respectively. The graphs obtained are presented in Figs. 3 and 4,respectively. Similarly, the influence of phosphate in the concentration: 0.20, 0.50, 1.00, 2.00 and 5.00 mg L1 on the signals of silicate in the range of 0.0–5.0 mg L1 was studied.
As seen in Figs. 3 and 4, significant influence of silicate on signals measured for phosphate (peak area and signal A1, respectively) was observed, but the signal measured for silicate was not influenced by phosphate at the studied concentration range
because a set of five analytical curves of nearly identical parameters was obtained. Therefore, to make possible simultaneous determination of both analytes, two-component calibration procedure based on four standard solutions containing the phosphate
and silicate in concentrations established in accordance with 22
factorial design [19] was applied