A new coupling of electrochemistry with mass spectrometry (MS) using probe electrospray ionization (PESI) is presented. Due to the high salt tolerance of PESI, the detection of electrochemical reaction products in room‐temperature ionic liquids (RTILs) is realized for the first time. Furthermore, PESI‐MS allows the analysis of electrochemical reaction products on different or multiple electrode surfaces. In addition, peptides and proteins fractionated through isoelectric focusing (IEF) in the presence of an external electric field can also be directly analyzed by using PESI‐MS, suggesting a new and rapid characterization means for the IEF technique. This study reveals the versatility of EC/PESI‐MS, which could have an impact in electrochemistry and bioanalysis fields. 相似文献
We report a new mass spectrometric method for detecting electrogenerated intermediates. This approach is based on simultaneous activation of electrospray ionization and redox reaction on a wireless bipolar ultramicroelectrode, which is fabricated in the tip of a quartz nanopipette. The hollow structure of the ultramicroelectrode permits rapid transferring the transient species from electrode–electrolyte interfaces into the gas phase for mass spectrometric identification on the time scale of microseconds. The long-sought fleeting intermediates including TPrA.+, whose lifetime in solution is only 200 μs, and catecholamine o-semiquinone radicals, the second-order rate constant of which is typically 109 m −1 s−1, were successfully identified, helping clarify the previously hidden reaction pathways. Accordingly, our method may have wide applicability in exploring the dynamics of many electrochemical reactions, especially their ultrafast initial steps. 相似文献
A high throughput screening system involving a linear ion trap (LTQ) analyzer, a house-made platform and a desorption electrospray ionization (DESI) source was established to screen ligands with a high affinity for proteins with anion-binding sites. The complexes were analyzed after incubation, ultrafiltration, washing, and displacement. A new anionic region inhibited dissociation (ARID) mechanism that was suitable for a protein with anion-binding site was proposed. We utilized the differences in detectable dissociation of protein–ligand complexes, combined with displacement experiments, to distinguish free ligands displaced from anion-binding sites from liberated ligands dissociated from nonspecific interactions. The method was validated by α1-acid glycoprotein (AGP) and (R), (S)-amlodipine. Site-specific enantioselectivity shown in our experiments was consistent with earlier studies. Obtaining all of the qualitative information of 15*3 samples in 2.3 min indicates that the analysis process is no longer the time-limiting step in the initial stage of drug discovery. Quantitative information verified that our method was at least a semiquantitative method.
We report a new mass spectrometric method for detecting electrogenerated intermediates. This approach is based on simultaneous activation of electrospray ionization and redox reaction on a wireless bipolar ultramicroelectrode, which is fabricated in the tip of a quartz nanopipette. The hollow structure of the ultramicroelectrode permits rapid transferring the transient species from electrode–electrolyte interfaces into the gas phase for mass spectrometric identification on the time scale of microseconds. The long‐sought fleeting intermediates including TPrA.+, whose lifetime in solution is only 200 μs, and catecholamine o‐semiquinone radicals, the second‐order rate constant of which is typically 109 m ?1 s?1, were successfully identified, helping clarify the previously hidden reaction pathways. Accordingly, our method may have wide applicability in exploring the dynamics of many electrochemical reactions, especially their ultrafast initial steps. 相似文献
A liquid chromatography/mass spectrometry (LC/MS) method using desorption electrospray ionization (DESI) as a versatile interface has been established, which allows a wide range of elution flow rates, online derivatization via reactive DESI and further combination with electrochemistry. 相似文献
We report the development and validation of a high-performance liquid-chromatographic–tandem mass spectrometric method for determination of artemether (ARM) and its active metabolite dihydroartemisinin (DHA) in human plasma; artemisinin was used as internal standard (IS). Chromatographic separation was performed on a 150 mm × 4.6 mm i.d., 5 μm particle, C18 column coupled with a 4.0 mm × 3.0 mm i.d., 5 μm particle, C18 guard column. The mobile phase was acetonitrile–0.1% formic acid solution, 80:20 (v/v), at a flow-rate of 1 mL min?1. An atmospheric-pressure chemical-ionization (APCI) interface was used to produce sample ions, and positive ions were quantified by using the MS detector in selected-reaction-monitoring mode, using the reaction m/z 221 to 163 for determination of ARM and DHA and the reaction m/z 283 to 219 for determination of the IS. Plasma samples were prepared by extraction with methyl t-butyl ether, evaporation of the extract to dryness, and reconstitution of the residue with mobile phase. Extraction recovery for ARM and DHA ranged from 74.74 to 99.39%. High specificity and a limit of quantification of 5 ng mL?1 were achieved for ARM and DHA. Linearity was confirmed over the concentration range 5–500 ng mL?1; the correlation coefficients (R) were >0.99. The relative standard deviation for intra-day and inter-day assay of both compounds was <9.60% and inaccuracy was within ±10.81%. Stock solutions were stable at 4 °C for at least 720 h. Processed extracts were stable at room temperature for at least 24 h and QC samples were stable during three freeze–thaw cycles. In spiked human plasma under ambient conditions ARM was stable for at least 8 h whereas DHA was stable for 2 h only. 相似文献
Mass 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.
