Showing papers on "Atmospheric-pressure chemical ionization published in 2012"
TL;DR: A detailed investigation of twelve carotenes and xanthophylls was carried out using both positive ion and negative ion APCI tandem mass spectrometry with collision-induced dissociation, and characteristic fragment ions were identified that may be used to distinguish between carotenoids.
154 citations
TL;DR: Data is presented suggesting that the prompt and delayed ionization reported for vacuum MALDI are both fast processes relative to producing highly charged ions by LSI, and charged droplets/droplets may be a common link for ionization of nonvolatile compounds by a variety of MS ionization methods, including LSI.
115 citations
TL;DR: The SPE-LC/tqMS method was successfully applied to quantify 13 HAcAms in drinking water samples for the first time, and first indentified tribromo acetamide and chloroiodoacetamide as DBPs in drinkingWater.
106 citations
TL;DR: The investigation of the atmospheric pressure laser ionization (APLI) technique coupled with Fourier transform ion cyclotron resonance mass spectrometer to analyze the asphaltene fraction of a crude oil showed that APLI expands the range of the assigned molecules, while retaining information already observed with the generally used ion sources.
Abstract: Over the years, ultrahigh resolution mass spectrometry has successfully illustrated the extreme complexity of crude oil and related solubility or polarity based fractions on a molecular level. However, the applied ionization technique greatly influences the outcome and may provide misleading information. In this work, we investigate the atmospheric pressure laser ionization (APLI) technique coupled with Fourier transform ion cyclotron resonance mass spectrometer to analyze the asphaltene fraction of a crude oil. These results were compared to data obtained by using other existing atmospheric pressure ionization methods. Furthermore elemental analysis and solid state NMR were used to obtain the bulk characteristics of the asphaltene sample. The results of the different ionization techniques were compared with the bulk properties in order to describe the potential discrimination effects of the ionization techniques that were observed. The results showed that APLI expands the range of the assigned molecules,...
92 citations
TL;DR: This highly specific HPLC-MS/MS method is suitable for vitamin D profiling and resulted in the detection of considerable amounts of 3-epi-25OH-D(3) and 24R,25(OH)(2)-D( 3).
74 citations
TL;DR: High-performance liquid chromatography (HPLC) is usually coupled with a universal mass spectrometry detector (MS) (or tandem mass spectromaetry detector MS-MS), what allows for detection, identification and quantification the various compounds in a particular group of surfactants in suitably prepared solvent extracts.
74 citations
TL;DR: Relative ionization efficiencies (RIEs) for a large group of compound families were determined with LTP-Orbitrap-MS and compared to those obtained with electrospray ionization mass spectrometry (ESI-MS) and atmospheric pressure chemical ionizationmass spectromaetry (APCI-MS).
Abstract: Ambient desorption/ionization mass spectrometry (ADI-MS) is an attractive method for direct analysis with applications in homeland security, forensics, and human health. For example, low-temperature plasma probe (LTP) ionization was successfully used to detect, e.g., explosives, drugs, and pesticides directly on the target. Despite the fact that the field is gaining significant attention, few attempts have been made to classify ambient ionization techniques based on their ionization characteristics and performance compared to conventional ionization sources used in mass spectrometry. In the present study, relative ionization efficiencies (RIEs) for a large group of compound families were determined with LTP-Orbitrap-MS and compared to those obtained with electrospray ionization mass spectrometry (ESI-MS) and atmospheric pressure chemical ionization mass spectrometry (APCI-MS). RIEs were normalized against one reference compound used across all methods to ensure comparability of the results. Typically, LTP analyte ionization through protonation/deprotonation (e.g., 4-acetamidophenol) was observed; in some cases (e.g., acenaphthene) radicals were formed. Amines, amides, and aldehydes were ionized successfully with LTP. A benefit of LTP over conventional methods is the possibility to successfully ionize PAHs and imides. Here, the studied model compounds could be detected by neither APCI nor ESI. LTP is a relatively soft ionization method because little fragmentation of model compounds was observed. It is considered to be an attractive method for the ionization of low molecular weight compounds over a relatively wide polarity range.
73 citations
TL;DR: The results presented in this paper demonstrate the potential of APCI as new source for GC/MS that could be applied to other analytical problems apart from those illustrated in this work.
