- P-ISSN 1225-0163
- E-ISSN 2288-8985
The study was carried out to confirm the reliability of standard samples, low concentration <TEX>$0.74mgN(NO_3)/l$</TEX>, <TEX>$0.58mgF^-/l$</TEX>, high concentration <TEX>$2.14mgN(NO_3)/l$</TEX>, <TEX>$1.25mgF^-/l$</TEX>, on the base of quality control chart. The analytical results had the precise reliability with standard deviation of 0.010, 0.017, 0.056 and 0.019, respectively. When three persons A, B and C, who had different analytical experiences, analyzed the standard samples six times repeatedly, C person, who had more academic career and analytical experience, produced far better reliability for analytical results. Therefore, these standard samples were very suitable for external quality control test, because all persons' average values for analytical results were close to the values of prepared standard samples.