Quadrupole mass spectrometers, triple

Table 2. Scan Functions for a Triple Quadrupole Mass Spectrometer...

Figure 3.8 Schematic of a triple quadrupole mass spectrometer.

Table 5.21 Intra-assay precision and accuracy of theLC-MS-MS determination of Idoxifene using a triple-quadrupole mass spectrometer. Reprinted from J. Chromatogr., B, 757, Comparison between liquid chromatography-time-of-flight mass spectrometry and selected-reaction monitoring liquid chromatography-mass spectrometry for quantitative determination of Idoxifene in human plasma , Zhang, H. and Henion, J., 151-159, Copyright (2001), with permission from Elsevier Science...

A triple-quadrupole mass spectrometer with an electrospray interface is recommended for achieving the best sensitivity and selectivity in the quantitative determination of sulfonylurea herbicides. Ion trap mass spectrometers may also be used, but reduced sensitivity may be observed, in addition to more severe matrix suppression due to the increased need for sample concentration or to the space charge effect. Also, we have observed that two parent to daughter transitions cannot be obtained for some of the sulfonylurea compounds when ion traps are used in the MS/MS mode. Most electrospray LC/MS and LC/MS/MS analyses of sulfonylureas have been done in the positive ion mode with acidic HPLC mobile phases. The formation of (M - - H)+ ions in solution and in the gas phase under these conditions is favorable, and fragmentation or formation of undesirable adducts can easily be minimized. Owing to the acid-base nature of these molecules, negative ionization can also be used, with the formation of (M - H) ions at mobile phase pH values of approximately 5-7, but the sensitivity is often reduced as compared with the positive ion mode. 

For HPLC/MS/MS analysis, a triple-quadrupole mass spectrometer with an electrospray interface is recommended for achieving the best sensitivity and speciflcity in the quantitative determination of oxime carbamates and their metabolites. This allows... 

Currently, HPLC/fiuorescence is still the most common technique for the determination of residues of oxime carbamates. With the introduction of ESI and APCI MS interfaces, HPLC/MS analysis for oxime carbamates in various sample matrices has become widespread. However, for a rapid, sensitive, and specific analysis of biological and environmental samples, HPLC/MS/MS is preferred to HPLC/MS and HPLC/fiuorescence. With time, improved and affordable triple-quadrupole mass spectrometers will be available in more analytical laboratories. With stricter regulatory requirements, e.g., highly specific and conclusive methods with lower LOQ, HPLC/MS/MS will be a method of choice for oxime carbamates and their metabolites. 

Reversed-phase high-performance liquid chromatography (HPLC) column 50 mm x 3.2-mm i.d. with Kromasil 5- um Gig packing High-performance liquid chromatograph coupled to a triple-quadrupole mass spectrometer with an atmospheric pressure chemical ionization (APCI) source Gel permeation chromatograph with a 60 mm x 25-mm i.d. column packed with Bio-Beads SX-3 (50-g)... 

Inject an aliquot of the sample solution into theLC/MS/MS system. An HP1050 HPLC system coupled to a Perkin-Elmer API III triple-quadrupole mass spectrometer has been found to be suitable for this analysis. 

Confirmatory system Agilent Series 1100 liquid chromatograph Eclipse XDB Cig HPLC columu, 150 x 4.0-mm i.d., 3.5- im particle size MicroMass Quattro II triple-quadrupole mass spectrometer using an electrospray ionization (ESI) interface... 

B. HPLC operating conditions for confirmatory analysis on the Quattro II triple-quadrupole mass spectrometer... 

The results thus show that ammonia DCI-MS/MS using a triple quadrupole mass spectrometer is a convenient method for the detection of additives in PE samples. The softness and selectivity provided by ammonia DCI in combination with the specificity provided by CID, demonstrate great potential for identification of additives directly from PE extracts. The utility of DCI in the quantitative analysis of additives has still to be explored. DCI-MS/MS (B/E) with high collision... 

Selection of a suitable ionisation method is important in the success of mixture analysis by MS/MS, as clearly shown by Chen and Her [23]. Ideally, only molecular ions should be produced for each of the compounds in the mixture. For this reason, the softest ionisation technique is often the best choice in the analysis of mixtures with MS/MS. In addition to softness , selectivity is an important factor in the selection of the ionisation technique. In polymer/additive analysis it is better to choose an ionisation technique which responds preferentially to the analytes over the matrix, because the polymer extract often consists of additives as well as a low-MW polymer matrix (oligomers). Few other reports deal with direct tandem MS analysis of extracts of polymer samples [229,231,232], DCI-MS/MS (B/E linked scan with CID) was used for direct analysis of polymer extracts and solids [69]. In comparison with FAB-MS, much less fragmentation was observed with DCI using NH3 as a reagent gas. The softness and lack of matrix effect make ammonia DCI a better ionisation technique than FAB for the analysis of additives directly from the extracts. Most likely due to higher collision energy, product ion mass spectra acquired with a double-focusing mass spectrometer provided more structural information than the spectra obtained with a triple quadrupole mass spectrometer. 

