Research Article
High-Accuracy Determination of Potassium and Selenium in Human Serum by Two-Step Isotope Dilution ICPMS
Table 6
Sources of uncertainty in the determination of Se.
| Sources of uncertainty | Se | Level 1 | Level 2 | Level 3 | Value (xi) | uc (xi) | Value (xi) | uc (xi) | Value (xi) | uc (xi) |
| Type A uncertainties | RY | 0.020 | 0.0011 | 0.021 | 0.0013 | 0.024 | 0.0018 | Rz | 2.2 | 0.010 | 2.2 | 0.011 | 2.1 | 0.011 | RBc | 1.1 | 0.0053 | 1.0 | 0.0032 | 0.96 | 0.0042 | RB | 0.98 | 0.011 | 1.1 | 0.011 | 0.89 | 0.011 | CB/ | 1.4 | 0.37 | 1.4 | 0.37 | 1.4 | 0.37 | K | 1.0 | 0.0068 | 1.0 | 0.0068 | 1.0 | 0.0068 |
| Type B uncertainties | Cz/μg kg−1 | 5.6 × 102 | 3.0 | 5.0 × 102 | 2.6 | 5.2 × 102 | 2.8 | mzc/mg | 7.1 × 102 | 0.040 | 7.0 × 102 | 0.040 | 7.5 × 102 | 0.040 | mYc/mg | 2.9 × 102 | 0.040 | 2.9 × 102 | 0.040 | 2.5 × 102 | 0.040 | mY/mg | 1.0 × 102 | 0.040 | 1.0 × 102 | 0.040 | 1.1 × 102 | 0.040 | mx/mg | 1.2 × 103 | 0.040 | 1.0 × 103 | 0.040 | 9.0 × 102 | 0.040 | Combined type A and type B | — | 2.5 | — | 3.4 | — | 4.2 | Degrees of freedom (Veff) | | 5 | | 5 | | 5 | Coverage factor (k) | | 2 | — | 2 | — | 2 | Measured value/mg kg−1 | 80.6 | — | 115.9 | — | 133.8 | — | Expanded uncertainty (U ()) | 1.5 | 2.0 | 2.6 |
|
|