Abstract: Gas chromatography coupled to mass spectrometry (GC/MS) has been extensively applied for determination of volatile, nonpolar, compounds in many applied fields like food safety, environment, or toxicology. The wide majority of methods reported use electron ionization (EI), which may result in extensive fragmentation of analytes compromising selectivity and sensitivity. This might also complicate the application of tandem MS due to lack of specific/abundant precursor ions. Pyrethroids are examples of compounds with this behavior. In this work, the potential of atmospheric pressure chemical ionization (APCI), a softer form of ionization, combined with GC and a triple quadrupole mass analyzer was investigated, taking pyrethroids as a case study and their determination in fruit and vegetables as example application. Ionization and fragmentation behavior of eight pyrethroids (bifenthrin, cyfluthrin, cypermethrin, permethrin, λ-cyhalothrin, fluvalinate, fenvalerate, and deltamethrin) by APCI were studied. The formation of a highly abundant (quasi) molecular ion was the main goal because of the enhanced selectivity when used as precursor ion in tandem MS. The addition of water as a modifier was tested to promote the generation of protonated molecules, resulting in notable improvement of sensitivity and selectivity for most compounds. The excellent detectability (low detection limits (LODs) <20 fg achieved) when using APCI combined with state-of-the-art tandem MS was demonstrated for real samples. Additionally, matrix effects were evaluated in terms of signal enhancement/suppression. Depending on the matrix, different degrees of suppression were observed, on average reducing the signal in matrix to 55% of that in solvent. The results presented in this paper demonstrate the potential of APCI as new source for GC/MS that could be applied to other analytical problems apart from those illustrated in this work.
68 citations
TL;DR: This quantitation method yields good recoveries with variable lipid-content samples, avoids antibody cross-reactivity issues, and delivers results for multiple steroids, and can enrich datasets by providing simultaneous quantitation of multiple steroids.
Abstract: Blood samples from wild mammals and birds are often limited in volume, allowing researchers to quantify only one or two steroids from a single sample by immunoassays. In addition, wildlife serum or plasma samples are often lipemic, necessitating stringent sample preparation. Here, we validated sample preparation for simultaneous liquid chromatography – tandem mass spectrometry (LC-MS/MS) quantitation of cortisol, corticosterone, 11-deoxycortisol, dehydroepiandrosterone (DHEA), 17β-estradiol, progesterone, 17α-hydroxyprogesterone and testosterone from diverse mammalian (7 species) and avian (5 species) samples. Using 100 µL of serum or plasma, we quantified (signal-to-noise (S/N) ratio ≥10) 4–7 steroids depending on the species and sample, without derivatization. Steroids were extracted from serum or plasma using automated solid-phase extraction where samples were loaded onto C18 columns, washed with water and hexane, and then eluted with ethyl acetate. Quantitation by LC-MS/MS was done in positive ion, multiple reaction-monitoring (MRM) mode with an atmospheric pressure chemical ionization (APCI) source and heated nebulizer (500°C). Deuterated steroids served as internal standards and run time was 15 minutes. Extraction recoveries were 87–101% for the 8 analytes, and all intra- and inter-run CVs were ≤8.25%. This quantitation method yields good recoveries with variable lipid-content samples, avoids antibody cross-reactivity issues, and delivers results for multiple steroids. Thus, this method can enrich datasets by providing simultaneous quantitation of multiple steroids, and allow researchers to reimagine the hypotheses that could be tested with their volume-limited, lipemic, wildlife samples.
67 citations
TL;DR: A rapid and reliable method enabling high-throughput sample analysis for quicker data generation, detection, and monitoring of CBZ in WW and WWS was developed and validated and showed the best extraction efficiency with methanol as compared to USE and MAE.
63 citations
TL;DR: There are many variables to consider when using LC-MS/MS, including assay standardisation/calibration, chromatography and MS conditions, and Laboratories should always subscribe to an EQA scheme for 25OHD analysis.
TL;DR: In this article, a robust method for the simultaneous determination of vitamins A, E and β-carotene using high performance liquid chromatography-ion trap mass spectrometry (HPLC-MSn) was described.
TL;DR: The use of a mobile phase of high pH resulted in higher retention and higher electrospray ionization signals than the conventional low pH mobile phases, and the benefits of a high pH mobile phase on both chromatography and mass spectrometry should be encouraged.
TL;DR: The objective of this work was to provide background to the choice of the most appropriate source in order to analyze complex organic mixtures as those encountered in polluted soils, water, sediments, as well as in petroleum.
TL;DR: The soft and reproducible ionization in the APCI source has greatly favored the formation of [M+H]+ oppositely to EI where abundant fragmentation occurs and where the molecular ions have low abundance or are even absent in the mass spectrum.
