3.2.3. Quantification using standard additions
The optimum response in terms of chromatographic selectivity
and highest signal to noise ratio was achieved using SIM at the
combined 124 and 109 masses. Peaks eluting in the SIM chromatogram
at the appropriate time (LRI 1899), were only identified as
guaiacol when MS peaks containing fragments at m/z 109 and
124 were presented at expected peak area ratios. Quantitative
measurements were made using integrated peak areas from the
109 + 124 m/z SIM. The amount of guaiacol in the samples was
determined from the linear regression equation of peak areas from
the standard addition experiments. Linear regression produced a
straight line with a slope value of 3499 area counts/lg/l and a correlation
coefficient of 0.991 (3499277.6, R2 = 0.9908). LOD,
limit of detection, calculations were based on this calibration function.
It was determined that the SPME GC/MS method used in this
study had an instrumental guaiacol limit of detection, LOD, value of
0.49 lg/l, with a signal noise ratio of 11.