Mass analyzers scan rate

System Analyzer type Ionization Electron energy Ion source Acquisition Mass range Scan rate Resolution... 

MS Method System Analyzer type Ionization Ion source Acquisition Mass range Scan rate Temperature Mode SIM mode Thermo Scientific ITQ 900 Ion trap MS with external ionization El, 70 eV 200 °C SIM miz 76,78 0.5 s/scan... 

Fig. 11.16. Representation of three tandem mass spectrometry (MS/MS) scan modes illustrated for a triple quadrupole instrument configuration. The top panel shows the attributes of the popular and prevalent product ion CID experiment. The first mass filter is held at a constant m/z value transmitting only ions of a single mlz value into the collision region. Conversion of a portion of translational energy into internal energy in the collision event results in excitation of the mass-selected ions, followed by unimolecular dissociation. The spectrum of product ions is recorded by scanning the second mass filter (commonly referred to as Q3 ). The center panel illustrates the precursor ion CID experiment. Ions of all mlz values are transmitted sequentially into the collision region as the first analyzer (Ql) is scanned. Only dissociation processes that generate product ions of a specific mlz ratio are transmitted by Q3 to the detector. The lower panel shows the constant neutral loss CID experiment. Both mass analyzers are scanned simultaneously, at the same rate, and at a constant mlz offset. The mlz offset is selected on the basis of known neutral elimination products (e.g., H20, NH3, CH3COOH, etc.) that may be particularly diagnostic of one or more compound classes that may be present in a sample mixture. The utility of the two compound class-specific scans (precursor ion and neutral loss) is illustrated in Fig. 11.17.

Finally, one concept that must be included in assessing quantitation by HRMS is the effective scan rate of the system. Quadrupole and time of flight mass analyzer are capable of rapid scan rates for SRM-type quantitation, with individual dwell times (quad) or scans (TOF) at 10-50 milliseconds possible. This permits acquisition of numerous data points across a chromatographic peak, which is critical for accurate and precise quantitation. Mass resolution is unaffected by changes in dwell time/scan... 

If both mass analyzers are scanned at the same rate with a... 

After optimization of the method, the following analytical conditions were used silica capillary with stationary phase HP-5MS (30 m x 0.25 mm internal diameter, 0.25 pm film thickness) column gradient temperature started at 80 °C and increased at a rate of 10 °C/min to 280 °C injection temperature was fixed at 250 °C and helium was used as a carrier gas with constant flow rate of 1 mL/min. A mass spectrometry detector with single quadrupole was used as analyzer, operated at 150 °C with an acquisition scan rate of 50-800/n/z. 

In terms of mass spectrometry instrumentation, the currently available instruments such as time-of-flight (TOF) analyzers and hybrid quadrupole-TOF analyzers are able to acquire complete mass spectra at rates compatible with fast CE separations. As CE or ultrafast chromatography replaces conventional, slow HPEC applications, TOF-based mass spectrometers will be needed to replace the less efficient scanning types of instruments such as quadrupoles and ion traps for most high-throughput applications. FTICR mass spectrometry remains unsurpassed in terms of resolution and mass accuracy for both MS and MS-MS applications. However, the throughput of FTICR mass spectrometric... 

Although 3D traps have been extensively used, during the early to mid-2000s, for structural elucidation of metabolites, overall a slower scan rate compared to TOF mass analyzers, in combination with limited ion capacity and trapping efficiency are the limitations associated with the QITs for becoming the mass analyzer of choice for quantitative/qualitative bioanalysis. Most importantly, 3D traps can only simulate SRM by acquiring full-scan MS data, true SRM scan modes can only be... 

Co., Palo Alto, CA.) One rL of each extract was injected (splitless mode 30 s valve delay 200 0 injector temperature) into a capillary column (DB-wax or DB-Sms. 60 m length x 0.25 mm i.d. x 0.25 pm film thickness (d,) J W Scientific, Poison, CA). Helium was u.scd as carrier gas at a constant How rate of 0.96 mI7min. Oven temperature was programmed from 40 C to 200 0 at a rate of 3 Omin with initial and final hold times of 5 and 60 min, re.speclively. MSD conditions were as follows capillary direct interface temperature, 280 C ionization energy, 70 eV mass range, 33-350 a.in.u. BM voltage, 1956 (Atune + 200V) scan rate, 2.2 scans/s. Bach SDB or DE extract was analyzed in duplicate. 

Orbitrap-based mass spectrometers (Hu et al., 2005 Scigelova and Makarov 2009) have seen rapid uptake into metabolite identification laboratories, mainly in the hybrid iontrap—Orbitrap configuration discussed below. The Orbitrap mass analyzer provides a resolution of up to 100,000 FWHM at m/z 200 at a 1 Hz acquisition rate. Mass accuracy is <2 ppm with internal calibration and is <5 ppm with external cabbration. It is stable over extended periods (days) when using external cabbration. The mass accuracy is also very good for low abundance ions and is reproducible from scan to scan. Dynamic range is >4,000 within a spectrum and acquisition rates of 10 Hz are possible at reduced resolution. 

With a few exceptions, most of the detectors used in GC were invented specifically for this technique. The major exceptions are the thermal conductivity detector (TCD, or katharometer) that was preexisting as a gas analyzer when GC began, and the mass spectrometer (or mass selective detector, MSD) that was adapted to accept the large volumes and the fast scan rates needed for GC peaks. Most recently, other spectroscopic techniques like IR and atomic plasma emission have been coupled to the effluent from gas chromatographs, serving as GC detectors. 

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