Field ionization and field desorption for collisional activation mass spectrometric determination of organic tin compounds

Abstract

Field ionization and field desorption spectra of a variety of organic tln compounds are reported. In contrast to the electron Impact spectra, In which only very low molecular Ion abundances are observed, the field ionization spectra are dominated by the molecular ion and show llttle If any fragmentatlon. The colllsional activation spectra of these fleld ionized molecules allow a rapid and unambiguous structure elucidatlon. Several examples are reported which demonstrate that the components of a mlxture of unknown composition can be ldentlfled unequivocally by using the comblnation of field ionization and collisional actlvatlon.Collisional activation (CA) spectra have been used extensively during the past 8 years in fundamental studies such as ion structure work ( I , 2). There is, however, a growing interest to explore the analytical potential of this method. Thus, it has been demonstrated that CA spectra of field ionized (3) or field desorbed (4-9) molecules give important structural information which is often not available from the field ionization (FI) and field desorption (FD) spectra alone. In addition we have demonstrated in 1974 that the CA technique can be used for a direct mixture analysis (3). For this purpose two-stage mass spectrometers such as double focusing instruments of reversed geometry (the magnetic sector precedes the electric sector) are of particular advantage. Here the ionized components of the mixture are mass selected and thus separated by the magnetic field before they undergo a highenergy collision with a neutral target gas. The resulting collision-induced fragments of each component are mass analyzed by using the electric sector. These collision-induced fragments reflect the structure of the unknown component of the mixture in much the same way as the electron impact spectrum of the pure sample does. A variety of applications of this technique using electron impact (EI) (10, 11), field ionization (3,12), or chemical ionization (CI) (13)(14)(15)(16)(17)(18)(19)(20) have been reported and reviewed (21,22).The most significant contributions to this field have been made by Cooks and co-workers (13-20) who used chemical ionization as primary ion source and were able to demonstrate that the analysis of unknown mixtures is possible with high sensitivity and little or no pretreatment of the sample.This and several subsequent papers will explore the analytical potential of a combination of field ionization or field desorption and collisional activation in more detail. Organic tin compounds have been chosen in this study as these compounds are produced industrially in large quantities, e.g., as fungicides, bactericides, and wood preservatives. As organic tin compounds are of medium toxicity, it is of interest to explore their ecological impact (23). Thus the availability of analytic techniques for their identification is of interest. EXPERIMENTAL SECTIONThe E1 spectra of the tin organic compounds were measured on a Varian MAT 44 S instrument (electron energy 70 eV, source temperature 250 "C). Th...

Tandem mass spectral studies of the fragmentation pathways of organotin compounds of general formula R3SnR?

“…Chambers et al 7 and Gielen and Jurkschat 11 reported the elimination of a hydrocarbon radical from the molecular ion to produce R 3 Sn ions of high abundance. In this work this elimination was observed for the Ph 3 SnR compounds whereas the alkyl analogues produced the RSn ion at 100% relative abundance (RA), closely followed by R 2 SnH , RR'SnH and RSnH 2 with RA values ranging from 100 to 47%. For the series of compounds RSnR' (R = butyl or pentyl) the nature of the dihydride is affected by R'.…”

“…[1][2][3][4][5] These studies show some common features, namely the absence of any significant molecular ion and the high stability of R 3 Sn (for R = Me, Et, n-Pr, Ph) and /or RSn (for R = n-Bu). Similar results were reported for a series of benzyltin derivatives, where the ease of cleavage of the Sn-R bond varies with the substituents, PhCH 2 = t-Bu b i-Pr b Et b Me.…”

“…The mass spectra from Bu 3 Sn R' (R' = allyl, vinyl, propyl, butyl) showed that the major fragmentation pattern processes occurred via formation of BuSn and BuSnH 2 in Bu 4 Sn, Bu 3 Sn(allyl) and Bu 3 SnPr but in the case of Bu 3 Sn(vinyl) the major fragment ions were Sn(vinyl) and SnH 2 (vinyl) . The major fragments formed are listed in Table 4.…”

“…The mass spectrum from phenyltripentyltin (Pe 3 SnPh) showed that the major fragmentation processes occur via formation of SnPh and SnPhH 2 ( Table 2) and not via the formation of PeSn and PeSnH 2 . As in all the other organotin compounds investigated in this study, the molecular ion for this compound was not detected.…”

Comparison of the tandem mass spectrometry analysis of compounds of general structure R2R?SnPh, RR?SnPh2 with R4Sn analogues

“…The same investigation also showed that for compounds of general formula R 3 SnR', where R = n-butyl or npentyl, the nature of the dihydride formed depends on R'. For example when R' = phenyl or vinyl the dihydride is R'SnH 2 and not RSnH 2 as in other species, such as Bu 3 SnAllyl. According to Chambers et al 4 the relative abundance of the hydride ion is related to the number of alkyl-tin bonds present in the molecule.…”