Ion Trap MS

The ion trap mass analyzer is similar to the quadrupole but with the important distinction that it can isolate and trap ions in an electrical field. Notably, the ion trap differs significantly from quadrupoles in design and operation in that triple quadrupoles perform tandem mass analysis on ions as they pass through an analyzer ion traps are capable of isolating and retaining specific ions for fragmentation upon collision with an inert gas in the same cell. An ion trap is about the size of a tennis ball and consists of a donut-shaped electrode and two perforated disk-like end-cap electrodes. 

The mass-selective instability mode of operation permits the selection and trapping of all ions created over a specified period with subsequent ejection to the detector.26 Ions with different m/z values can be confined within the ion trap and scanned singly by application of voltages that destabilize the orbits of the ions and eject them to the detector. Ion trap instruments interface readily with liquid chromatography, ESI,15 and MALDI.27 The motions of the ions and the dampening gas (e.g., helium) concentrate around the middle of the ion trap, thereby diminishing ion loss through collisions with electrodes. 

Ion traps are favored for proteomics studies because of their ability to perform multistage mass analysis (MSn), thereby increasing the structural information obtained from molecules. Ion traps, however, do not provide information for ions that have lower mass-to-charge values (the one-third rule). Additionally, the sensitivity of ion traps can also be limiting because only about 50% of the ions within a trap are ejected to the detector. Ion traps are also subject to a space charging phenomenon that may occur when the concentration of ions in the trap is high and produces ion repulsion within the trap. Nevertheless, the versatility and robustness of ion trap MS underlies its popularity for several proteomics-related applications. 

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A further extension of the DFG S19 method was achieved when polar analytes and those unsuitable for GC were determined by LC/MS or more preferably by liquid chromatography/tandem mass spectrometry (LC/MS/MS). Triple-quadrupole MS/MS and ion trap MS" have become more affordable and acceptable in the recent past. These techniques provide multiple analyte methods by employing modes such as time segments, scan events or multiple injections. By improving the selectivity and sensitivity of detection after HPLC separation, the DFG S19 extraction and cleanup scheme can be applied to polar or high molecular weight analytes, and cleanup steps such as Si02 fractionation or even GPC become unnecessary. 

Ion trap MS is particularly suited for chemical structure elucidation, as it allows for simultaneous ion storage, ion activation and fragmentation, and product ion analysis. The fragmentation pathway of selected ions and the fragmentation products provide information on the molecular structure. Compared with triple-quadrupole and especially with sector instruments, the ion trap instrument provides more efficient conversion of precursor ion into product ions. However, the CID process via resonance excitation, although quite efficient in terms of conversion yield, generally results in only one (major) product ion in the product-ion mass spectrum. MS/MS with a quadrupole ion trap offers a number of advantages ... 

Sludge E2, EE, El, MES Solvent extraction, GPC, silica gel column, derivatization with MSTFA GC-ion-trap MS/MS LOQ 2-4 [45]... 

With the commercially available MS—MS instruments in the 1990s, MS-MS helped to overcome these identification obstacles via CID in MS—MS mode or via ion trap in MS mode. In parallel, the applicability of MS—MS and MS by CID on tandem or ion trap MS become much easier and more informative with new MS spectrometric hardware, which is supported by the implemented improved computer systems. This combination of high-end data systems with more automated MS-MS and MS instruments facilitates the application of MS-MS and leads to a tremendous increase in the information output. 

Lately, electrospray ionisation technique (ESI-MS) which is compatible with RP-HPLC has been routinely used. This allows labile molecules to be studied intact. Sample molecules are simultaneously nebulised and ionised at atmospheric pressure in the presence of several thousand volts. The resulting ions can be multi-protonated (multiply charged) and relatively stable. This mode of ionisation has recently been used in the development of RP-HPLC coupled with positive ion ESI-MS and ion-trap MS protocols for the identification and... 

Interference occurs when compounds co-elute with the analytes and are not detected directly by a specific detector. The effect is to create negative peaks or an erratic response for the analyte. This problem can be identified by using a non-specific detector such as an ion trap MS detector, an MS in the electron impact ionization mode, or a flame ionization GC detector. 

