Table 3.
The precision of measured concentrations of 232Th for QC and spiked urine materials (ng/L)
| Sample | N (number of runs) | Average concentration (ng/L) | SD | RSD (%) | Target value c (ng/L) | Bias (%) |
|---|---|---|---|---|---|---|
|
| ||||||
| Low QCa | 60 | 47.2 | 2.68 | 5.7 | 50 | −5.6 |
| High QCa | 60 | 741 | 31.0 | 4.2 | 750 | −1.2 |
| Pool-1b | 16 | 39.1 | 1.6 | 4.1 | 40 | −2.3 |
| Pool-2 b | 16 | 194 | 4.1 | 2.1 | 200 | −3.0 |
a
Internal quality control material made at CDC by spiking certified reference material in pooled urine collected anonymously
b
Urine materials made at CDC by spiking certified reference material into pooled urine collected anonymously
c
Target values of spiked QCs and urine pools using NIST traceable certified reference material from High Purity Standards (Charleston, SC) and Inorganic Ventures (Christiansburg, VA)