TL;DR: In this paper, a positive ion mode electrospray ionization (ESI) doped with sodium chloride was used to obtain abundant adduct ions with no accompanying fragmentation.
TL;DR: The use of this approach further extends the coverage of current LC/MS methods towards an even larger variety of chemical species including both polar and nonpolar (non-ESI amenable) species and may find several applications in fields such as food and environment testing or metabolomics where GC/MS andLC/MS are combined to cover as many different species as possible.
Abstract: A Dielectric Barrier Discharge Ionization (DBDI) LC/MS interface is based on the use of a low-temperature helium plasma, which features the possibility of simultaneous ionization of species with a wide variety of physicochemical properties. In this work, the performance of LC/DBDI-MS for trace analysis of highly relevant species in food and environment has been examined. Over 75 relevant species including multiclass priority organic contaminants and residues such as pesticides, polycyclic aromatic hydrocarbons, organochlorine species, pharmaceuticals, personal care products, and drugs of abuse were tested. LC/DBDI-MS performance for this application was assessed and compared with standard LC/MS sources (electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI)). The used benchtop Orbitrap mass spectrometer features a 10 Hz polarity switching mode, so that both positive and negative ion mode acquisitions are possible with acquisition cycles matching the requirements of fast liquid chromatography. Both polar and nonpolar species (including those typically analyzed by GC/electron ionization-MS) can be tested in a single run using polarity switching mode. The methodology was found to be effective in detecting a wide array of organic compounds at concentration levels in the low ng L−1 to μg kg−1 range in wastewater and food matrices, respectively. The linearity was evaluated in an olive oil extract, obtaining good correlation coefficients in the studied range. Additionally, minor matrix effects (≤15% of signal suppression or enhancement) were observed for most of the studied analytes in this complex fatty matrix. The results obtained were compared with data from both ESI and APCI sources, obtaining a merged coverage between ESI and APCI in terms of analyte ionization and higher overall sensitivity for the proposed ion source based on the DBD principle. The use of this approach further extends the coverage of current LC/MS methods towards an even larger variety of chemical species including both polar and nonpolar (non-ESI amenable) species and may find several applications in fields such as food and environment testing or metabolomics where GC/MS and LC/MS are combined to cover as many different species as possible.
TL;DR: In this paper, the authors demonstrate the application of corona discharge ion mobility spectrometry with orthogonal acceleration time of flight mass spectrometers for volatile organic compounds (VOCs) monitoring.
Abstract: We demonstrate the application of corona discharge ion mobility spectrometry with orthogonal acceleration time of flight mass spectrometry (CD IMS-oaTOF) for volatile organic compounds (VOCs) monitoring. Two-dimensional (2D) IMS-oaTOF spectra of VOCs were recorded in nearly real time. The corona discharge atmospheric pressure chemical ionization (APCI) source was operated in positive mode in nitrogen and air. The CD ion source generates in air H(3)O(+)(H(2)O)(n) and NO(+). The NO(+) offers additional possibility for selective ionization and for an increase of the sensitivity of monoaromatic compounds. In addition to H(3)O(+)(H(2)O)(n) and NO(+), we have carried out ionization of VOCs using acetone as dopant gas ((CH(3))(2)COH(+)). Sixteen model VOCs (tetrahydrofuran, butanol, n-propanol, iso-propano, acetone, methanol, ethanol, toluene, benzene, amomnia, dioxan, triethylamine, acetonitrile, formaldehyde, m-xylene, 2,2,2-trifluoroethylamine) were tested using these ionization techniques.
Journal Article•
TL;DR: A comparison of electrospray ionization, atmospheric pressure chemical ionization and atmospheric pressure photoionization for the analysis of a wide range of lipids has been performed on standard mixtures and extracts of Leishmania donovani promastigotes resistant to Amphotericin B, with APPI providing the highest signal, signal-to-noise (S/N), and sensitivity.
