However,
the LOD obtained is enough to detect the fluorine concentrations in toothpaste samples.
Also,
the characteristics of calibration curves as well as the analytical parameters given in Table 1 are not strict
because their values may vary for different set of experiments from day to day.
After optimization of experimental parameters,
the validity of the method was tested
by analysis of a spiked certified reference material SPS-NUTR WW2 (Table 2).
The certified concentration of fluorine in CRM could be determined in the uncertainty limits as well as the added concentrations could be recovered satisfactorily (Table 2),
which shows that the interference from the waste water matrix is not significant in the presence of 3000 mg L−1 of aluminum and fluorine concentration. However,
this does not mean that fluorine can always be determined by using linear calibration technique in all samples.