Tandem mass spectrometry calibration

Residues of isoxaflutole, RPA 202248 and RPA 203328 are extracted from surface water or groundwater on to an RP-102 resin solid-phase extraction (SPE) cartridge, then eluted with an acetonitrile-methanol solvent mixture. Residues are determined by liquid chromatography/tandem mass spectrometry (LC/MS/MS) on a Cg column. Quantitation of results is based on a comparison of the ratio of analyte response to isotopically labeled internal standard response versus analyte response to internal standard response for calibration standards. 

SEC-ESI-FTMS combines the size separation based technique of SEC with one of the most powerful mass spectrometric techniques of FTMS offering high mass accuracy (ppm), ultrahigh resolving power (>10(i) 6) and the capability to perform tandem mass spectrometry. The technique enables generation of oligomer elution profiles, which can be used for accurate calibration of standard SEC data. Coupling of SEC to ESI-MS is further described in ref. [710],... 

As analytical and bioanalytical methods must be validated before using them for routine sample analysis and after changing method parameters (see Chapter 8), instruments such as liquid chromatography coupled with mass spectrometry (LC-MS) or tandem mass spectrometry (LC-MS/MS), which are utilized to perform the analysis, should be calibrated and qualified. In addition, an instrument s performance should be tested for suitability prior to use on practically a day-to-day basis. 

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. 

Zrostlikova J, Hajslova J, Poustka J, Begany P (2002) Alternative calibration approaches to compensate the effect of co-extracted matrix components in liquid chromatography-electrospray ionization tandem mass spectrometry analysis of pesticide residues in plant materials. J Chromatogr A 973 13-26... 

Quantification of Hyperforin in Mice Brain by Liquid-Liquid Extraction and High-Performance Liquid Chromatography Electrospray Ionization Tandem Mass Spectrometry, Using External Calibration (No Internal Standard)... 

Phylloquinone, menaquinone, and menaphthone have been extracted from serum into supercritical CO2 and separated with SFC, with detection at 250 nm (127). Serum, supported on celite, was transferred to extraction cartridges and extracted with supercritical CO2 at 45°C prior to the analysis of benzodiazepines, anabolic agents, and nonsteroidal anti-inflammatory drugs by HPLC (128). Phenobarbital, butalbital, pentobarbital, and thiopental have been extracted from human serum prior to liquid chromatography-negative-ion electrospray tandem mass spectrometry analysis (129). The sample was extracted with supercritical CO2 at 40°C and 507 bar with static extraction for 5 min followed by dynamic extraction for 30 min. Calibrations graphs were linear for 1-60 pg/mL of each barbiturate and the detection limits were 23, 25, 50, and 225 ng/mL of thiopental, pentobarbital, butalbital, and phenobarbital, respectively. In the determination of the cited analytes in serum spiked at the 10- and 50-pg/mL levels, the recoveries were 94.2-106.9% and the RSDs were 1.14-5.18% (three replicates). 

An example of the application of the wide isolation window in tandem mass spectrometry is the detection and quantitative imaging of cocaine in postmortem human brain tissue (Reich et al., 2008 Reich et al., 2010). In this instance, it was determined necessary to develop an MS wide isolation window method because of interfering background ions. Cocaine detected in brain tissue was confirmed by matching six MS product ions with those from a cocaine standard. For the quantitation of cocaine analyzed from the tissue, the trideuterated ( Hs) internal standard was spiked beneath the tissue at known concentrations before matrix application to develop a calibration curve. The MS wide isolation method was then employed for the analysis of cocaine and cocaine-fi 3. Cocaine was analyzed successfully and quantified using this approach. 

In this section the mass analyzers that are important in current practice of trace level quantitation are described in some detail. Before starting the descriptions of specific analyzers, a topic of general applicability (calibration of the m z axis) is discussed. In addition, it should be mentioned here that an extremely important component of any mass spectrometer is the vacuum system this is discussed separately (Section 6.6). Another topic that is important for tandem mass spectrometry is that of colli-sional activation of ions, and discussion is also deferred till later (Section 6.5). 

Various mass spectrometers such as a single quadrupole, triple quadrupole, and quadrupole ITMSs are used for the detection of explosives. However, the ITMS has several advantages for homeland security applications. For example, the quadrupole ion trap has high sensitivity with a full scan mode and has tandem mass spectrometry (MS/MS) capabilities. Furthermore, the quadrupole ion trap is robust, and complicated calibrations are not necessary with this instrument format. 

Reference values for the acylcarnitines are derived from >500 patients, mostly pediatric (0.2-16 yrs), evaluated for metabolic disorders in the author s laboratory but with no manifest biochemical evidence of disease. Individuals with any markedly abnormal values were discounted. The analytical method used was tandem mass spectrometry with electrospray ionization. Internal standards used were stable isotope-labeled analogs of acetyl, propionyl, butyryl, octanoyl and palmitoyl carnitine. The values for straight-chain C2, C3, C4, C5, C6, C8, CIO, C14, C16 and Cl8 1 species are in pmol/1 and are derived from calibration curves using analytical standards all other values are ratios of the signal for the compound to an appropriate internal standard. All values are mean + 2 std. dev. except where a range is given... 

Gerssen A, van Olst EH, Mulder PP, de Boer J. In-house validation of a liquid chromatography tandem mass spectrometry method for the analysis of lipophilic marine toxins in shellfish using matrix-matched calibration. Anal Bioanal Chem 2010 397 3079-88. 

Buko, A. M., L. R. Phillips, and B. A. Fraser Peptide Studies Using a Fast Atom Bombardment High Field Mass Spectrometer and Data System 1-Sample Introduction, Data Acquisition and Mass Calibration. Biomed. Mass Spectrom. 10, 324 (1983). McLafferty, F. W., ed. Tandem Mass Spectrometry. New York Wiley. 1983. Cheng, M. T, M. P. Barbalas, R. F. Pegues, and F. W. McLafferty Tandem Mass Spectrometry Structural and Stereochemical Information from Steroids. J. Amer. Chem. Soc. 105, 1510 (1983). 

Arroyo D, Ortiz MC, Sarabia LA, Palacios F. Advantages of PARAFAC calibration in the determination of malachite green and its metabolite in fish by liquid chromatography-tandem mass spectrometry. J Chromatogr A 2008 1187 1-10. 

The resulting microdialysate samples were mixed (9 1) with acetyl-(3-methylcholine (internal standard, lng/pL), and a 950 pL portion was analyzed on a Discovery Cig column (50 cm x 2.1 mm i.d.). The method used 20 mM ammonium acetate/20mM heptafluorobutyric acid in methanol/water (1 9, pH 3.2) as the mobile phase at 0.4mL/min, and the analyte and internal standard were detected by tandem ion-trap mass spectrometry. The calibration graph was linear up to 500fg/pL of acetylcholine, and the on-column detection limit was 200 fg acetylcholine. 

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