Negative Electrospray Ionization (negative + electrospray_ionization)

Distribution by Scientific Domains

Terms modified by Negative Electrospray Ionization

  • negative electrospray ionization tandem mass spectrometry

  • Selected Abstracts

    Determination of S -phenylmercapturic acid in human urine using an automated sample extraction and fast liquid chromatography-tandem mass spectrometric method

    Yinghe Li
    Abstract S -phenylmercapturic acid is widely accepted as a specific biomarker for the evaluation of benzene exposure. Here, we describe a fast, specific and sensitive high-performance liquid achromatography coupled with tandem mass spectrometry (LC-MS/MS) method that has been developed and validated for the determination of S- phenylmercapturic acid in human urine. Isotope-labeled S- phenylmercapturic acid- d5 was used as internal standard to improve the method ruggedness. The fully automated solid-phase extraction method on a 96-well Oasis MAX (mix-mode anion exchange) plate was employed to clean up the urine samples before analysis. The rapid LC-MS/MS analysis of extracted samples was achieved on a Genesis C18 column with a run time of only 3 min. Negative electrospray ionization with multiple reaction monitoring (ESI-MRM) mode was used to detect S- phenylmercapturic acid (m/z 238 , 109) and S- phenylmercapturic acid - d5 (m/z 243 , 114). The method fulfils all the standard requirements of method validation. The calibration curve was linear within the concentration range 0.400,200 ng/mL. The method performed accurately and precisely in validation with <7.5% relative error and <6.5% relative standard deviation of quality control samples. The method efficacy was also verified by the analysis of urine samples from 12 smokers and 12 non-smokers. With the fully automated sample cleanup procedure and the fast LC-MS/MS analysis, a sample analysis throughput of 384 samples per day could be achieved. Copyright © 2006 John Wiley & Sons, Ltd. [source]

    High-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry for the determination of flocoumafen and brodifacoum in whole blood

    Mi-cong Jin
    Abstract A high-performance liquid chromatographic,tandem mass spectrometric (HPLC,MS,MS) assay was developed and validated to determine quantitatively flocoumafen and brodifacoum in whole blood using warfarin as an internal standard (IS). Liquid,liquid extraction, using ethyl acetate, was used to isolate flocoumafen, brodifacoum and the IS from the biological matrix. Detection was performed on a mass spectrometer by negative electrospray ionization (ESI) in multiple reaction monitoring (MRM) mode. The calibration curves were linear (r2 > 0.998) in the concentration range of 0.1,100.0 ng ml,1 with a lower limit of quantification of 0.05 ng ml,1 for flocoumafen, and 0.1 ng ml,1 for brodifacoum in whole blood. Intra-day and inter-day relative standard deviations (RSDs) were less than 8.0% and 10.8%, respectively. Recoveries of flocoumafen and brodifacoum ranged from 78.0% to 83.7%. This assay can be used to determine trace flocoumafen and brodifacoum in whole blood to investigate suspected poisoning of human and animals. Copyright © 2006 John Wiley & Sons, Ltd. [source]

    Tuning compounds for electrospray ionization/in-source collision-induced dissociation and mass spectra library searching

    Wolfgang Weinmann
    Abstract Tuning compounds for positive and negative electrospray ionization (ESI) were tested for the tuning of in-source collision-induced dissociation (ESI/CID) with three types of SCIEX API instruments (API 365, 2000 and 3000) in the single-quadrupole mode. The vacuum interfaces of these instruments differ slightly in geometry, but the principles of ionization and solvent evaporation by nebulizer and curtain gases, orifice and skimmer are identical. For comparison of in-source CID, breakdown curves of haloperidol, paracetamol, metronidazole and metamizole were acquired by increasing the orifice voltages. The API 2000 and 3000 required higher orifice voltages than did the API 365 to induce a similar degree of fragmentation of the protonated or deprotonated molecules to characteristic fragment ions. This increase of orifice voltage could be demonstrated with each of the four compounds tested by a shift of the maxima of the breakdown curves to higher orifice voltages. A procedure with three collision energy (CE) levels for drug identification with a mass spectra library set up with an API 365 therefore required an adjustment of the orifice voltages to higher values when being transferred to an API 2000 or API 3000. The corresponding orifice voltages for the three instruments were 20/50/80 V (API 365), 30/90/130 V (API 2000) and 40/80/120 V (API 3000). However, a change in orifice voltage of ±10 V (with the API 2000 and 3000) hardly influenced the fit values of a library search for each single CE level. For adjusting orifice voltages with different instruments, a tuning procedure with haloperidol and paracetamol is presented. With this tuning procedure an ESI/CID mass spectra library set up for API 365 and API 150 could also be used for drug identification with an API 2000 and an API 3000 with good library search results. Copyright © 2001 John Wiley & Sons, Ltd. [source]

