Tandem mass spectrometry purpose

Multidimensional or hyphenated instmments employ two or more analytical instmmental techniques, either sequentially, or in parallel. Hence, one can have multidimensional separations, eg, hplc/gc, identifications, ms/ms, or separations/identifications, such as gc/ms (see CHROMATOGRAPHY Mass spectrometry). The purpose of interfacing two or more analytical instmments is to increase the analytical information while reducing data acquisition time. For example, in tandem-mass spectrometry (ms/ms) (17,18), the first mass spectrometer appHes soft ionization to separate the mixture of choice into molecular ions the second mass spectrometer obtains the mass spectmm of each ion. 

All previous discussion has focused on sample preparation, i.e., removal of the targeted analyte(s) from the sample matrix, isolation of the analyte(s) from other co-extracted, undesirable sample components, and transfer of the analytes into a solvent suitable for final analysis. Over the years, numerous types of analytical instruments have been employed for this final analysis step as noted in the preceding text and Tables 3 and 4. Overall, GC and LC are the most often used analytical techniques, and modern GC and LC instrumentation coupled with mass spectrometry (MS) and tandem mass spectrometry (MS/MS) detection systems are currently the analytical techniques of choice. Methods relying on spectrophotometric detection and thin-layer chromatography (TLC) are now rarely employed, except perhaps for qualitative purposes. 

The above-mentioned method is effective in identifying the molecules of detected ions. However, because PVDF film is not permeable to light, it is difficult to observe tissue sections. To resolve this problem, we developed a method to fix tissue sections on transparent film, and then performed MS on those sections.6 We used a conductive film because we expected the ionization efficiency would increase when the electric charge accumulation on the sample was reduced. The film used for this purpose was a polyethylene terephthalate (PET) film with a thickness of 75-125 pm, having a 5 15-nm-thick layer of evaporated oxidation indium tin (ITO) upon it (ITO film). This film is used in touch-panel displays because of its high transparency and superior conductivity. We used it to perform MS/MS for tissue sections and succeeded in identifying multiple proteins from mass spectra.6 Therefore, the further development of this method will enable the application of the mass-microscopic method to observe tissue by optical microscope and to perform tandem mass spectrometry (MSn) at the observation part, simultaneously, enabling the identification of molecules included the part. 

An ultrapure polymer is made of chains of the type G1-AAAAAAA-G2, where A is the repeat unit and G1 and G2 are end-groups. One considers the mass number of one of the MS peaks, subtracts the mass of the cation (e.g., H, Li, Na, Ag), and then repeatedly subtracts the mass of the repeat unit, until one obtains the sum of the masses of G1 + G2. For this purpose, a linear best fit can also be used. Tandem mass spectrometry is particularly useful since, from the analysis of ion fragmentation patterns, one can deduce the mass of G1 and, separately, the mass of G2. 

Atmospheric Pressure Chemical Ionization (APCI) is coupled to Tandem Mass Spectrometry (MS/MS) for the purpose of analyzing vapor phase perfume mixtures. Air-borne fragrances are analyzed directly by APCI/ MS/MS without the need for time consuming and potentially adulterating trapping and chromatography steps. Volatile fragrance chemicals have been rapidly identified by this novel technique as they emanate from vials or directly from skin. 

Traditional analytical approaches such as GC-MS, HPLC fluorescence, and conventional LC-MS, are not sufficiently sensitive to quantify the low-pg/mL levels of corticosteroids in bodily fluids [4], The purpose of this work was to develop an ultrasensitive and selective approach to quantify corticosteroids present at extremely low, but biologically meaningful concentration in body fluids. A selective solid-phase extraction (SPE) and reversed-phase capillary LC coupled to tandem mass spectrometry (uLC-MS/MS) strategy was employed to achieve a high concentration sensitivity. 

In order to expand the CE potential for quantification, the selected ion monitoring (SIM) mode is to be preferred for its high selectivity and sensitivity. It can be noted that sensitivity improvement over UV-VIS spectrometry is closely related to the nature of the compound (molar absorptivity or protonation or deprotonation capacity) the awaited gain in sensitivity can diverge from about 10 to IO". Tandem mass spectrometry (MS ) appears to be relevantly advantageous for quantitative purposes [23, 37]. In fact, the selectivity issue is of crucial importance in chiral CE due to the complex composition ofthe BGE. 

