Chemistry Reference
In-Depth Information
Figure 2.
Acetonitrile/ H
2
O mobile phase, column temperature 35
o
C
In this work, water and acetonitrile with 0.1% acetic acid were used for all liquid
chromatographic separations. No buffers were used. Two types of additives have been
added to the mobile phase that is acetic acid and formic acid during optimization and it was
found that by adding 0.1% of acetic acid gives better resolution than formic acid. The results
are also more stable. The additive was added to improve the chromatographic shape and to
provide a source of protons in the reversed phase and to enhance and control the formation
of ions. A study on water:methanol with both 0.1% acetic acid and formic acid was also
done but it did not give good resolution and the results are not reproducible.
The reversed phase solvents are installed on the channels A and C. Channel A is the
aqueous solvent (water) and channel C is the organic solvent (acetonitrile). Silica dissolves
at high pH, therefore it is not recommended to use solvents that exceed pH7. The pH for
acetonitrile was in the range of pH 2.5 - pH 3.5.
Figure 3.
Chromatogram of triazole standards mixture at 0.5 µg/mL
3.2. Mass spectrometry
Prior to triazole analysis, the chromatographic parameters including the heated nebuliser
parameters were optimized. LCMS infusion was carried out to examine the ionization and
fragmentation patterns of the analytes. The APCI source was used in the positive ion mode.
A full scan was used for the MS optimization and a selected ion monitoring (SIM) was used
for the monitoring of the selected ion. Table 1 showed the triazoles and quantitation ion.
