Considering the low level of oleic acid and fatty acids to be
loaded onto the column, a splitless injection mode was chosen to
increase the method sensitivity. To avoid overloading the column,
the injection volume of 1 μL was selected. The boiling points of
oleic acid and related fatty acids are quite high with broad ranges
of 162–383 °C. The inlet temperature must balance the quick fatty
acid evaporation and the generation of a good peak shape. Three
inlet temperatures (210, 230 and 250 °C) were evaluated. At the
low inlet temperature of 210 °C, some fatty acids with high boiling
points could not be eluted due to lack of energy to vaporize. At the
high inlet temperature of 250 °C, the recoveries of saturated fatty
acids were better than 210 °C, but the peak areas of some unsaturated
fatty acids were decreased due to the thermal degradation.
Hence, the inlet temperature of 230 °C was chosen for
further study. No thermal degradation was observed at the inlet
temperature of 230 °C.