In cases where the toxin is metabolized, excreted, or otherwise not available for immunological or chemical detection, it may be possible to verify an exposure to ricin or castor seeds for forensic purposes by detecting other unique components of the R. communis plant. PCR can detect residual castor seed DNA in most ricin preparations. Ricinine, an alkaloid (3-cyano-4-rnethoxy-A -rnethyl-2-pyridone) produced by castor seeds, has been proposed as a biomarker for ricin exposure the detection limit for ricinine by electrospray ionization tandem mass spectrometry is as low as 0.083 ng/mL in urine of exposed subjects (Johnson et al., 2005). 

As for gas chromatography coupling systems, tandem mass spectrometry is now the method of choice for identification and quantitation purposes of herbicides, with ion trap or triple-quadrupole based Although triple quadrupole MS/MS is more sensitive... 

Corn-based foods followed by fumonisin B2 (FB2).The problems and risks associated with fumonisin contamination have resulted in the development of precise, reliable and sensitive methods for its determination in corn and corn-based foods (Magan Olsen, 2004, as cited in Silva et al., 2009). Therefore, the quality parameters in the analysis of FBI and FB2 in corn-based products obtained with LC with fluorescence detector have been investigated (Silva et al, 2009). Furthermore, a comparison study between fluorescence detector (FD), mass spectrometry, and tandem mass spectrometry with a triple quadrupole (QqQ) analyzer using an electrospray ionization interface for the determination of fumonisin B1 and B2 in corn-based products has been performed. A comparative study of the three LC detectors, FD, single quadrupole, QqQ for the analysis of fumonisins in corn samples has been performed. The response achieved by the three detectors was sensitive enough to study the maximum contents established by the EU legislation. These LC detectors would be appropriate for quantification purposes but the acquisition of at least two transitions achieved with QqQ provided a univocal identification. 

In addition, a number of advanced analytical techniques, such as low temperature luminescence spectroscopy, tandem mass spectrometry (MS/MS), Fourier-Transform IR-spectroscopy and nuclear magnetic resonance spectrometry have been successfully applied to PAH analysis. For instance, low temperature luminescence spectrometry, sometimes in combination with laser excitation, was used for the analysis of PAH in various matrices without prior separation, which is attractive especially for screening or finger-printing purposes (10, 73). However, a wider application for routine analysis is at present inhibited by the limited availability of the required equipment. The same remark applies to tandem mass spectrometry, FT-IR spectroscopy and NMR. All three techniques, however, are increasingly used for the detection and identification of novel PAH species and derivatives and efforts are continuing towards coupling IR and NMR as detectors to GC and HPLC (74) respectively. 

Sometimes a test for more than one protein is needed and mass spectrometry is the method of choice for that purpose. A good example for this would be the use of tandem mass spectrometry to screen neonates for metabolic disorders such as amino acidemias (e.g., phenylketonuria—PKU), organic acidemias (e.g., propionic acidemia—PPA), and fatty acid oxidation disorders (e.g.. Medium-chain acyl-CoA Dehydrogenase deficiency—MCAD) [9]. Although the price of this capital equipment could be high, costs of using it as a sensor is quite low (usually < U.S. 50.00 to screen for more than 20 metabolic disorders), and many states in the United States provide the service to newborns during the first week of life. 

Once the identity of phosphopeptides in a digestion mixture is revealed, it is imperative to recognize which amino acid residue (Ser, Thr, or Tyr) is phospho-rylated. This task is accomplished by determining the amino acid sequence of peptide fragments in the protein digest after their fractionation into individual components by RP-HPLC, either off- or online with tandem mass spectrometry [34], The tandem MS methods described below have proved to be practical for this purpose. 

Triple quadrupole instruments (Section 6.4.3) have not previously been considered suitable for use with MALDl sources in view of their nature as scanning analyzers (serial recording of a mass spectrum resulting in very low duty cycle in full spectral acquisitions) with a limited miz range. However, for the present purpose of small molecule quantitation by MALDl, neither of these limitations applies. In particular, if the so-called multiple reaction monitoring (MRM) mode of tandem mass spectrometry is... 

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