The Use of Tandem Mass Spectrometry

This will be discussed in greater detail in Chapter 5, but at this point it is worthwhile to consider a brief example of the analytical capabilities of MS-MS. 

A reported method for the screening for transformation products of a number of pesticides [16] provides an elegant example of the complementary nature of the product-ion, precursor-ion and constant-neutral-loss scans (see Section 3.4.2 above). 

Were these to be true unknowns, then product-ion scans could be carried out on these molecular species in an attempt to obtain further structural information. 

In this chapter, the main aspects of mass spectrometry that are necessary for the application of LC-MS have been described. In particular, the use of selected-ion monitoring (SIM) for the development of sensitive and specific assays, and the use of MS-MS for generating structural information from species generated by soft ionization techniques, have been highlighted. Some important aspects of both qualitative and quantitative data analysis have been described and the power of using mass profiles to enhance selectivity and sensitivity has been demonstrated. 

Chapman, J. R., Practical Organic Mass Spectrometry, 2nd Edn, Wiley, Chichester, UK, 1993. 

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The differentiation of diastereomeric Ni11 iV-glycoside complexes is possible with the use of tandem mass spectrometry. 

As illustrated below, the mass spectra of particles in ambient air can be (not surprisingly) quite complex. The use of tandem mass spectrometry would therefore be quite valuable, and indeed, such an instrument has... 

Another advantage of the use of tandem mass spectrometry is the ability to isolate a particular ion such as the molecular ion of the... 

The use of tandem mass spectrometry <88MI 711-08) to study the collision-induced dissociation of protonated heterocycles has invited further attention in the 1990s. Thus following collisional acti-... 

Both ESI and APCI generate molecular ions from polar and labile biomaterials with remarkable ease and efficiency. But the amount of structural information that can be deduced from ESI spectra, in particular, is rather limited. Thus, only the use of tandem mass spectrometry (MS/MS) together with liquid chromatography opens further dimensions in the field of bio-organic analysis (Fig. 1). Beside retention data and UV spectra one can obtain both molecular mass and substructure specific information of any analyte out of a complex matrix. 

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. 

Another ambient method, called AP-DIOS-MS, was also used for the identification of amphetamines and fentanyls in forensic samples. The principle is similar to that of DIOS, but occurs at atmospheric pressure. The use of tandem mass spectrometry (MS/MS) allowed unambiguous identification of the amphetamines and fentanyls (Pihlainen et al. 2005). AP-DIOS-MS/MS was also successfully applied to the identification of authentic compounds from drug seizures. Common diluents and tablet materials did not disturb the analysis and compounds were unequivocally identified. The limits of detection (LODs) for amphetamines and fentanyls with AP-DIOS-MS/ MS were 1-3 pmol, indicating excellent sensitivity of the method (Pihlainen et al. 2005). Protein digest analysis (250 finol of bovine serum albumin) by AP-DIOS-MS was also performed... 

Although GC is the ideal technique for volatile substances such as PASs, the presence of chromophore groups in moss constituents led Schulz and Albroscheit (1989) to analyse them by liquid chromatography (LC) with ultraviolet detection. Then Hiserodt et al. (2000) proposed the use of tandem mass spectrometry (LC-MS/MS) to identify atranorin... 

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