Selected reaction monitoring quantification

The standard addition procedure is another method for recognising and overcoming potential matrix effects in quantification. Both alternatives, FIA—MS or FIA—MS—MS, can be performed using this procedure. Despite the increased expenditure because of a multiplication in analyses, the FIA approach combined with standard addition remains the faster technique even with the application of specific analytical MS—MS techniques such as product-, parent- or neutral loss scans applying selected reaction monitoring (SRM). The greatest drawback of this technique is that the compounds to be quantified must... 

A selective, sensitive, and rapid hydrophilic interaction liquid chromatography with electrospray ionization tandem mass spectrometry was developed for the determination of donepezil in human plasma [32], Donepezil was twice extracted from human plasma using methyl-ferf-butyl ether at basic pH. The analytes were separated on an Atlantis HILIC Silica column with the mobile phase of acetonitrile ammonium formate (50 mM, pH 4.0) (85 15, v/v) and detected by tandem mass spectrometry in the selective reaction monitoring mode. The calibration curve was linear (r = 0.9994) over the concentration range of 0.10-50.0 ng/ ml and the lower limit of quantification was 0.1 ng/ml using 200 /d plasma sample. The CV and relative error for intra- and inter-assay at four quality control levels were 2.7% to 10.5% and —10.0% to 0.0%, respectively. There was no matrix effect for donepezil and cisapride. The present method was successfully applied to the pharmacokinetic study of donepezil after oral dose of donepezil hydrochloride (10 mg tablet) to male healthy volunteers. 

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... 

Macek et al. [120] developed a method to quantitate omeprazole in human plasma using liquid chromatography-tandem mass spectrometry. The method is based on the protein precipitation with acetonitrile and a reversed-phase liquid chromatography performed on an octadecylsilica column (55 x 2 mm, 3 /im). The mobile phase consisted of methanol-10 mM ammonium acetate (60 40). Omeprazole and the internal standard, flunitra-zepam, elute at 0.80 0.1 min with a total rim time 1.35 min. Quantification was through positive-ion made and selected reaction monitoring mode at m/z 346.1 —> 197.9 for omeprazole and m/z 314 —> 268 for flunitrazepam, respectively. The lower limit of quantification was 1.2 ng/ml using 0.25 ml of plasma and linearity was observed from 1.2 to 1200 ng/ml. The method was applied to the analysis of samples from a pharmacokinetic study. 

As stated further above, under all circumstances trueness, accuracy and sensitivity of the assay should be demonstrated on a sufficient number of patient samples. In our view, however, the use of an additional, also easily realizable chromatographic dimension (online-SPE-LC-MS/MS) [67, 68] without a doubt represents the analytical state of the art in immunosuppressant TDM. Nowadays tandem MS instruments are used almost exclusively for the detection and quantification of analytes. The detection of analytes is generally performed in the selected reaction monitoring (SRM, synonym MRM) mode. Depending on which instrumentation is used, an analysis can be completed within two to four minutes. 

At about the same time, our laboratory has reported the development and validation of an LC tandem MS assay for as much as six TKIs simultaneously. The proposed LC-MS/MS method allows the simultaneous determination of clinically relevant ranges of concentrations for the six major TKIs currently in use imatinib, dasatinib, nilotinib, sunitinib, sorafenib, and lapatinib [122], Plasma is purified by acetonitrile protein precipitation followed by reversed-phase chromatographic separation. Analyte quantification is performed by electrospray ionization-triple quadrupole mass spectrometry by selected reaction monitoring (SRM) detection using the positive mode. This was the first broad-range LC-MS/MS assay covering the major currently in-use TKIs. 

Kim et al. [55] developed an LC-MS-MS method, based on positive-ion APCI mode and selected-reaction monitoring (SRM), for the doping analysis of 19-nortestosterone and three of its esters in plasma of race horses. The limits of quantification are 0.16, 0.1, 2.0, and 5.0 ng/ml for 19-nortestosterone, and its phenylpropionate, decanoate, and cyclopentanepropionate ester, respectively, using 2 ml of plasma. The method enabled detection of 19-nortestosterone np to 23 days... 

