Voyager DP-263-S Guía de usuario Pagina 446

  • Descarga
  • Añadir a mis manuales
  • Imprimir
  • Pagina
    / 612
  • Tabla de contenidos
  • SOLUCIÓN DE PROBLEMAS
  • MARCADORES
  • Valorado. / 5. Basado en revisión del cliente
Vista de pagina 445
Chapter 7 PSD Analysis
7-42 PerSeptive Biosystems
7
Observing prompt
and PSD
fragments
When operating under conditions that yield high resolution for
angiotensin I, and when the Precursor Ion Selector is turned
off, you should observe the following:
Prompt fragments—Well-resolved fragment ions
generated in the source before acceleration. The sharp
peak at 1,181.7 Da is the y9 ion.
Prompt fragments appear at the expected mass in
reflector mode because their flight time is the same as a
molecular ion of the same mass accelerated from the
source. They do not appear at the expected mass in PSD
mode.
PSD fragments—A poorly-resolved peak cluster that is a
mixture of the y9 fragment (1,181.7 Da) and the b9+H
2
O
fragment (1,183.6 Da). PSD fragments are generated in
the flight tube after acceleration.
PSD fragments appear at a higher mass than expected in
a reflector-calibrated spectrum. They appear at the
expected mass in PSD mode. See “PSD fragment ions
on page 7-3. These higher than expected masses are
corrected in PSD calibration when you generate the
composite spectrum.
Effect of
Precursor Ion
Selector on
prompt and PSD
fragments
Even if prompt and PSD fragments are identical in chemical
structure, they will travel down the flight tube at different times
(Figure 7-13):
Prompt fragments—Accelerated based on their initial
fragment mass, and reach the reflector sooner than their
corresponding PSD fragments.
PSD fragments—Accelerated based on the mass of the
molecular ion from which they form, and reach the
reflector later than the prompt fragments.
Because of this difference in flight times, the Precursor Ion
Selector can screen out prompt fragments while allowing PSD
fragments to pass into the reflector.
Vista de pagina 445
1 2 ... 441 442 443 444 445 446 447 448 449 450 451 ... 611 612

Comentarios a estos manuales

Sin comentarios