Liquid chromatography/atmospheric pressure ionization mass spectrometry with post-column liquid mixing for the efficient determination of partially oxidized polycyclic aromatic hydrocarbons
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Atmospheric-pressure chemical ionization
Abstract Clenbuterol is a β‐agonist drug used illegally as a growth stimulant in meat‐producing animals and human athletes. The analysis of clenbuterol in spiked human plasma was performed using on‐line liquid chromatography/atmospheric‐pressure chemical‐ionization mass spectrometry (LC/APCI‐MS) using a conventional bore LC column (flow rate = 1.0 mL/min). At low sampling cone voltages, the mass spectrum was predominantly the [M + H] + ion but diagnostic fragment ions were formed upon incremental increases in sampling cone voltage. The detection limit (signal‐to‐noise ratio of 3) using selected‐ion monitoring of the [M + H] + ion was 0.1 ng on‐column (l0 ppb). This is a 50‐fold better sensitivity of detection than that previously reported for an on‐line thermospray LC/MS method. The extraction procedures were not optimized for maximum sensitivity and the lack of interferences suggests that much lower detection limits for clenbuterol in plasma are attainable.
Atmospheric-pressure chemical ionization
Clenbuterol
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Atmospheric-pressure chemical ionization
Desorption electrospray ionization
Extractive electrospray ionization
Ambient ionization
Capillary electrophoresis–mass spectrometry
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High-performance liquid chromatography with atmospheric pressure chemical ionization mass spectrometry (APCI-MS) in the negative-ion mode has been succesfully used for qualitative and quantitative determination of fifteen phenolic compounds found in olive mill wastewater. APCI gives information about both the molecular weight of these molecules and about their structure, showing consistent collision-induced dissociation pathways, which have been elucidated to give detailed information about the structure of the fragments. Quantitative analysis, using p-bromophenol as an internal standard, was carried out using calibration graphs for injections in the 0.01–1000 ng range, working both in scanning and selected-ion monitoring data aquisition modes, resulting in correlation coefficients higher than 0.98 for all compounds.
Atmospheric-pressure chemical ionization
Collision-induced dissociation
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A novel chemical ionization source for organic mass spectrometry is introduced. This new source uses a glow discharge in the flowing afterglow mode for the generation of excited species and ions. The direct-current gas discharge is operated in helium at atmospheric pressure; typical operating voltages and currents are around 500 V and 25 mA, respectively. The species generated by this atmospheric pressure glow discharge are mixed with ambient air to generate reagent ions (mostly ionized water clusters and NO+), which are then used for the ionization of gaseous organic compounds. A wide variety of substances, both polar and nonpolar, can be ionized. The resulting mass spectra generally show the parent molecular ion (M+ or MH+) with little or no fragmentation. Proton transfer from ionized water clusters has been identified as the main ionization pathway. However, the presence of radical molecular ions (M+) for some compounds indicates that other ionization mechanisms are also involved. The analytical capabilities of this source were evaluated with a time-of-flight mass spectrometer, and preliminary characterization shows very good stability, linearity, and sensitivity. Limits of detection in the single to tens of femtomole range are reported for selected compounds.
Atmospheric-pressure chemical ionization
Ambient ionization
Glow discharge
Atmospheric-pressure laser ionization
Discharge ionization detector
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Liquid chromatography/mass spectrometry (LC/MS) operating conditio na nd the sample preparation method were developed and fully validated according to the guidelines issued by Internal Conference on Harmonization (ICH) for the determination of (R )�3�chlorostyrene oxide (RCSO) present in bulk chemicals. RCSO is the raw material of a certain promising medical chemical. The chromatographic separation of RCSO and bulk chemical was achieved using a mixture of methanol and acetate buffer (3:2) as the mobile phase. Mass spectrometric analysis was performed by atmospheric pressure chemical ionization (APCI )m ode with positive ion detection. Single ion monitoring (SIM) scan
Atmospheric-pressure chemical ionization
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A tube plasma ionization (TPI) open-air source for gas chromatography-mass spectrometry (GC-MS) was developed. This source is based on an inverse low temperature plasma configuration where the pin inner electrode is applying the high voltage and the grounded electrode is the housing itself. The ionization possibilities were tested by using an EPA mix of priority contaminants, showing that 68% of the analytes could undergo both proton-transfer and charge-exchange reactions. The potential of using different discharge gases (He and Ar) to ionize the analytes and auxiliary gases (He, N2, O2, and synthetic air) to transport the ions toward the MS was carefully investigated. Additionally, the addition of water was also tested to show the different ionization trends in the TPI source. Finally, the ionization by TPI under both dry and wet conditions was compared with other gas-phase atmospheric pressure ionization sources showing TPI could ionize a wider range of compounds (97%) than atmospheric pressure chemical ionization (APCI, 95%) and atmospheric pressure photoionization (APPI, 87%). Besides, the detection capability of TPI was better than APCI and APPI, achieving instrumental limits of detection down to 3 fg on column, which demonstrates the great potential of this ionization source for GC-MS determinations.
