Equation of calibration curve R2 LOD, mg/L LOQ, mg/L
  System I
PMT   y=(0.1870 ± 0.0005)x+(0.300 ± 0.002) 0.9998 2.93 9.76
TD   y=(0.0480 ± 0.0002)x-(0.1760 ± 0.0004) 0.9990 2.34 7.82
CPM   y=(0.0980 ± 0.0004)x-(0.584 ± 0.001) 0.9990 1.93 6.45
  System II
PMT   y=(0.1080 ± 0.0005)x-(0.298 ± 0.001) 0.9998 2.70 9.01
TD   y=(0.1600 ± 0.0007)x-(1.267 ± 0.001) 0.9998 2.39 7.97
CPM   y=(0.1290 ± 0.0006)x+(0.925 ± 0.001) 0.9998 2.67 8.90
  System III
PMT   y=(0.1800 ± 0.00030)x-(1.048 ± 0.006) 0.9975 3.00 9.99
TD   y=(0.1650 ± 0.0008)x-(1.277 ± 0.002) 0.9998 2.69 8.98
CPM   y=(0.1570 ± 0.0008)x-(1.073 ± 0.002) 0.9998 2.60 8.66
Table 2: The statistical parameters of calibration curves.