Tandem chemical laser technique

As for sample preparation, SPE-GC has become more popular than NPLC-GC. Aqueous samples are not compatible with NPLC-GC, while RPLC-GC has never become a success. SPE-GC-(tandem)MS and SPE-GC-AED systems have demonstrated excellent performance. SPME is an equilibrium technique while SPE affords exhaustive extraction of the analytes. Laser desorption injection in LD-GC-MS can uniquely provide an additional dimension of spatial information for 2D surface chemical mapping [221]. 

A different strategy has been applied in our work, that emphasizes the importance of DNA stability on hole transfer within double-stranded DNA. This work is based on determination of the overall yield of oxidized nucleosides that arise from the conversion of initially generated purine and pyrimidine radical cations within DNA exposed to two-photon UVC laser pulses. On the one hand, this work benefits from the excellent current knowledge of chemical reactions involving the radical cations of DNA bases, and on the other hand, from major analytical improvements that include recent availability of the powerful technique of high performance liquid chromatography-electrospray ionization-tandem mass spectrometry (CLHP-ESI-MS/MS) [16-18]. 

Law KP (2010) Laser desorption/ionization mass spectrometry on nanostructured semiconductor substrates DIOS (TM) and QuickMass (TM). Int J Mass Spectrom 290 72-84 Law KP, Larkin JR (2011) Recent advances in SALDI-MS techniques and their chemical and bioanalytical applications. Anal Bioanal Chem 399 2597-2622 Lewis WG, Shen Z, Finn MG, Siuzdak G (2003) Desorption/ionization on silicon (DIOS) mass spectrometry background and applications. Int J Mass Spectrom 226 107-116 Li Q, Alonso R, Renner SA, Winefordner JD, Powell DH (2005) Desorption/ionization on porous silicon mass spectrometry studies on pentose-borate complexes. Anal Chem 77 4503-4508 Lin Z, Zhang S, Zhao M, Yang C, Chen D, Zhang X (2008) Rapid screening of clenbuterol in urine samples by desorption electrospray ionization tandem mass spectrometry. Rapid Commun Mass Spectrom 22 1882-1888... 

After separation, the compounds are ionized prior to mass analysis. The most common techniques for ionization include chemical ionization (Cl), electron impact (El), electron spray ionization (ESI), and matrix-assisted laser desorption ionization (MALDI). Charged compounds are shutded into the mass analyzer which, depending upon the method, selects ions based on predetermined mass-to-charge ratio m/z) criteria, or scans within defined m/z ranges. If tandem mass spectrometry (MS/MS) is... 

It was not possible to use MS for the characterization and identification of chlorophylls and its derivatives until the development of desorption methods (desorption ionization) appropriate for nonvolatile and thermolabile compounds. The mass spectmm of chlorophylls has been obtained using laser desorption [92-94], field desorption [95], plasma desorption [96,97], fast atom bombardment (FAB) [28, 98-101], in-beam electron ionization [102], and electrospray ionization (ESI) [103]. A combination of the techniques of desorption and tandem mass spectroscopy (MS/MS) has also been used for the charactmzation of chlorophylls and derivatives [ 104—107]. The latest research in this field coupled HPLC with MS, using as ionization source FAB [108-110] or atmosphoic pressure chemical ionization (APCI) [111-115]. 

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