of mass spectra with standards (Mainlab, Replib and Tutorial
data of GC–MS systems). The reference compound, nicotine
was used as marker. The marker was accurately weighed and
dissolved in methanol to produce a series of concentrations.
Standard calibration curves were established by plotting the
peak areas against different concentrations of the reference
compounds (varying from 5.0 to 1000 ng on column for nicotine).
The external standard method was used for quantification
of the marker in the samples of leaves extract from
different places.
The system suitability of the method was evaluated by the intra-
and inter-day precision and accuracy of replicates. The accuracy
was evaluated through recovery studies by adding known
amounts of the standard solution to the extract. Controls from
all samples were prepared and analyzed. The recovery experiment
was performed at three different standard concentrations.