The PTR-TOFMS and classic PTR-QMS series can include switchable reagent ions (PTR+SRI-MS), where instead of the single precursor ion
([H.sub.3]+) used in PTR-MS systems, NO+ and [O.sub.2]+ can be used to ionize trace constituents chemically in gas samples.
selection allows ions from complex mixtures or closely associated neighboring isotopic envelopes to be isolated and fragmented easily.
1, A and B, show the isotope distribution for the [(M+2H).sup.2+] precursor ion
for the naturally occurring peptide DYVSQFEGSALGK and the [D.sub.3]-leucine-labeled peptide, respectively.
The Analyst software incorporates enhanced stability for instrument control and data acquisition with added functionality for intelligent precursor ion
selection in MS/MS.
QuanTIS precursor ion
allows specific isolation of precursor ions
designated for MS/MS, thus achieving accurate and easy-to-interpret results.
The ion trap is not only used to focus ions before ejection into the TOE but also supports fragmentation, M[S.sup.n] analysis and a high precursor ion
selection (resolution >1000 at 1000 m/z).
With triple quadrupoles, SRM has implied that the precursor ion
is selected with a mass tolerance of [+ or -]0.5 m/z or higher.
Isotope-labeled peptides; the analytical internal standard (IS) DR[V [sup.13]C, [sup.15]N]YIHPFHL; the degradation standard (DS) DR[V [sup.13]C,[sup.15]N]Y[I[sup.13]C, [sup.15]N]HPFHL; and the DS DRVYIH[P [sup.13]C,[sup.15]N]FHL and DRVYI[H [sup.15]N] PF[H [sup.15]N]L used for precursor ion
and targeted selected reaction monitoring (SRM) studies were purchased from Sigma Life Sciences or Cambridge Isotope Laboratories.
If, for example, a precursor ion
of a target analyte in a pure solution exhibits an m/z ratio of 582 and gives rise to 2 major fragment ions by MS/MS, these 2 fragments will exhibit a characteristic fragment-intensity ratio (e.g., the fragment with an m/z ratio of 188 is 3 times more intense than a fragment with an m/z ratio of 210, yielding a 3:1 ratio).
For the acquisition of both [MS.sup.2] and [MS.sup.3] spectra, we set the precursor ion
isolation width at 2 and the collision energy at 45%.
During each infusion a precursor ion
scan from m/z 900 to m/z 990 was performed (30-s integration).