Wang, Y. Schubert, M. Ingendoh, A. Franzen, J. Analysis of Non-Covalent Protein Complexes Up to 290 KDa Using ESI and Ion Trap-MS. Rapid Common. Mass Spectrom. 2000,14, 12-17. 

Levine, L.H. Garland, J.L. Johnson, J.V. HPLC/ESI-Quadrupole Ion Trap-MS for Characterization and Direct Quantification of Amphoteric and Nonionic Surfactants in Aqueous Samples. Anal. Chem. 2002, 74, 2064-2071. 

Weiskopf, A.S. Vouros, P. Harvey, D.J. ESI-Ion Trap-MS for Stractural Analysis of Complex iV-Linked Glycoprotein Oligosaccharides. Anal. Chem. 1998, 70, 4441-4447. 

Air Solid Phase Microextraction transfer to GC via thermal desorption of fiber. GC/ion trap MS 2 ppb (v/v) 6% RSD No data Chai and Pawliszyn 1995... 

Solid-phase microextraction (SPME) for preconcentration, followed by GC/ Ion Trap MS, was used for trace analysis of explosives and their metabolites in seawater [9]. NICI was used with methane as reagent gas. Compounds of interest included RDX, TNT and two of its metabofrtes 2-amino-4,6-dinitrotoluene (2ADNT) and 4-amino-2,6-dinitrotoluene (4ADNT). Although the instrument sensitivity was in low-ppb range, the detection limits for SPME with GC/ITMS... 

With quadrupole CID all fragments are recorded in one experiment, while in the case of the 3D ion trap MS, MS and experiments are required to ob-... 

Separation and detection techniques for antibacterials in food mainly focus on the use of LC coupled to MS or tandem MS. Nevertheless, recent studies have suggested capillary electrophoresis coupled to laser-induced fluorescence (LIE) as a way of improving sensitivity [49], HRLC coupled to microTOF-ESI-MS as a highly selective, sensitive, and quick screening method for 100 veterinary drugs in fish, meat, and egg samples [195], and nanoscale LC coupled to UV or ion trap MS, with LODs in the range 0.01-0.51 pg/L (nanoLC-MS) and the possibility that even lower limits could be achieved by using triple quadrupole MS [59]. 

HPLC-LTQ/FTMS N-Unked glycosylation structures in human plasma HPLC-Ion Trap MS Proteins expressing differences among isolates of Meloidogyne spp. HPLC-MALDI Monosaccharide anhydride levoglucosan, galactosan, and mannosan in the... 

Perbellini, L., Gottardo, R., Caprini, A., Bortolotti, F., Mariotto, S., and Tagliaro, F., Determination of alpha-bisabolol in human blood by micro-HPLC-ion trap MS and head space-GC-MS methods. Journal of Chromatography. B, Analytical Technologies in the Biomedical and Life Sciences 812(1-2), 373-377, 2004. 

For the determination of organotin compounds (tributyltin, triphenyltin, triethyltin, and tetra-ethyltin) a MAE is proposed before the normal phase (NP) HPLC/UV analysis [35], In organotin and arsenic speciation studies, hydride generation is the most popular derivatization method, combined with atomic absorption and fluorescence spectroscopy or ICP techniques [25,36], Both atmospheric pressure chemical ionization (APCI)-MS and electrospray ionization ESI-MS are employed in the determination of butyltin, phenyltin, triphenyltin, and tributyltin in waters and sediments [37], A micro LC/ESI-ion trap MS method has been recently chosen as the official EPA (Environmental Protection Agency) method (8323) [38] it permits the determination of mono-, di-, and tri- butyltin, and mono-, di-, and tri-phenyltin at concentration levels of a subnanogram per liter and has been successfully applied in the analysis of freshwaters and fish [39], Tributyltin in waters has been also quantified through an automated sensitive SPME LC/ESI-MS method [40],... 

Favretto et al. [33] proposed a procedure for the analysis of BUP and nor BUP based on RP-HPLC conpled with ion trap MS nsing an ESI ion source. The use of the ion trap allowed to obtain intense prodnct ions nnder MS-MS conditions, thus achieving better selectivity of detection with respect to LC-ESI-MS-MS methods with triple qnadrupoles where effective fragmentation in the collision cell was fonnd difficnlt to obtain. However, this method does not inclnde phase II metabolites of BUP, which can be only indirectly determined after enzymatic hydrolysis. 

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