FTIR in multiply hyphenated systems may be either off-line (with on-line collection of peaks) [666,667] or directly on-line [668,669]. Off-line techniques may be essential for minor components in a mixture, where long analysis times are required for FT-based techniques (NMR, IR), or where careful optimisation of the response is needed. In an early study a prototype configuration comprised SEC, a triple quadrupole mass spectrometer, off-line evaporative FTIR with splitting after UV detection see Scheme 7.12c [667]. Off-line IR spectroscopy (LC Transform ) provides good-quality spectra with no interferences from the mobile phase and the potential for very high sensitivity. Advanced approaches consist of an HPLC system incorporating a UV diode array, FTIR (using an ATR flow-cell to obtain on-flow IR spectra), NMR and ToF-MS. 

Figeys, D. Aebersold, R. High sensitivity identification of proteins by electrospray ionization tandem mass spectrometry inital comparison between an ion trap mass spectrometer and a triple quadrupole mass spectrometer. Electrophoresis 1997,18, 360-368. 

It is evident from the data in Figure 3, that maximum gas-phase ion intensities for a given analyte ion are obtained with 10-4 to 10-3 mol/L analyte in the solution. The 3 x 106 ion counts/s observed at such concentrations are intensities after mass analysis at low resolution where the gas was admitted through a 100 pm orifice into a vacuum chamber which contains a triple quadrupole mass spectrometer.51... 

Apparatus, developed in this laboratory for two types of thermochemical measurements—(a) gas-phase ion molecule equilibria and (b) collision-induced dissociation (CID) threshold measurements—will be described. For both purposes, a triple quadrupole mass spectrometer is used. It is only the front end modifications that provide the conditions for (a) or (b). 

Multiple mass analyzers exist that can perform tandem mass spectrometry. Some use a tandem-in-space configuration, such as the triple quadrupole mass analyzers illustrated (Fig.3.9). Others use a tandem-in-time configuration and include instruments such as ion-traps (ITMS) and Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS or FTMS). A triple quadrupole mass spectrometer can only perform the tandem process once for an isolated precursor ion (e.g., MS/MS), but trapping or tandem-in-time instruments can perform repetitive tandem mass spectrometry (MS ), thus adding n 1 degrees of structural characterization and elucidation. When an ion-trap is combined with HPLC and photodiode array detection, the net result is a profiling tool that is a powerful tool for both metabolite profiling and metabolite identification. 

One of the best tools for metabolite profiling is the hybrid QTRAP MS/MS system (Applied Biosystems).119-121 While the hybrid QTRAP MS/MS was initially considered a premier tool for metabolite identification, it has more recently been seen as a tool for quantitation and metabolite profiling. Li et al.122 described the use of a hybrid QTRAP MS/MS system for discovery PK assays plus metabolite profiling in the same analytical procedure. Because QTRAP MS/MS may be used as a triple quadrupole MS system, it can be used as part of a quantitative HPLC/MS/MS system. Because QTRAP MS/MS also has linear ion trap capabilities, it can be used for metabolite screening and characterization—essentially it combines the capabilities of a triple quadrupole mass spectrometer and a linear ion trap mass spectrometer. 

MS vendors continue to improve their triple quadrupole mass spectrometers. Typically, the latest models of these MS/MS systems are more sensitive than previous systems and scan faster than the... 

Yang, L. et al. 2001. Evaluation of a four-channel multiplexed electrospray triple quadrupole mass spectrometer for the simultaneous validation of LC/MS/MS methods in four different preclinical matrixes. Anal. Chem. 73 1740. 

A Waters Micromass triple quadrupole mass spectrometer was used with an electrospray ionization interface in positive ionization mode desolvation gas (400), cone gas (70), collision gas (2.74 x 10 3 mbar), capillary (3.0 kV), cone (14 (kV), source temperature (105°C), and desolvation temperature (300°C). The detection and quantitation of amlodipine and nimodipine were performed... 

Usually, concentration is measured as a pressure and may differ widely according to the type of mass spectrometer used. The triple quadrupole mass spectrometer may operate with pressures up to 1 x 10 1 Pa in the reaction region. At the other extreme, ion cyclotron resonance mass spectrometers operate poorly at pressures >1 X 10 4 Pa. A pressure of 1 x 10 4 Pa may be regarded as fairly high pressure for FT-ICR measurements. Converting the pressure into a more normal value of concentration means that reactions are carried out at concentrations < 10 9M (often several orders of magnitude < 10 0 M). 

Personnel Choosing an appropriate technique sometimes comes down to having the right person on your staff to perform the technique. If you, or no one in the lab, had had experience with the hydroxyl value titration, it might not have been an option in the Bulging Drum Problem. Certainly, if the operator of your triple quadrupole mass spectrometer is on vacation and there is no back-up operator, another method, or sending the samples to another lab, may be necessary. Should the method need to be transferred to another lab, does that lab have the requisite people for the job ... 

Detection modes of single and triple quadrupole mass spectrometers... 

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