The elimination of interference effects of the matrix on
magnesium determinations was necessary. A lanthanum salt
has been suggested as a matrix modifier [17]. In the present
work, lanthanum and strontium salts in different concentrations
were used. The results of the recovery tests are shown
in Table 2. As reported earlier, lanthanum was found to be
the more effective releasing agent for magnesium determinations,
but strontium was also effective. The optimum concentration
of strontium was found to be 2500 mg l−1. A limit
of detection of 2.5 mg l−1 and a limit of quantification of
8.3 mg l−1 were found under the optimised conditions using
strontium as the releasing agent