Search results for "Ionization."
showing 10 items of 1229 documents
Ultrahigh-Resolution Mass Spectrometry in Real Time: Atmospheric Pressure Chemical Ionization Orbitrap Mass Spectrometry of Atmospheric Organic Aeros…
2018
The accurate and precise mass spectrometric measurement of organic compounds in atmospheric aerosol particles is a challenging task that requires analytical developments and adaptations of existing techniques for the atmospheric application. Here we describe the development and characterization of an atmospheric pressure chemical ionization Orbitrap mass spectrometer (APCI-Orbitrap-MS) for the measurement of organic aerosol in real time. APCI is a well-known ionization technique, featuring minimal fragmentation and matrix dependencies, and allows rapid alternation between the positive and negative ionization mode. As a proof of principle, we report ambient organic aerosol composition in rea…
Determination of acrylamide in coffee and chocolate by pressurised fluid extraction and liquid chromatography-tandem mass spectrometry.
2007
A selective and sensitive procedure has been developed and validated for the determination of acrylamide in difficult matrices, such as coffee and chocolate. The proposed method includes pressurised fluid extraction (PFE) with acetonitrile, florisil clean-up purification inside the PFE extraction cell and detection by liquid chromatography (LC) coupled to atmospheric pressure ionisation in positive mode tandem mass spectrometry (APCI-MS-MS). Comparison of ionisation sources (atmospheric pressure chemical ionisation (APCI), atmospheric pressure photoionization (APPI) and the combined APCI/APPI) and clean-up procedures were carried out to improve the analytical signal. The main parameters aff…
Bromine speciation in volcanic plumes: new in situ derivatization LC-MS method for the determination of gaseous hydrogen bromide by gas diffusion den…
2020
The chemical characterization of volcanic gas emissions gives insights into the interior of volcanoes. Monitoring of BrO/SO2-ratios has recently been correlated with changes in the activity of a volcano. BrO and SO2 can both be measured autonomously and simultaneously with the same instruments from a safe distance, making their ratio potentially a strong monitoring tool. However, BrO is not a primary emitted volcanic volatile and there exist still uncertainties about the formation of BrO in volcanic plumes, mostly due to the lack of analytical approaches for the accurate speciation of certain key compounds. This study describes a new method for the determination of the BrO precursor, the ga…
Fast Separation and Determination of Sterols in Vegetable Oils by Ultraperformance Liquid Chromatography with Atmospheric Pressure Chemical Ionizatio…
2010
A method for the determination of sterols in vegetable oils by ultraperformance liquid chromatography (UPLC) with atmospheric pressure chemical ionization mass spectrometry detection has been developed. The separation of sterols was optimized in terms of mobile phase composition, column temperature and flow rate. The optimal conditions were achieved using an Acquity UPLC BEH C18 column (50 x 2.1 mm, 1.7 microm) with a mobile phase consistent of acetonitrile/water (0.01% acetic acid) using a linear gradient, at a flow rate of 0.8 mL min(-1) and column temperature of 10 degrees C, giving a total analysis time below 5 min. The determination was performed in selective ion recording mode. The li…
Optimization of a microwave-assisted extraction large-volume injection and gas chromatography–ion trap mass spectrometry procedure for the determinat…
2006
Abstract A sensitive and rapid method for the determination of polybrominated diphenyl ethers (PBDEs), polybrominated biphenyls (PBBs) and polychlorinated naphthalenes (PCNs) in sediment samples is proposed. The method involving microwave-assisted extraction (MAE) and large-volume injection (LVI) gas chromatography (GC)–ion trap mass spectrometry (ITMS), and the experimental conditions were optimized using the statistical design of experiments (DOE). A Plackett–Burman (P–B) design was chosen to estimate the influence of five factors, such as resonance excitation voltage (EV), isolation time (IT), excitation time (ET), ion source temperature (IST) and electron energy (EE) on the analytical r…
