces by a wipe pad being transferred to a thermal desorber unit, by the ambient pressure laser desorption approach presented here, the sample is directly shockwave ablated from the surface. The laser-dispersed molecules are sampled by a heated sniffing capillary located in the vicinity of the ablation spot into the mass analyzer. This approach has the advantage that the target molecules are dispersed more gently than in a thermal desorber unit where the analyte molecules may be decomposed by the thermal intake. In the technical realization, the sampling capillary as well as the laser desorption optics are integrated in the tip of an endoscopic probe or a handheld sampling module. Laboratory as well as field test scenarios were performed, partially in cooperation with the Federal Criminal Police Office (Bundeskriminalamt, BKA, Wiesbaden, Germany), in order to demonstrate the applicability for various explosives, drugs, and drug precursors. In this work, we concentrate on the detection of explosives. A wide range of samples and matrices have been investigated successfully.

Characterization of Polyurethane Formulations by Direct Probe Atmospheric Pressure Chemical Ionization Mass Spectrometry

Abstract Complex, commercially available polyurethane polymers were heated at slowly increasing temperatures on a direct probe (DP) inserted into an atmospheric pressure chemical ionization (APCI) source of a quadrupole ion trap mass spectrometer. Slow heating of the probe allowed for temporal separation of the thermally desorbed components (such as additives) and thermal degradation products, based on their volatilities and bond stabilities. In situ analysis of the released desorption products and pyrolyzates was accomplished by APCI mass spectrometry. DP-APCI enabled the characterization of polyurethanes that cannot be analyzed directly by mass spectrometry. Distinctions could be made between polymer formulations with variable physical properties due to their different blends.

Evaluation of the oxidative status of virgin olive oils with different phenolic content by direct infusion atmospheric pressure chemical ionization mass spectrometry

Atmospheric pressure chemical ionization mass spectrometry was used to predict the oxidative status of virgin olive oils (VOO) during their storage. VOO samples, with and without phenolic compounds, were stored in the dark at 60 degrees C up to 7 weeks. The VOO samples were diluted in an alkaline propanol/methanol mixture and directly infused into an ion-trap mass spectrometer. The abundances of the [M-H](-) peaks of free fatty acids, oxidized fatty acids, tocopherols and phenolic compounds, jointly with their oxidized forms, were measured and used as predictors. Two linear discriminant analysis (LDA) models were constructed in order to classify samples according to their oxidative levels. The first model was constructed using both VOO samples (with and without phenols), considering as predictors only fatty acids and their oxidized products. The second LDA model was constructed with the VOO sample with phenolic compounds considering as predictors all the peaks measured. In both models, the samples divided in the eight different storage times were correctly classified (100%) by leave-one-out cross-validation with an excellent resolution among all the category pairs (for the first model Wilks' lambda, lambda(w) = 0.229 and for the second lambda(w) = 0.928). This method is a very fast tool for on-line monitoring of VOO oxidation status.

Direct exposure-(chemical ionisation)mass spectrometry for a rapid characterization of raw and archaeological diterpenoid resinous materials

Direct exposure chemical ionisation (isobutane) mass spectrometry (DE-CIMS) was examined for its suitability to quickly identify diterpenoid resinous materials in archaeological findings. The technique was tested on standard compounds and reference raw materials. It was found that DE-MS using chemical ionization by isobutane provided a mass spectral fingerprint of the organic material of the sample in just a few minutes. The main components were highlighted, thus allowing the identification of a diterpenoid resinous material from Pinaceae and to assess its degree of oxidation. Of particular interest was the possibility to distinguish between pine resin and pine pitch, which is not feasible with electron ionization at 70 eV. DE-(isobutane)CI was then successfully applied to a resinous archaeological substance sampled from the material contained in a Roman amphora (2nd–4th centuries AD) recovered from a waterlogged archaeological site in Liguria (Italy). The results prove the occurrence of a pitch from Pinaceae in the amphora.