Abstract: A comparison of electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI) and atmospheric pressure photoionization (APPI) for the analysis of a wide range of lipids has been performed on standard mixtures and extracts of Leishmania donovani promastigotes resistant to Amphotericin B (AmB). Calibration model, precision, limits of detection and quantification (LOD and LOQ) were assessed for each source. APPI provided the highest signal, signal-to-noise (S/N), and sensitivity for non-polar and low-polarity lipids, while ESI and APCI gave better results for the most polar ones. The linear model was valid for all lipids, except for one class with APPI, six classes with ESI, and eleven classes with APCI. LODs ranged from 0.2 to 20 µg mL–1 for ESI, from 0.1 to 10 µg mL–1 for APCI, and from 0.02 to 9.5 µg mL–1 for APPI. LOQs ranged from 0.2 to 61 µg mL–1 for ESI, from 0.4 to 31 µg mL–1 for APCI, and from 0.1 to 29 µg mL–1 for APPI. Each source provided similar lipid composition and variations in a comparison of three different L. donovani samples: miltefosine-treated, miltefosine-resistant and treated miltefosine-resistant parasites. A treated miltefosine-resistant sample was finally analyzed with each ion source in order to verify that the same lipid molecular species are detected.
TL;DR: Several SPE parameters were evaluated in order to optimize recovery efficiencies when extracting analytes from wastewater, such as the nature of the stationary phase, the loading flow rate, the extraction pH, the volume and composition of the washing solution and the initial sample volume.
TL;DR: Fullerene APPI negative mass spectra were dominated by the isotopic cluster of the molecular ion, although isotopic patterns for M+1, M+2, and M+3 ions showed higher than expected relative abundances.
Abstract: Atmospheric pressure photoionization (APPI) was evaluated for the analysis of fullerenes. An important response improvement was found when using toluene mediated APPI in negative mode if compared with other atmospheric pressure ionization (API) sources (electrospray and atmospheric pressure chemical ionization). Fullerene APPI negative mass spectra were dominated by the isotopic cluster of the molecular ion, although isotopic patterns for M+1, M+2, and M+3 ions showed higher than expected relative abundances. These discrepancies are explained by the presence of two isobaric ions, one due to 13C and the other due to the addition of hydrogen to a double bond of the fullerene structure. Triple quadrupole tandem mass spectrometry, ultrahigh resolution mass spectrometry, and accurate mass measurements were used to confirm these assignments. Additionally, cluster ions M+16 and M+32 were characterized following the same strategy. Ions due to the addition of oxygen and alkyl additions were attributed to the prese...
TL;DR: A new coating material was used for a stir bar sorptive extraction method coupled to a high throughput sample analysis technique that could prove to be useful method for the detection and quantification of trace levels of steroid hormones.
TL;DR: The overall speciation of nonpolar, aliphatic hydrocarbon base oil species offers a promising diagnostic probe to characterize crude oil and its products.
Abstract: We present atmospheric pressure laser-induced acoustic desorption chemical ionization (AP/LIAD-CI) with O2 carrier/reagent gas as a powerful new approach for the analysis of saturated hydrocarbon mixtures. Nonthermal sample vaporization with subsequent chemical ionization generates abundant ion signals for straight-chain, branched, and cycloalkanes with minimal or no fragmentation. [M – H]+ is the dominant species for straight-chain and branched alkanes. For cycloalkanes, M+• species dominate the mass spectrum at lower capillary temperature ( 200 °C). The mass spectrum for a straight-chain alkane mixture (C21–C40) shows comparable ionization efficiency for all components. AP/LIAD-CI produces molecular weight distributions similar to those for gel permeation chromatography for polyethylene polymers, Polywax 500 and Polywax 655. Coupling of the technique to Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) for the analysis of complex hydrocar...
TL;DR: A comparison of electrospray ionization (ESI), atmospheric pressure chemical ionization and atmospheric pressure photoionization (APPI) for the analysis of a wide range of lipids has been performed on standard mixtures and extracts of Leishmania donovani promastigotes resistant to Amphotericin B (AmB).
TL;DR: Extractive electrospray ionization mass spectrometry (EESI-MS) has been shown, in other laboratories, to be a useful technique for the analysis of aerosols from a variety of sources as discussed by the authors.
Abstract: Extractive electrospray ionization mass spectrometry (EESI-MS) has been shown, in other laboratories, to be a useful technique for the analysis of aerosols from a variety of sources. EESI-MS is applied here, for the first time, to the analysis of secondary organic aerosol (SOA) formed from the reaction of ozone and α-pinene. The results are compared to those obtained using atmospheric pressure chemical ionization mass spectrometry (APCI-MS). The SOA was generated in the laboratory and merged with electrospray droplets. The recovered ions were directed towards the inlet of a triple quadrupole mass spectrometer. Through the use of a denuder to remove gas phase compounds, the EESI-MS technique was found to be effective for measuring the major ozonolysis products either in particles alone or in a combination of vapor phase and particulate products. Due to its relatively simple setup and the avoidance of sample collection and work-up, EESI-MS shows promise as an excellent tool for the characterization of atmospherically relevant particles.
