Transition metal ions mass spectrometry

We have undertaken a series of experiments Involving thin film models of such powdered transition metal catalysts (13,14). In this paper we present a brief review of the results we have obtained to date Involving platinum and rhodium deposited on thin films of tltanla, the latter prepared by oxidation of a tltanliua single crystal. These systems are prepared and characterized under well-controlled conditions. We have used thermal desorption spectroscopy (TDS), Auger electron spectroscopy (AES) and static secondary Ion mass spectrometry (SSIMS). Our results Illustrate the power of SSIMS In understanding the processes that take place during thermal treatment of these thin films. Thermal desorption spectroscopy Is used to characterize the adsorption and desorption of small molecules, In particular, carbon monoxide. AES confirms the SSIMS results and was used to verify the surface cleanliness of the films as they were prepared. 

The combination of laser ionization and Fourier transform mass spectrometry (FTMS) has proved to be ideally suited for the study of gas-phase ion-molecule reactions involving metal ions (1-7). The laser source permits the generation of virtually any metal ion in the periodic table from a suitable metal target (8). The FTMS (9-14) stores these ions in an "electro-magnetic bottle" for times t)rpically on the order of msec to sec (hours are possible) permitting the study of their chemistry and photochemistry. These studies are further facilitated by the unusual ion and neutral manipulation capabilities of the FTMS which permit complex multistep processes to be monitored in an MS fashion (1-4). These capabilities have made laser ionization-FTMS a prominent method in what has been a rapidly growing arsenal of techniques for studying gas-phase transition-metal ion species. 

Chen, R. and Li, L. (2001) Lithium and transition metal ions enable low energy collision-induced dissociation of polyglycols in electrospray ionization mass spectrometry. /. Am. Soc. Mass Spectrom., 12, 832-839. 

Aubriet and coworkers [30] performed an extensive study of MaOb oxides of the first transition metal series (M = Sc, Y, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn) by LA-FT-ICR-MS and secondary ion mass spectrometry (SIMS) (static SIMS). In addition to comparing the two mass spectrometric techniques, these researchers detected... 

Aubriet, F, Poleunis, C., Muller, J.F., Bertrand, R (2006) Laser ablation and secondary ion mass spectrometry of inorganic transition-metal compounds. Rart I comparison between static ToF-SIMS and LA-FTICRMS. Journal of Mass Spectrometry, 41, 527-542. 

In this paper, the photofragmentation of transition metal cluster complexes is discussed. The experimental information presented concerning the gas phase photodissociation of transition metal cluster complexes comes from laser photolysis followed by detection of fragments by ionization (5.). Ion counting techniques are used for detection because they are extremely sensitive and therefore suitable for the study of molecules with very low vapor pressures (6.26.27). In addition, ionization techniques allow the use of mass spectrometry for unambiguous identification of signal carriers. 

More recently, the catalytic activities of a large pool of transition-metal carbene complexes have been screened by means of ion-molecule reactions in tandem-MS experiments. [156-158] Different from the concepts and methods discussed so far, the latter experiments are not designed to study the fundamentals of mass spectrometry. Instead, sophisticated methods of modem mass spectrometry are now employed to reveal the secrets of other complex chemical systems. 

Advances in TIMS-techniques and the introduction of multiple collector-ICP-MS (MC-ICP-MS) techniques have enabled the research on natural variations of a wide range of transition and heavy metal systems for the first time, which so far could not have been measured with the necessary precision. The advent of MC-ICP-MS has improved the precision on isotope measurements to about 40 ppm on elements such as Zn, Cu, Fe, Cr, Mo, and Tl. The technique combines the strength of the ICP technique (high ionization efficiency for nearly all elements) with the high precision of thermal ion source mass spectrometry equipped with an array of Faraday collectors. The uptake of elements from solution and ionization in a plasma allows correction for instrument-dependent mass fractionations by addition of external spikes or the comparison of standards with samples under identical operating conditions. All MC-ICP-MS instruments need Ar as the plasma support gas, in a similar manner to that commonly used in conventional ICP-MS. Mass interferences are thus an inherent feature of this technique, which may be circumvented by using desolvating nebulisers. 

Applications of electrospray mass spectrometry (ESMS) to the study of reactions mediated by transition-metal complexes are reviewed. ESMS has become increasingly popular as an analytical tool in inorganic and organometallic chemistry, in particular with regard to the identification of short-lived intermediates of catalytic cycles. Going one step further, the coupling of electrospray ionization to ion-molecule techniques in the gas phase yields detailed information about single reaction steps of catalytic cycles. This method allows the study of transient intermediates that have previously not been within reach of condensed-phase techniques on both a qualitative and quantitative level. 

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