Axis BTA 2100D Manual do Operador descarregar pdf (Página 162)

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Prescan Ionization Time

Prescan Ionization Time parameter as used in MS/MS applications is set to 200

sec.

Default Parameters for Reagent Gases used in Chemical Ionization Mode

Reagent Gas Methane Isobutane Ammonia

Maximum Ionization Time

(sec)

2000 2000 2000

Maximum Reaction Time

(msec)

60 60 60

CI Storage Level (m/z) 13 19 13

CI Background Mass (m/z) 45 65 40

Ejection Amplitude (v) 9.0 15 9

Using Non-Standard CI Reagent Gases

Gases other than methane, ammonia, or isobutane can be used successfully

with the Saturn GC/MS. If you are using a non-standard CI reagent gas, you

need to select the Reagent Gas list item labeled "User Defined". Then you will

need to input the name of the gas and the values for the CI parameters; the

parameter values will not be set up automatically.

NOTE: When you install a new supply of a non-standard reagent gas, you must

adjust the reagent gas pressure. After the pressure has been adjusted properly,

you should check the pressure at least once every day if you plan to operate in

CI on a daily basis. For procedures to adjust and check the pressure of a non-

standard reagent gas, please contact a Customer Support Representative.

How to Optimize the CI Background Mass

The proper setting for the CI background mass eliminates reagent ions which are

left over after the reaction period.

With the CI reagent connected and properly adjusted, click the CI Gas control on

the System Control Manual Control page to open the CI gas valve solenoids.

Turn on the trap and observe the spectrum over the scan range specified in the

acquisition method, (don’t use adjust CI Gas). Look for any ions at the low end of

the range. The figure below shows an acetonitrile spectrum with the CI

background mass set too low (=50 m/z). The 54 ion is clearly visible and has

caused a reduced ionization time. The next figure shows a proper background

mass setting for the same conditions (=65 m/z).

1 2 ... 157 158 159 160 161 162 163 164 165 166 167 ... 596 597

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