High-performance liquid chromatography coupled with tandem mass spectrometry has been used for sensitive and specific quantitative analysis of norethisterone (NE) in human serum. NE and the internal standard fentanil were isolated by solid-phase extraction. Chromatographic separation was achieved on a 4.6 mm × 50 mm, 5-μm particle, C18 column. The mobile phase was 70:30 (v/v) methanol–0.5% aqueous formic acid. NE and the internal standard were detected by multiple-reaction monitoring of precursor/product ion combinations at m/z 299.4/231.2 and 377.1/188.1, respectively; an atmospheric-pressure-photoionization source was used in positive-ion mode. Linearity was established in the concentration range 0.2–49.24 ng mL?1 and the lowest limit of quantification was 0.2 ng mL?1. Recovery of NE ranged from 92.54 to 102.74% and relative standard deviations were <15%. The method was used for a pharmacokinetic study of NE in healthy postmenopausal Chinese female volunteers. 相似文献
A comprehensive analytical method based on LC coupled with ultraviolet–visible spectrometric detection and tandem mass spectrometry has been developed for the determination of sixteen carcinogenic and allergenic dyestuffs in toys. Various toy samples, including textiles, leathers, woods, paper, aqueous liquids, solid toy materials such as crayons, modeling or play clay, balloons and temporary tattoos were ultrasonically extracted with ethanol. Quantitative analysis was carried out after chromatographic separation with a mobile phase of acetonitrile-tetrahydrofuran-citrate buffered tetrabutylammonium hydroxide mixture under gradient elution. The mean recoveries at three spiked levels were between 88.6 and 104.7, with the relative standard deviations from 1.6 to 6.7%. The intra-day reproducibility ranged from 1.7 to 3.9% and inter-day reproducibility ranged from 3.0 to 5.8%. The identities of the dyestuffs were further verified by LC-tandem mass spectrometry. The method was successfully applied to the investigation of different toy components. 相似文献
A source that couples the desorption ionization by charge exchange (DICE) and desorption electrospray ionization (DESI) techniques
together was demonstrated to broaden the range of compounds that can be analyzed in a single mass spectrometric experiment
under ambient conditions. A tee union was used to mix the spray reagents into a partially immiscible blend before this mixture
was passed through a conventional electrospray (ES) probe capillary. Using this technique, compounds that are ionized more
efficiently by the DICE method and those that are ionized better with the DESI procedure could be analyzed simultaneously.
For example, hydroquinone, which is not detected when subjected to DESI-MS in the positive-ion generation mode, or the sodium
adduct of guaifenesin, which is not detected when examined by DICE-MS, could both be detected in one experiment when the two
techniques were combined. The combined technique was able to generate the molecular ion, proton and metal adduct from the
same compound. When coupled to a tandem mass spectrometer, the combined source enabled the generation of product ion spectra
from the molecular ion and the [M + H]+ or [M + metal]+ ions of the same compound without the need to physically change the source from DICE to DESI. The ability to record CID spectra
of both the molecular ion and adduct ions in a single mass spectrometric experiment adds a new dimension to the array of mass
spectrometric methods available for structural studies. 相似文献
Fully integrated : Mass spectrometry has been integrated into a detection scheme for microdroplets that are created within microfluidic channels (see picture, scale bar 200 μm). This technique allows droplets to be identified based on the compounds they contain, and combines fluorescence screening with MS analysis. These experiments indicate how similar approaches can be applied to the ambitious goals of on‐chip protein evolution and chemical synthesis.