    Phospholipids in liquid chromatography/mass spectrometry bioanalysis: comparison of three tandem mass spectrometric techniques for monitoring plasma phospholipids, the effect of mobile phase composition on phospholipids elution and the association of phospholipids with matrix effects

    Yuan-Qing Xia
    Because plasma phospholipids may cause matrix effects in bioanalytical liquid chromatography/tandem mass spectrometry (LC/MS/MS) methods, it is important to establish optimal mass spectrometric techniques to monitor the fate of phospholipids during method development and application. We evaluated three MS/MS techniques to monitor phospholipids using positive and negative electrospray ionization (ESI). The first technique is based on using positive precursor ion scan of m/z 184, positive neutral loss scan of 141 Da and negative precursor ion scan of m/z 153. The second technique is based on using class-specific positive and negative selected reaction monitoring (SRM) transitions to monitor class-representative phospholipids. The third technique, previously reported, utilizes in-source collision-induced dissociation (CID)-based positive SRM of m/z 184,,,184. We recommend the all-inclusive technique 1 for use in qualitative assessment of all classes of phospholipids and technique 2 for use in quantitative assessment of class-representative phospholipids. Secondly, we evaluated the elution behaviors of the plasma phospholipids under different reversed-phase mobile phase conditions. The phospholipid-eluting strength of a mobile phase was mainly dependent on the type and amount (%) of the organic eluent and the strength increased in the order of methanol, acetonitrile and isopropyl alcohol. Under the commonly used gradient and isocratic elution schemes in LC/MS/MS bioanalysis, not all the phospholipids are eluted off the column. Thirdly, we investigated the association between phospholipids and matrix effects in positive and negative ESI using basic, acidic and neutral analytes. While the phospholipids caused matrix effects in both positive and negative ESI, the extent of ionization suppression was analyte-dependent and was inversely related to the retention factor and broadness of the phospholipids peaks. The lysophospholipids which normally elute earlier in reversed-phase chromatography are more likely to cause matrix effects compared to the later-eluting phospholipids in spite of the larger concentrations of the latter in plasma. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Characterization and determination of chlorophacinone in plasma by ion chromatography coupled with ion trap electrospray ionization mass spectrometry

    Xiao-kun OuYang
    Abstract Plasmatic chlorophacinone is commonly measured with liquid chromatographic assay, which convenient but lacks sensitivity and selectivity and usually requires ion pair reagents to reduce the chromatographic tailed peak. In this paper, a novel method using eluent generator reagent-free ion chromatography coupled with electrospray ionization ion trap mass spectrometric detection for the determination of chlorophacinone in plasma has been developed. After samples were extracted with 10% (v/v) methanol in acetonitrile and cleaned by solid-phase extraction, chromatographic separation was performed on an IonPac® AS11 analytical column (250 × 4.0 mm) using 40.0 mmol/L KOH containing 10% (v/v) methanol as organic modifier. Quantification was performed by negative electrospray ionization in multiple reaction monitoring mode. The transition m/z 373 , 201 was for the quantification ion; the transitions m/z 373 , 172 and m/z 373 , 145, as well as the isotope ions m/z 375 and m/z 203, were for the qualitative ions. All the method parameters were validated. It was confirmed that this method can be used in clinical diagnosis and forensic toxicology. Copyright © 2008 John Wiley & Sons, Ltd. [source]