Low-temperature pyrolysis products from a polyether-based urethane

The pyrolysis products from a polyether-based polyurethane were analyzed by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), direct probe chemical ionization mass spectrometry (CI-MS), and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). Pyrolysis of the urethane was found to ensue about 250°C in inert atmosphere. The initial degradation products (∼250–275°C) may be explained by three decomposition pathways. Dissociation to isocyanate and alcohol yields as pyrolyzates diphenylmethane diisocyanate, an ‘amine–isocyanate’, 1,4-butanediol, and hydroxyl-terminated polyurethane and polyether oligomers. Dissociation to amine, olefin, and carbon dioxide is less prevalent initially; this produces an amine-isocyanate, methylene dianiline, and butenyl-terminated polyurethane and polyether oligomers. ‘Intramolecular exchange’ produces cyclic urethane oligomers. At about 300°C, more oligomeric pyrolyzates are observed with aromatic amine and/or butenyl end groups. These indicate that contributions from dissociation to amine, olefin, and carbon dioxide increase with increasing degradation temperature. Also at about 300°C, some oligomeric pyrolyzates are observed that have alkyl and/or aldehyde end groups. These are formed via free radical processes. By 325°C, all nitrogen-containing oligomeric pyrolyzates have decomposed. The remaining nitrogen is in the form of methylene dianiline (MDA) or methylated MDA.

Molecular characterization of microgram amounts of oceanic colloidal organic matter by direct temperature-resolved ammonia chemical ionization mass spectrometry

Marine colloidal organic matter in coastal waters off the coast of the eastern United States (from Georges Bank and the Mid-Atlantic Bight) is characterized by means of direct temperature-resolved mass spectrometry (DT-MS). Chemical ionization (NH 3) appears to be a very appropriate ionization method for this material. The analytical data confirm the presence of a significant polysaccharide fraction consisting of neutral sugars (normal-, deoxy- and methylated aldoses), N-acetyl aminosugars and, possibly, acidic sugars. The methylated and N-acetyl aminosugars are considered as markers for a bacterial contribution. No evidence is found for polysaccharides with large homopolymeric domains, suggesting an origin distinct from the common structural polysaccharides that comprise major polymers in algae and higher plants. The TIC profiles, which express the number of ions produced as a function of the temperature, often show a bimodal distribution. This indicates that the colloidal matter consists of two fractions with different thermal stabilities and probably also different chemical stabilities. Multivariate “mapping” of the DT-MS spectra reveals that the chemical differences between these two fractions show remarkable conformity amongst samples collected at widespread locations. The relative abundance of the two fractions appears to depend on both depth and location. The more thermally stable fraction is relatively abundant in deep water samples and some surface waters of the Mid-Atlantic Bight.

Characterization of stereoisomeric furanosidic derivatives by direct chemical ionization mass spectrometry and liquid secondary ion mass spectrometry with tandem mass spectrometry. (Part II)

Characterization of stereoisomeric furanosidic derivatives by direct chemical ionization mass spectrometry and liquid secondary ion mass spectrometry with tandem mass spectrometry. (Part II)

Characterization of stereoisomeric furanosidic derivatives by direct chemical ionization mass spectrometry and liquid secondary ion mass spectrometry with tandem mass spectrometry. (Part II)

Characterization of stereoisomeric furanosidic derivatives by direct chemical ionization mass spectrometry and liquid secondary ion mass spectrometry with tandem mass spectrometry. (Part II)

Biodegradable lubricants — Analysis of metalworking oils and hydraulic fluids by mass spectroscopy

AbstractBiodegradable metalworking oils and hydraulic fluids were screened for their base oil composition using a special mass spectrometric technique — direct exposure probe chemical ionisation mass spectrometry (CI(NH3)‐MS). All but one of the hydraulic fluid samples were rapeseed oil or trimethylolpropane trioleate based, the other sample being a neopentylglycol ester trimethylolpropane ester mixture. Ethylhexyl ester of rapeseed oil fatty acids (or similar) was present in some of the metalworking fluids in addition to rapeseed oil, whilst other samples were pure rapeseed oil. In several cases a trimethylolpropane/neopentylglycol ester base was found. Preliminary results for additive isolation/identification show the usefulness of preparative gel permeation chromatography.

