Selected reaction monitoring transition

Goto T, Ito Y, Yamada S, Matsumoto H, Oka H, High-throughput analysis of tetracycline and penicillin antibiotics in animal tissues using electrospray tandem mass spectrometry with selected reaction monitoring transition, J. Chromatogr A 2005 1100 193-199. 

Whereas most multiresidue methods employ SPE for sample enrichment, Grulick and Alder [80] utilized direct sample injection for the determination of 300 pesticides in water samples. A conventional reversed-phase LC separation was developed with gradient elution using a Cl 8 column with a run time of approximately 23 min. The LC was coupled to a triple quadrupole mass spectrometer with electrospray ionization in the positive ion mode. Two selected reaction monitoring transitions were collected for each analyte by means of repeated analyses (i.e., two sample injections). Because interfering signals were noted for many of these transitions, both the LC separation and confirmatory transitions were essential for correct analyte identification. 

Confirmatory methods are also required to demonstrate the selectivity of the method. This is favoring the use of MS techniques in combination with the equipments of chromatography (GC and EC), because they allow the confirmation simultaneous to primary detection (by monitoring several selected reaction monitoring transitions) without the need to use an independent analytic technique, saving time and effort. 

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...

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. 

Fig. 2.2.9 High-performance liquid chromatography-tandem mass spectrometric analysis of AdoMet and AdoHcy. The analytes were evaluated by multiple reaction monitoring with the following transitions m/z 399 -> 250 for AdoMet m/z 402 -> 250 for the internal standard, tridenterated AdoMet (AdoMet +3) m/z 385 -> 135 for AdoHcy m/z 390 ->- 135 for the internal standard, pentadenterated AdoHcy (AdoHcy+5). Mass spectrometric conditions are described in the text. TIC total ion current, SRM selected reaction monitoring (Figure courtesy of Dr. Ries Duran, Amsterdam)...

A liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was developed [33] and validated for the determination of donepezil in human plasma samples. Diphenhydramine was used as the IS. The collision-induced transition m/z 380 > 91 was used to analyze donepezil in selected reaction monitoring mode. The signal intensity of the m/z 380 —> 91 transition was found to relate linearly with donepezil concentrations in plasma from 0.1 to 20.0 ng/ml. The lower limit of quantification of the LC/MS/MS method was 0.1 ng/ml. The intra- and inter-day precisions were below 10.2% and the accuracy was between 2.3% and +2.8%. The validated LC/MS/MS method was applied to a pharmacokinetic study in which healthy Chinese volunteers each received a single oral dose of 5 mg donepezil hydrochloride. The non-compartmental pharmacokinetic model was used to fit the donepezil plasma concentration-time curve. Maximum plasma concentration was... 

To ensure that appropriate resolution and lack of interference is obtained during method development, it is highly recommended actively monitoring PLs and aware of the retention/elution times and intensity of the PLs relative to the retention/elu-tion times for the analytes of the interest. Table 2 summarizes several representative Selective Reaction Monitoring (SRM) transitions for PLs monitoring purpose during method development. 

The desorption of explosives from the passes was achieved by short wave infrared radiation. The vapors produced were drawn into a triple quadrupole mass spectrometer (MS/MS) and were monitored in the selected reaction monitoring (SRM). Ionization is carried out by corona discharge, followed by APCI. Ions formed from most explosives are M, [M-H]-, and adduct ions. One of these ions is selected to pass into the collision cell, to react with molecules of nitrogen, as a result of which a series of product ions are formed. In the SRM mode, one precursor ion and one product ion are chosen for each compound. The first and third quadruples are adjusted in order to enable SRM transition between these two ions. 

FIGURE 12.14 Selected reaction monitoring reflects the intensity of the transitions m/z 256 to 139 and 262 to 139. Note that the peak profiles are free from interference, indicating the specificity and selectivity of the measurement. The internal standard signal is 153 times the intensity of hydroxybupropion. Data provided by R.L. Walsky and R.S. Obach, Pfizer, New York, NY. 

For application with triple-quadrapole and especially (J-LIT instruments, a selected-reaction monitoring (SRM) procedure was developed for the sensitive and selective detection of phosphopeptides in proteomes with known amino-acid sequences [26]. A list of SRM transitions of potential phosphopeptides is generated for all expected tryptic peptides in the mixtme with Ser, Thr, or Tyr and for double-and triple-charge ions in the mass range of m/z 400-1600. The number of transitions included is limited by the maximum cycle time of 10 s, which assures that peptides in a 30 s wide peak are at least analysed twice. The procedure was applied to the cell cycle regulatory protein Cyclin B from Schizosaccharomyces pombe. 

Figure 55-2 Multi-analyte approach to the prenatal diagnosis of methylmalonic acidemia (cb/C complementation group) by metabolite analysis in ceil-free supernatant of amniotic fluid collected at 16 weeks of gestational age. The symbol marks internal standards. A, Determination of total homocysteine by LC-MS/MS (selected reaction monitoring, SRM, transition m/z 136 to m/z 90 and m/z 140 to m/z 94 for the d -labeled internal standard). The concentration of total homocysteine was l5.7pmol/L (0.7 to 2.0pmol/L). B, Determination of methylmalonic acid by LC-MS/MS (SRM, transition m/z 231 to m/z 119 and m/z 234 to m/z 122 for the d3-labeled internal standard). The concentration of methylmalonic acid was 8.7pmol/L, the reference interval for 16 to 19 weeks of gestational age is 0.2 to 0.7)j,mol/L. C, Determination of propionylcarnitine by LC-MS/MS (parent of m/z 85 scan, the [M+H] ion of C3 is m/z 274, m/z 277 for the interna standard). The concentration was 5.6pmol/L (i.5 to l.8pmoi/L),the C3/C4 ratio was 6.9 (0.9 to 2.6).

Figure 17 Quantifying salicylic acid in tomato. Selected reaction monitoring of the transition from m/z 267 to m/z 209 and from m/z 267 to m/z 223 from a tomato extract. Salicylic acid (Rt 6.45 min) (a) and 3-hydroxybenzoic acid (Rt 6.66 min) (b) can be observed at an S/N of 222 and 95, respectively.

Therefore, to determine if oxidized lipids were formed by enzymic processes or by free radical autoxidation, a first step is to visualize the distribution of products. This step requires previous knowledge of the maximum number of oxidized products, their chromatographic behavior and ions associated with mass spectrometric detection of each product. Quantitative analyses almost always require the use of appropriate, pure standards. For samples from more complex sources where the lipids of interest are present at low concentration there may be many interfering ions. In these instances, tandem mass spectrometry can be used to select pairs of precursor ions and product ions formed by collision-induced dissociation in a procedure called selected reaction monitoring (SRM). This type of analysis usually provides a significant improvement in signal to noise so that the product can be accurately quantified. With modem instruments many, up to hundreds, of these transitions can be measured in a single analysis. In conjunction with retention time... 

Figure 22-27 Chromatogram showing 20 ppb BPA leached into water from a polycarbonate hiking bottle. Reversed-phase chromatography on 150 x 3.9-mm column of 5-p.m RP18 with gradient elution over 15 min going from 40% to 100% solvent B. Solvent A = 0.1 wt% formic acid in HjO. Solvent B = acetonitrile. Mass spectral detection of negative ions with electrospray ionization and selected reaction monitoring of m/z 227 - 133 transition. (From M. Swartz, LCGC, January 2010, p. 42.]...

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