Electron Ionisation and Chemical Ionisation
EI and CI analyses are generally performed on the MAT95 magnetic sector low molecular weight, volatile, for metal-containing species, and when there are special sample requirements, e.g. air sensitive or insoluble samples.
EI: Source temperature 200 °C; electron energy 7 0eV; mass range m/z 33-650 unless higher is requested.
CI: vary with application - available on request; mass range m/z 33-650 unless higher is requested.
- Mass resolution is set to at least 400 greater than the maximum mass (10% valley definition);
- Solids probe or desorption probe may be used, with manually controlled heating rates.
- EI: source temperature 120 °C to 200 °C; electron energy 70eV; mass range as required by analyte;
- CI+ or CI-: source temperature 120 °C to 160 °C; mass range as required by analyte; ammonia or methane reagent gas.
Accurate mass Electron Ionisation (EI) and Chemical Ionisation (CI) measurements, in positive ionisation mode, are obtained
on the MAT95 by "peak matching", with mass resolution between 8000 and 10000 (10%
valley definition). For EI, Heptacosa (perfluorotributylamine) is the usual reference compound for accurate mass measurement, and for CI, PEG (polyethyleneglycol) is usually used. If a different reference compound is used, it will be specified in an attachment to the result. Precision of the method is better than 5ppm
and nearly always within 3 ppm. Usual mass range is 50 to 1000 Da but higher
is possible; measurements of molecular masses over 1000Da are usually
discouraged as being a meaningless exercise.
EI electron energy 7 0eV; either the water-cooled or desorption probe is used, as required; source temperature depends on sample.
CI source temperature ca. 140 °C and electron energy 50eV; either the water-cooled or desorption probe is used, as required.
Finnigan MAT 95 XP
High resolution double focussing (BE) mass spectrometer EI, CI, LSIMS, ESI and APCI capability.
- Mass Range: m/z 3,500 at full accelerating voltage;
- Maximum Resolution: 60,000.
Commercial supplier: Finnigan MAT (a subsidiary of Thermo Scientific Scientific)