Atmospheric-pressure chemical ionization
Ambient ionization
Atmospheric-pressure laser ionization
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A high-performance liquid chromatograph with mass spectrum detection (HPLC-MS/APCI) method has been established for simultaneous determination of ten major bioactive components of Naodesheng injection including safflor yellow A, puerarin, daidzein, ginsenosides (Rg1, Rg2, Rb1, Rd, Re, Rh1), and notoginsenoside R1. The separations were carried out with a Luna C18 column (5 μm, 150×4.6 mm, Phenomenex, U.S.A.) with a stepwise gradient elution of the mobile phase consisting of water (0.1% of formic acid, v/v)–methanol (0 min, 70 : 30; 8 min, 30 : 70; 20 min, 10 : 90) at a flow-rate of 0.8 ml/min. The proposed method was applied to analyze five various Naodesheng injections and produced data with acceptable linearity, repeatability, precision and accuracy having lower limits of quantitation (LLOQs) of 0.02—0.2 μg. The calibration curves were linear in respective range for all compounds, all of them with coefficients of determination above 0.9900. The intraday precessions were less than 5.0%. The proposed method is accurate, sensitive and simple, a useful alternative for routine analysis in the quality control of Traditional Chinese Medicine.
Atmospheric-pressure chemical ionization
Thermospray
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The ion source is the component of a mass spectrometer where ionization takes place. Some ion sources, such as electron ionization (EI) and chemical ionization (CI) impose the requirement that the samples are in the gaseous form even before they are introduced to the ion source chamber. This chapter describes the most common ionization techniques, including EI, CI, atmospheric pressure chemical ionization (APCI), electrospray ionization (ESI), desorption/ionization (DI), as well as the recently developed ion sources operating at atmospheric pressure. The time spent on ionization contributes to temporal resolution of time-resolved mass spectrometry (TRMS). This intrinsic dead time of the analytical procedure is discussed for different ionization technique. Atmospheric pressure photoionization (APPI) complements APCI and ESI in its functionality and application scope. It can be used to ionize analytes with relatively low polarity, which is difficult to be ionized using other atmospheric pressure ionization techniques.
Atmospheric-pressure chemical ionization
Desorption electrospray ionization
Ambient ionization
Atmospheric-pressure laser ionization
DART ion source
Thermal ionization
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A total of 15 standard compounds with structures similar to those normally found in crude oils were analyzed using an ultrahigh-resolution and high-accuracy Fourier transform ion cyclotron resonance (7.2 T LTQ FT Ultra, Thermo Fisher, Bremen, Germany) mass spectrometer. Four different ionization techniques were used: electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), atmospheric pressure photoionization (APPI), and a novel technique that couples APCI and APPI, herein termed atmospheric pressure photo- and chemical ionization (APPCI). Relationships between chemical structures and ionization efficiencies were established for these techniques, which operate via different ionization mechanisms. The unsaturation level and position of the double bond were shown to be key factors on ionization efficiency for all ionization techniques. Comparisons between molecules with similar backbones but with different heteroatoms were also made. For the whole mixture, APPI showed the highest sensitivity for the positive ion mode and ESI showed the highest sensitivity for the negative ion mode. APPCI was found to be the most comprehensive ionization technique, whereas as expected, ESI preferentially ionized the most polar compounds. APPCI produced, however, more than one ionic species per molecule, a disadvantage in terms of data complexity. Such "splitting" was observed for APPI and APCI. Ions with the same molecular formula formed from different molecules were also detected by APPCI, producing composite abundances that would mislead chemical and geochemical conclusions based on petroleomic approaches. We suggest that, although less comprehensive, ESI is overall the most suitable ionization technique for petroleomic studies.
Atmospheric-pressure chemical ionization
Ambient ionization
Desorption electrospray ionization
Atmospheric-pressure laser ionization
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Atmospheric-pressure chemical ionization
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