Axis BTA 2100D Manual do Operador descarregar pdf (Página 222)

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Increase or decrease the CID (excitation) amplitude until a change in the spectra

is observed. In the case of nonresonant CID, use 10 volt steps; for resonant CID,

use 0.2 volt steps. Continue to increase or decrease the CID (excitation)

amplitude, but in smaller increments until suitable ion spectra are obtained.

Adjust the excitation time in 10-ms steps to optimize the spectra.

NOTE: If the parent ion is ejected instead of forming a product ion, increase the

excitation rf level from 48 to 55 m/z and adjust the CID (excitation) amplitude. In

general, increasing the rf storage level necessitates the use of a higher

amplitude to dissociate the ions. Do not, however, raise the excitation rf level

above the storage level of the product ions.

How to Customize the Resonant Excitation Method

Using a fixed sample source such as perfluorotributylamine (PFTBA) calibration

gas or the column bleed obtained by raising the gas chromatograph oven

temperature to 300C, follow these steps to customize the resonant excitation

method.

Reduce the modulation range to 0 steps. The modulation rate will now have no

effect on the spectra, i.e., the rf storage level is fixed. Iteratively adjust the CID

(excitation) amplitude and excitation time to optimize parent-to-product ion

conversion.

NOTE: If the amplitude used is sufficiently large, the parent ion should be

ejected. Parent ion ejection indicates that the CID frequency applied to the end

caps is properly resonant and that the trap function has been correctly calibrated.

Increase the modulation range to 2 steps.

Alternatively, increase the CID bandwidth by increasing the Number of

Frequencies from 1 to 3 frequencies. This increases the mass range around the

parent ion that is excited. Several frequencies may be used with or without

modulation, and may be useful when exciting isotopic clusters.

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