Selected reaction monitoring

SIM MID Selected ion monitoring Multiple ion detection In practice used interchangeably the term SIM is recommended. 

HR-SIM High-resolution selected ion monitoring To avoid isobaric interferences 

SRM MRM Selected reaction monitoring Multiple reaction monitoring SIM in a tandem MS mode More than one reaction per cycle 

Every ionization method exhibits compound-dependent ionization efficiencies (Chap. 2.4). Whether a specific compound is rather preferred or suppressed relative to another greatly depends on the ionization process employed to deliver the ions to the mass analyzer. These circumstances require a careful calibration of the instrument s response versus the sample concentration for correct quantitation [6,7,50]. While relative signal intensities are perfect for qualitative analysis, i.e., for compound characterization, some means of measuring absolute intensities would be preferred in quantitation. Basic considerations on how to approach a quantitative analysis by mass spectrometry are given below [51-54]. Readers interested in a treatment of all aspects of quantitative analysis by mass spectrometry may refer to the highly recommended book by Boyd, Basic, and Bethem [50]. 

Instrument operation in SRM measurements is exactly identical to that used in the product-ion analysis (Section 4.2) except that instead of acquiring a full-scan spectrum, only the products selected are monitored. A triple-quadrupole instrument is ideally suited for SRM experiments, although magnetic-sector and Qrr instruments have also been used. 

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SRM. selected reaction monitoring SSMS. spark source mass spectrometry... 

The most common modes of operation for ms/ms systems include daughter scan, parent ion scan, neutral loss scan, and selected reaction monitoring. The mode chosen depends on the information required. Stmctural identification is generally obtained using daughter or parent ion scan. The mass analyzers commonly used in tandem systems include quadmpole, magnetic-sector, electric-sector, time-of-flight, and ion cyclotron resonance. Some instmments add a third analyzer such as the triple quadmpole ms (27). 

The MS-MS equivalent of this technique is known as selected-decomposition monitoring (SDM) or selected-reaction monitoring (SRM), in which the fragmentation of a selected precursor ion to a selected product ion is monitored. This is carried out by setting each of the stages of mass spectrometry to transmit a single ion, i.e. the precursor ion by MSi and the product ion by MS3 (see Figure 3.8 above). 

Table 5.2 Selected-reaction monitoring (SRM) transitions nsed for MS-MS detection of the pesticides studied in the systematic investigations on APCI-MS signal response dependence on eluent flow rate. Reprinted from J. Chro-matogr.. A, 937, Asperger, A., Efer, J., Koal, T. and Enge-wald, W., On the signal response of various pesticides in electrospray and atmospheric pressure chemical ionization depending on the flow rate of eluent applied in liquid chromatography-mass spectrometry , 65-72, Copyright (2001), with permission from Elsevier Science...

Figure 5.58 Reconstructed LC-MS-MS ion chromatograms for selected-reaction monitoring of methoxyfenozide using the m/z 367 to m/z 149 transition from the continual post-column infusion of a standard solution of analyte during the HPLC analysis of a...

Figure 5.66 Molecular structures of Idoxifene and its deutrated internal standard ds-Idoxifene. Reprinted from J. Chromatogr., B, 757, Comparison between liqnid chromatography-time-of-flightmass spectrometry and selected-reaction monitoring liqnid chromatography-mass spectrometry for qnantitative determination of Idoxifene in hnman plasma , Zhang, H. and Henion, I., 151-159, Copyright (2001), with permission from Elsevier Science.

Figure 5.69 Calibration curves obtained from (a) LC-ToF-MS and (b) LC-MS-MS using selected-reaction monitoring for Idoxifene in human plasma, fortified from 5 to 2000 ngml for LC-ToF-MS and 0.5 to 1000 ngml for LC-MS-MS with a triple quadrupole is the correlation coefficient, a measure of the quality of calibration (see...

Selected-reaction monitoring (See Selected-decomposition monitoring)... 

Tian, Q. et al., Screening for anthocyanins using high-performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry with precursor-ion analysis, product-ion analysis, common-neutral-loss analysis, and selected reaction monitoring, J. Chromatogr. A, 1091, 72, 2005. 

Figure 1 Selected reaction monitoring of the two primary chlormequat ions using MS/MS...

The instrument scan mode called selected reaction monitoring (SRM) is generally used for quantitative applications. SRM is similar to selected ion monitoring (SIM) in single quadrupole MS. The difference is that a product ion from the decomposition reaction in the collision cell is measured instead of a single ion formed in the... 

Plant material is homogenized in acetone followed by addition of water. The filtered extract is diluted with acetone-water (2 1 v/v) and filtered through a syringe filter. The sample extract is diluted 1 1 with a deuterated azinphos-methyl internal standard and analyzed using LC/MS/MS in the positive-ion selected reaction monitoring (-I-SRM) mode. 

Water samples, received from the respective groundwater trials, are analyzed by direct aqueous injection (DAI) by LC/ESI-MS/MS. A 1-mL volume of the water is pipetted into a 1.8-mL autosampler vial. The internal standard solution is added (200 qL) and mixed. The vials are capped and analyzed by LC/ESI-MS/MS using the selected reaction monitoring (SRM) mode. 

SIM, selected ion monitoring SRM, selected reaction monitoring MRM, multiple reaction monitoring. 

The software tools accompanying the QTRAP MS/MS allow set-up of multiple selected reaction monitoring (SRM) transitions for all likely metabolites after the major product ion transitions for the dosed compound are known. Because QTRAP MS/MS can monitor up to 100 SRM transitions during a single assay, the SRM transitions required for quantitation of the dosed compound and internal standard are obtained along with the possible metabolite transitions. During sample analysis, when a possible metabolite transition exceeds a preset threshold value, the QTRAP MS/MS performs an enhanced product ion (EPI) scan. When the assay is complete, the EPI scans can be used to determine whether the hits are metabolites, and if they are metabolites, what part of the molecule has changed. Thus, one analytical run provides both quantitative and metabolite information. 

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