4.6. Calibration graph
Under the optimized experimental condition, the calibration
graph established for the phosphate determination in its concentration
range 0.5–10gml−1 is given in Fig. 6. It is having a straight
line with slope, 0.0126 and intercept, 0.0135. Molar absorptivity,
correlation coefficient and Sandell’s sensitivity values were calculated
and are found to be 1.712×10−3 mol−1 cm−1, 0.9769 and
0.0555gcm−2 respectively. The precision and accuracy of the
method were studied by analyzing 1.0, 2.5 and 5.0ppm phosphate
solutions. The precision of the method as expressed by the relative
standard deviation is found to be less than 3.2% whereas its
accuracy as expressed by the calculated relative error is 2.7%.