Characterization of Stereoisomeric α-Methylene-γ-lactone Furanosidic Derivatives by Direct Chemical Ionization Mass Spectrometry and Liquid Secondary Ion Mass Spectrometry with Tandem Mass Spectrometry

Several furanosidic derivatives have been found to have biological activity and have been used both as fungicides and plant growth regulators. In particular, those carbohydrate derivatives that contain the α-methylene-γ-lactone unit have interesting potential applications. The present study deals with the mass spectrometric characterization of furanosidic compounds having a α-methylene-γ-lactone unit, using different ionization techniques: chemical ionization mass spectrometry and liquid secondary ion mass spectrometry together with metastable ion analysis and high-energy collision-induced dissociation. The objective of this study was to determine the influence on the respective fragmentation patterns of structural differences present in the stereoisomers. Common fragmentation differences relate to the extent of the loss of water which occurs together with the loss of acetone and to the formation of C7H7+ ions.

Characterization of Stereoisomeric α-Methylene-γ-lactone Furanosidic Derivatives by Direct Chemical Ionization Mass Spectrometry and Liquid Secondary Ion Mass Spectrometry with Tandem Mass Spectrometry

Several furanosidic derivatives have been found to have biological activity and have been used both as fungicides and plant growth regulators. In particular, those carbohydrate derivatives that contain the α-methylene-γ-lactone unit have interesting potential applications. The present study deals with the mass spectrometric characterization of furanosidic compounds having a α-methylene-γ-lactone unit, using different ionization techniques: chemical ionization mass spectrometry and liquid secondary ion mass spectrometry together with metastable ion analysis and high-energy collision-induced dissociation. The objective of this study was to determine the influence on the respective fragmentation patterns of structural differences present in the stereoisomers. Common fragmentation differences relate to the extent of the loss of water which occurs together with the loss of acetone and to the formation of C7H7+ ions.

Luminarin 9: A new fluorescent reagent for the precolumn derivatizatioin of main volatile and non-volatile N-nitrosamines in RP-HPLC

A sensitive precolumn fluorescence derivatization method for low level detection of the, volatile (N-nitrosodimethylamine and N-nitrosopyrrolidine) and non-volatile N-nitrosamines (N-nitrosoproline and N-nitrosodiethanolamine) an high-performance liquid chromatography was developed. This method is based on the denitrosation of the compounds of interest by a mixture of hydrobromic acid and acetic acid to produce the corresponding secondary amines. These are, then, able to react with, a quinolizinocoumarin derivative (luminarin 9®) to form highly fluorescent labelled N-nitrosamine derivatives. The structural elucidation of the luminarin 9® derivatives of N-nitrosoproline and N-nitrosodimethylamine by way of example, were established by liquid chromatography-mass spectrometry (LC-MS) and by direct chemical ionization-mass spectrometry (CI-MS). The separation, derivatization and detection conditioins were optimized for all the studied compounds. The detection limits (signal to noise ratio=3) were between 0.4 and 1.0 pmol injected depending on the compound. The calibration graphs were linear for derivatized amounts in the range of 0.5–40 nmol for N-nitrosodimethylamine and N-nitrosopyrrolidine, 0.4–2- nmol for N-nitrosoproline and 1.0–40 nmol for N-nitrosodiethanolamine. The repeatability (RSD less than 3.5%, n=6) and reproducibility (RSD less than 4.8%, n-6) were satisfactory.

Formation of 3,N4-ethenocytidine, 1,N6-ethenoadenosine, and 1,N2-ethenoguanosine in reactions of mucochloric acid with nucleosides.

Mucochloric acid, a genotoxic hydroxyfuranone found in chlorinated drinking water, was reacted with cytidine, adenosine, guanosine, and uridine. HPLC analyses with UV detection at 290 nm showed that one major product peak was formed in the reactions of cytidine, adenosine, and guanosine. The products formed in reactions carried out at 90 degrees C for 24 or 45 h were isolated by HPLC and characterized by 1H and 13C NMR spectroscopy, direct inlet chemical ionization mass spectrometry, and UV absorbance spectroscopy. The structures of the products were assigned to 3,N4-ethenocytidine, 1,N6-ethenoadenosine, and 1,N2-ethenoguanosine. In reactions performed at 37 degrees C and pH 7.0 the same compounds were detected after a reaction time of 7 days. No observable reaction took place between mucochloric acid and uridine.