The calcium and magnisium ions determination was carried out using a Perkin-Elmer (Optima 2100 DV, Norwalk, CT, USA) inductively coupled plasma atomic emission spectrometer (ICP-AES) instrument connected with an AS 93 Plus auto-sampler.
The 40-MHz free-running generator was operated at a forward power of 1300 W; the outer, intermediate and Ar carrier gas flow rates were 15.0, 0.2 and 0.8 L/min, respectively.
The pump flow rate was 1.5 ml/min.
The carrier gas flow rate was optimized to obtain maximum signal-to-background ratios HANNA pH-meter was used to measure the pH after calibration with standard pH tablets of pH 4, 7, and 9.