Comparison of gas and liquid chromatography coupled to mass spectrometry for the residue analysis of pesticides in organges
2001
Liquid chromatography-mass spectrometry (LC-MS) with atmospheric pressure chemical ionization (APCI), and gas chromatography-mass spectrometry (GC-MS) with electron impact ionization (EI), are compared for the determination of eight pesticides in oranges. Seven of the selected pesticides, chlorpyriphos, chlorpyriphos-methyl, imazalil, α and β-endosulfan, endosulfan sulphate and dicofol, are commonly determined by GC whereas one, thiabendazole, can only be directly determined by LC. Primary ions [M-H]− or [M-Cl+O]− are obtained using LC-APCI-MS in negative ionization (NI) mode. In contrast, a high degree of fragmentation is reported with GC-MS. Both techniques were applied to oranges, which …
Determination of fungicide residues in fruits and vegetables by liquid chromatography–atmospheric pressure chemical ionization mass spectrometry
2002
Abstract A liquid chromatography (LC) method for the quantitative determination of five fungicide residues (dichloran, flutriafol, o -phenylphenol, prochloraz and tolclofos methyl) in oranges, lemons, bananas, peppers, chards and onions is described. The residues were extracted by matrix solid-phase dispersion (MSPD) using C 8 . Quantitative analysis was performed by isocratic LC coupled to quadrupole mass spectrometer using atmospheric pressure chemical ionization in the negative ionization mode. The limit of quantification was 0.01 mg kg −1 for flutriafol, o -phenylphenol and dichloran, and 0.1 mg kg −1 for prochloraz and tolclofos methyl. The MSPD method is also suitable for LC–UV analys…
Multiple-stage mass spectrometric analysis of six pesticides in oranges by liquid chromatography–atmospheric pressure chemical ionization–ion trap ma…
2004
Abstract Six pesticides were determined by liquid chromatography (LC) with positive ion (PI) atmospheric pressure chemical ionization quadrupole ion-trap tandem mass spectrometry (APCI–MS–MS). Ion fragmentation was studied by MS, MS 2 and MS 3 . Fragmentation of the pesticides produced ions formed by various losses from the side-chains and through heterocyclic ring opening, but without any common fragmentation pathway. Multiple reaction monitoring (MRM) of MS, MS 2 and MS 3 was used to identify and quantify the pesticides. The samples were extracted with ethyl acetate and dried over anhydrous sodium sulfate. Comparison of the three MS modes showed that MS 3 is slightly less sensitive but mu…
Determination of carbamate residues in fruits and vegetables by matrix solid-phase dispersion and liquid chromatography-mass spectrometry.
2000
Abstract Thirteen carbamates were analysed in orange, grape, onion and tomatoes by matrix solid-phase dispersion (MSPD) followed by liquid chromatography–mass spectrometry (LC–MS). Electrospray (ES) and atmospheric pressure chemical ionisation (APCI) were compared and both gave similar results in terms of sensitivity and structural information because at 20 V fragmentor voltages the fragmentation is minimal. The efficiency of different solid-phases (C18, C8, cyano, amine and phenyl) for the MSPD was compared. Mean recoveries using C8 varied from 64 to 106% with relative standard deviations of 5–15% in the concentration range of 0.01–10 mg kg−1. Matrix constituents did not interfere signific…
Analysis of organophosphorus pesticides in honeybee by liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry.
2001
Pesticides applied in extended agricultural fields may be controlled by means of bioindicators, such as honeybees, in which are the pesticides bioaccumulate. Liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (LC-APCI-MS) experiments with positive (PI) and negative (NI) ion modes were optimized for the analysis of 22 organophosphorus pesticides in honeybee samples. The extraction required 3 g of sample, which was extracted with acetone. The extract was purified with coagulating solution and reextracted with Cl(2)CH(2). Pesticides studied could be detected by both ionization modes except for parathion, parathion-methyl, and bromophos, which did not give signals …