Electrospray negative ion mode

Figure 4.19. Fragmentation mechanism for GSH in electrospray negative ion mode.

Detector MS, PE Sciex API-Ill Plus quadrupole, electrospray, negative ion mode, electrospray interface - 3700 V, orifice - 62 V, nebulizer gas nitrogen at 50 psi, curtain gas nitrogen at 1.8 L/min, collision gas argon, collision offset energy 25 eV, m/z 313-118... 

Electrospray is the softest mass spectrometry ionization technique and electrospray spectra therefore usually consist solely of molecular ions. Electrospray is unique, however, in that if the analyte contains more than one site at which protonation (in the positive-ion mode) or deprotonation (in the negative-ion mode) may occur, a number of molecular ions with a range of charge states is usually observed. For low-molecular-weight materials (< 1000 Da), the number of sites... 

Electrospray (Turbo lonSpray), negative ion mode MS/MS with multiple reaction monitoring (MRM) -4500 V... 

L. Konermann and D. J. Douglas. Unfolding of Proteins Monitored by Electrospray Ionization Mass Spectrometry A Comparison of Positive and Negative Ion Modes. J. Am. Soc. Mass Spectrom., 9(1998) 1248-1254. 

Detection of M2D-C3-0-(E0)n-CH3 was possible by both positive ion mode atmospheric pressure chemical ionisation (APCI) and electrospray ionisation (ESI) MS methods, with good response down to absolute injections of 0.1 ng. However, ionisation in the negative ion mode was negligible at all concentrations analysed, as the polyether-modified structure has no sites capable of adducting with anions, nor has it any moieties capable of cleavage to yield anionic species. 

Owing to the anionic character of LAS, an electrospray ionisation (ESI) interface operated in negative ion mode is particularly attractive for the mass spectrometric detection of this surfactant type. Consequently, a great part of the atmospheric pressure ionisation-mass spectrometry (API-MS) work on LAS is devoted to the application of (— )-ESI-MS. 

Fig. 9. Precursor ion scan on an electrospray triple quadrupole mass spectrometer. From all the peptides present of the digested protein only those that are phosphorylated are detected in a precursor ion scan for the phosphate ion (P03, mass 79 Da) in negative ion mode. From the TPX protein three phosphorylated peptides could be detected Ml, AQLTM PSTPTVLK M2, LSETSVNTEQNSK and M3, VQPVQTTPSKDDVSNSATHVC DVK. M, Oxidized methionine C, carbamidomethylated cysteine.

Lee KC, Chan W, Liang Z, Liu N, Zhao Z, Lee AW, Cai Z (2008) Rapid screening method for intact glucosinolates in Chinese medicinal herbs by using liquid chromatography coupled with electrospray ionization ion trap mass spectrometry in negative ion mode. Rapid Commun Mass Spectrom 22 2825-2834... 

At the end of the column the eluent is split, and the sample is introduced into the electrospray source of the mass spectrometer at a rate of about 20 pl/min. Spectrometer voltages are optimised to obtain the maximum signal for each BA. Spectra are acquired in negative ion mode. 

Using electrospray ionization mass spectrometry in both positive and negative ion modes, the on-line scanning of the Morita-Baylis-Hillman reaction in the presence of imidazolium ionic liquids has been investigated. The interception of several supramolecular species indicated that ionic liquids co-catalyse the reactions by activating the aldehyde toward nucleophilic enolate attack and by stabilizing the zwitterionic species that act as the main intermediates.175... 

A. Pfenninger, M. Karas, B. Finke, and B. Stahl, Structural analysis of underivatized neutral human milk oligosaccharides in the negative ion mode by nano-electrospray MSn (Part 2 Application to isomeric mixtures), J. Am. Soc. Mass Spectrom., 13 (2002) 1341-1348. 

The synthesis of phosphopeptides is typically confirmed mass spectrometri-cally using either a MALDI (matrix-assisted laser desorption/ionizafion) or an ESI (electrospray ionization) source, and the peptide purity is determined by reversed-phase chromatography coupled to an UV detector (Figs. 1 and 2B). Whenever possible, phosphopeptide analyses should be complimented by mass spectra recorded in negative ion mode. For most biochemical applications it is necessary to purify the peptides by HPLC techniques (Fig. 2A). 

LC-MS/MS System Used and Analytical Conditions An Agilent Technologies (Palo Alto, CA, USA) 1100 series LC-system was used, connected to an API 4000 triple quadrupole mass spectrometer (Applied Biosystems MDS Sciex, Concord, ON, Canada). The mass spectrometer was equipped with an Electrospray ionization source (negative ion mode). 

Ion source Electrospray, negative mode Mass transitions (optimized precursor and product ion mass to charge ratio) in negative ion mode Hyperforin 535 -> 383 m/z The instrument parameters have been optimized for the analysis of hyperforin. Both quadrupoles (Q1 and Q3) were operated in unit resolution. 

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