The quantification of the metabolites of CYPs 2D6, 3A4, and 2C19 reactions is carried out using a SCIEX API 3000 mass spectrometer, running in the positive ion, selected reaction monitoring (SRM) mode. The HPLC gradient system used consists of two solvent mixtures. Solvent mixture A (SMA) consists of 94.9% H20, 5% MeOH, and 0.1% formic acid and solvent mixture B consists of 94.9% MeOH, 5% H20, and 0.1% formic acid. The analytical column used is a Develosil Combi-RP5, 5 pm, 3.5x20mm (Phenomenex, Inc., Torrance, CA), with a mobile phase flow rate of 1.1 mL/min. A short run time (1 min) HPLC method is used because of the specificity of the mass spectrometer and the lack of matrix effects (this was thoroughly... 

In both tandem-in-space and tandem-in-time instruments, the most common experiment is for the first analyzer to select specific ions from the total ion beam arriving from the ion source. Next, the selected ions undergo collision-induced dissociation (CID) in a pressurized cell followed by the analysis of the product ions in the second analyzer. In tandem-in-time the same analyzer is used for both scans, but at different times. The resulting product ion spectra (or precursor and neutral loss spectra in other forms of MS/MS analysis) provide vital structural information for the identification of small molecules (such as drug metabolites) as well as complex biomolecules. Selected reaction monitoring (SRM), another mode of MS/MS operation, provides highly specific and sensitive quantification of target analytes. 

The intensity of the current produced by analyte ions is relevant in quantification. Limits of detection are improved when fragmentation is reduced or eliminated and the ion current, attributable to the analyte, is present as a single species. For instance, using Cl often improves both detection and quantification limits when compared to El, although the controlled fragmentation used in selected reaction monitoring can also improve detection limits. Fragmentation as it applies to specific quantification techniques for small molecules is discussed in connection with the quadrupole family of instruments (Sections 3.3.3.1 and 3.3.5). Quantification for biopolymers, particularly proteins, is presented in Section 3.5.1.9. 

Most important use of CID is in selected reaction monitoring (SRM) for quantification... 

Simultaneous quantification of 11 compounds found in ayahuasca (A popular Amazonian botanical medicine and religious sacrament) has been achieved using direct injection/Uquid chromatography- electrospray ionization (ESI)-selected reaction monitoring (SRM) - tandem mass spectrometry procedure [45, 46]. 

A mass spectrometric mode called selected reaction monitoring (SRM) is very useful for low level quantification of ergot alkaloids [28, 29]. In this approach, the... 

Fitzgerald RL, Griffin XL, Yun YM, Godfrey RA, West R, Pesce AJ, et al. Dilute and shoot analysis of drugs of abuse using selected reaction monitoring for quantification and full scan product ion spectra for identification. J Anal Toxicol 2012 36 106-11. 

A modern strategy for quantitative analysis without chromatography utilises the specificity of MS/ MS. Here, quantification is based on monitoring of the fragmentation of ions with a second analyser (selected reaction monitoring by MS/MS). Only few authors justify their use of MS/MS quantification by providing quantitative data. 

An LC-MS method to determine plasma levels of trimetazidine using an internal standard [l-(2,4,5-trimethoxybenzyl) piperazine]. Proteins are precipitated with trifluoroacetic acid the neutralized supernatant is separated on a C(8) column with methanol aqueous 0.11% triethylamine adjusted to pH 3.3 with formic acid (1 4, v/v). Test time is 8 min. An ion trap analyzer with an AP-CI interface is used for detection, in the selected reaction-monitoring mode. Lowest quantification limit 1.5 ng/ml. Used in bioequivalence studies. 

Coran et al. (1998) developed two methods to simultaneously determine Ci2 i6 trimethylammonium using two techniques of ionization, continuous flow FAB (CF-FAB) and ion spray ionization (ISI). One of the methods was based on FIA-ISI to avoid previous separation and quantification was carried out in selected ion monitoring (SDVt) and selected reaction monitoring (SRM) mode. On comparing the two methods, FTA-ISI was more sensitive (detection limit of 10 pg/ziL) than CF-FAB. Two samples of hair conditioner were quantified using the proposed methods and only C16 trimethylammonium was found. 

Multiple reaction monitoring (MRM) and selected reaction monitoring (SRM) are two terms for the same operation. The general goal is to quantify analytes whereas the modes presented below are dedicated to structural analysis. They are not really adapted to quantification analysis because they generally supply limits of detection insufficiently low for trace analysis. We saw at the beginning of this chapter that a quadrupole supplies detection limits that are high when used in the full scan mode due to the principles of operation. 

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