TL;DR: Twenty-eight TAGs from the peanut oil and forty-four from the mouse liver were identified based on the TAGs' retention behaviors on the comprehensive two-dimensional LC system and their APCI MS fragments.
TL;DR: The proposed method makes use of a modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) procedure that combines isolation of the pesticides and sample cleanup in a single step, fulfilling the EC point system requirement for identification of contaminants in samples.
Abstract: This paper reports a novel approach for the detection, confirmation, and quantification of 15 selected pyrethroid pesticides, including pyrethins, and two metabolites of dithiocarbamates in foods by ultra-performance liquid chromatography–tandem mass spectrometry (UPLC–MS–MS). The proposed method makes use of a modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) procedure that combines isolation of the pesticides and sample cleanup in a single step. Analysis of pyrethroids and dithiocarbamate metabolites was performed by UPLC–MS–MS operated with electrospray and atmospheric pressure chemical ionization, respectively. Two specific precursor–product ion transitions were acquired per target compound in multiple reaction monitoring (MRM) mode. Such acquisition achieved the minimum number of identification points according to European Commission (EC) document no. SANCO/10684/2009, thus fulfilling the EC point system requirement for identification of contaminants in samples. The method was validated with a variety of food samples. Calibration curves were linear and covered from 1 to 800 μg kg−1 in the sample for all target compounds. Average recoveries, measured at mass fractions of 10 and 100 μg kg−1 for pyrethroids and 5 and 50 μg kg−1 for dithiocarbamate metabolites, were in the range of 70–120% for all target compounds with relative standard deviations below 20%. Method limits of quantification (MLOQ) were 10 μg kg−1 and 5 μg kg−1 for pyrethroids and dithiocarbamate metabolites, respectively. The method has been successfully applied to the analysis of 600 food samples in the course of the first Hong Kong total diet study with pyrethroids and metabolites of dithiocarbamates being the pesticides determined.
TL;DR: A highly sensitive liquid chromatography tandem mass spectrometry method was developed for simultaneous analysis of 9 narcotic analgesics and metabolites in urine and whole blood and showed very high sensitivity.
TL;DR: The feasibility of using this ionization method on the chromatographic time scale was demonstrated by using high-performance liquid chromatography (HPLC) with hexane as the mobile phase (and APCI reagent) to separate an artificial mixture prior to mass spectrometric analysis.
TL;DR: This study described a fully automated method using on-line solid phase extraction of large volume injections coupled with high performance liquid chromatography (HPLC) and tandem mass spectrometry (MS/MS) to simultaneously detect a group of recalcitrant microconstituents (pharmaceuticals and personal care products, steroid hormones and sterols) in aqueous matrices.
Abstract: This study described a fully automated method using on-line solid phase extraction of large volume injections coupled with high performance liquid chromatography (HPLC) and tandem mass spectrometry (MS/MS) to simultaneously detect a group of recalcitrant microconstituents (pharmaceuticals and personal care products, steroid hormones and sterols) in aqueous matrices. Samples (1 mL to 20 mL) were loaded to the preconcentration column at 1 mL/min, and the column was washed with 1000 μL of 25% methanol in LC/MS water to remove polar and ionic interferences before LC-MS/MS analysis. Three different atmospheric pressure ionization (API) techniques, including photoionization (APPI) with four different dopants (acetone, anisole, chlorobenzene and toluene), heated electrospray ionization (HESI) and atmospheric pressure chemical ionization (APCI), were evaluated on the basis of method detection limits (MDLs) and recoveries from different aqueous matrixes. Results indicated that APPI with toluene as dopant was the most sensitive ionization method for the majority of the analytes. When using 5 mL of sample, MDLs for pharmaceuticals and personal care products, including carbamazepine, DEET, caffeine, naproxen, acetaminophen and primidone, were between 0.3 ng/L and 15 ng/L. MDLs of hormones, including testosterone, equilenin, progesterone, equilin, 17β-estradiol, 17α-ethynylestradiol, estrone, androsterone, mestranol and estriol, were between 1.2 ng/L and 37 ng/L. The combination of APPI with dopant allowed the detection of two difficult to ionize fecal related sterols, such as coprostan-3-ol and coprostan-3-one with MDLs of 5.4 ng/L and 11 ng/L, respectively. Calculated MDLs are more than adequate for analysis of wastewater using 1 to 5 mL sample size and for surface waters using up to 20 mL sample size. Copyright © 2012 John Wiley & Sons, Ltd.