Table 2.
Comparison between observed and recommended concentrations of metals in international certified materials (Units: μg g−1).
| Reference materials | Metals (numbers) | Observed value | Recommended value | Bias (%)c) | ||
|---|---|---|---|---|---|---|
| m±2stda) | RSD(%)b) | m±2std | RSD(%) | |||
| SRM2711 | Cd(Nd)=8) | 40.7±2.33 | 2.92 | 41.7±0.25 | 3.00 | −2.40 |
| (soil) | Cu(N=8) | 112±11.4 | 5.20 | 114±2.0 | 0.90 | −1.75 |
| Pb(N=8) | 1,059±23.9 | 1.15 | 1,162±31 | 1.36 | −8.86 | |
| Zn(N=8) | 346±22.9 | 3.38 | 350±4.8 | 0.70 | −1.26 | |
| CRM281 | Cd(N=8) | 0.14±0.02 | 6.58 | 0.12±0.00 | 1.28 | +16.7 |
| (rye grass) | Cu(N=8) | 9.24±0.45 | 2.49 | 9.65±0.38 | 2.00 | −4.25 |
| Pb(N=8) | 2.45±0.47 | 9.82 | 2.38±0.11 | 2.36 | +2.94 | |
| Zn(N=8) | 26.9±2.69 | 5.09 | 31.5±1.4 | 2.27 | −14.6 | |
a)
Mean value ± 2 × standard deviation (95% confidence limit)
b)
RSD(%) (residual standard deviation) = (standard deviation / observed mean) × 100
c)
Bias (%) = {(observed mean – recommended mean) / recommended mean{ × 100
d)
Number of samples