CARBOTEC FI

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THE HIGH SENSITIVITY EMITTER FOR FIELD IONIZATION MASS SPECTROMETRY

CARBOTEC Fl

The CARBOTEC Fl emitter has been
specially designed for the investiga-
tion of volatile substances by means
of Fl MS.
The CARBOTEC Fl shows very high
ionization efficiency in Fl MS and
thus offers a sensitivity which exceeds
that of the CARBOTEC ALLROUND even
by a factor of 3. Additionally, the
rate of fragmentation is reduced.

DURABILITY

The pure pyrocarbon microneedles of the CARBOTEC Fl can be used for several analyses in a row without loss of sensitivity. Cleaning of the emitter is carried out at an emitter heating current of 20 mA.

SENSITIVITY OF THE Fl MS ANALYSIS

The CARBOTEC Fl consists of a 5 µm tungsten wire with a coating of carbon microneedles of approx. only 20 µm in diameter (In Fl, the emitter does not have to serve äs a sample reservoir.). As a result, the average field strength of the Fl emitter is higher than that of the CARBOTEC ALLROUND (10 µm). Thus the onset voltage for Fl is only i kV for the CARBOTEC Fl in contrast to 2.5 kV for the CARBOTEC Allround. This results in a stronger ion emission current during analysis and therefore in greater sensitivity. However, the rate of fragmentation* in Fl MS is reduced by a factor of approx. 3 by the CARBOTEC Fl in comparison to the CARBOTEC ALLROUND.
 
The above becomes evident when comparing the Fl spectra of n-heptane recorded by the CARBOTEC ALLROUND (see spec. 1) and by the CARBOTEC Fl (see spec. 2) under otherwise equal conditions. Both spectra were recorded at a potential difference of 12 kV as single scan spectra. By using the CARBOTEC Fl, the intensity of the molecular ion in the Fl spectrum of n-heptane is raised by a factor of 3 in comparison to the CARBOTEC ALLROUND.
The CARBOTEC ALLROUND spectrum shows a ratio of the ethyl fragment ion (l 29) to the molecular ion (l 100) of 1.5 %.
 
However, the CARBOTEC Fl spectrum shows a ratio of the ethyl fragment ion (l 29) to the molecular ion (l 100) of only 0.4 %.
All in all, the CARBOTEC Fl allows Fl analyses which are more sensitive than analyses with the CARBOTEC ALLROUND by a factor of 3, whereas the rate of fragmentation is reduced by a factor of 3.
 
 
* The ratio of the ethyl fragment ion (l 29) to the molecular ion (l 100) is taken here as a measure of the rate of fragmentation.
 

 
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 Spec. 1: Fl spectrum of 2 x 10-5 mbar n-heptane recorded with the CARBOTEC ALLROUND at 12 kV (single scan).

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 Spec. 2: Fl spectrum of 2 x 10-5 mbar n-heptane recorded with the CARBOTEC Fl at 12 kV