2.5. Method validation procedure
In order to evaluate quantitative analysis in this experiment,
spiking test was carried out concerning linearity, recovery, and
MDL. Calibration was conducted with five concentration points,
which are 0.5, 5, 10, 50, and 100 ng/g, respectively, to validate the
linearity of the standard spiked sample according to the sample
preparation methods described in Section 2.2.
The recoveries were estimated with a 5 g sample at the concentration
level of 50 ng/g. These were calculated from the ratio of
the peak area of target n-nitrosamine to the peak area of their
corresponding isotope labeled standard as shown in Table 1. MDLs
were measured by analyzing seven replicate samples spiking target
nitrosamine standards to the control blank samples at the
concentration of 10 ng/g in the cosmetic sample.