4. Conclusions
Direct analysis of primary amines in water by GC is hindered by the presence of free silanol groups in the pre-column. To date,no specific method dealing with this issue has been described.
In our study presented in this paper, we found some traditional methods used for deactivation of GC systems (injection of highly concentrated amine solutions, and deactivation of glass surfaces with DMDCS) not suitable for this purpose. Deactivation with ILs was successful, with [pmim][Tf2N] performing best. Because of the specific characteristics of its cations and anions, this IL acts as an excellent suppressor of unspecific adsorption of amines to the silica supports. As a result, it was possible to establish direct GC analysis of primary amines with RSD values lower than 6%. The detection limit for amines was 5 mM and for diamines it was reduced to 1 mM
(88 ppm for putrescine and 102 ppm for cadaverine). Furthermore,because of the thermal stability and negligible vapor pressure of the IL, the method is very robust with up to 400 injections per deactivation,and a total column lifetime of 5000 injections. Application of the method in a second GC system (Varian GC-430) was successful,
with a detection limit of 1 mM maintained and the number of injections per single deactivation increased to 800.