Shimadzu has released a chemical ionisation technique for GCMS that significantly reduces running costs and improves laboratory safety
Principle of SMCI
The new soft ionisation method from Shimadzu, called Solvent Mediated Chemical Ionisation (SMCI) enables chemical ionisation without reagent gases like methane, isobutane or ammonia.
Instead, the headspace from common solvents, such as methanol or acetonitrile is mixed with an inert gas and carried into the ion source. The solvent molecules are ionised, which then causes chemical ionisation of the target molecules via protonation.*
The technique is highly effective for a large number of compounds and can give the same results as traditional CI, making it ideal for structural elucidation via the molecular weights. It can also provide further structural information, such as position of double bonds in unsaturated fatty acids using GC-MS/MS.
In many cases, the ionisation energy of EI is too high to verify molecular weights. Soft ionisation provides a suitable alternative to enable molecular weight information to be obtained. SMCI offers CI-like spectra to give analysts greater information about the structure and identity of compounds.