Objective To evaluate the uncertainty in measurement model of dichloroacetic acid and trichloroacetic acid in drinking water by gas chromatography.
Methods According to the Evaluation and Expression of Uncertainty in Measurement (JJF 1059.1-2012), a mathematical model was built to calculate the content of dichloroacetic acid and trichloroacetic acid in drinking water, and the sources and magnitudes of uncertainty in measurement were analyzed to evaluate the uncertainty in determining the content of dichloroacetic acid and trichloroacetic acid in drinking water.
Results When the content of dichloroacetic acid and trichloroacetic acid in drinking water was 0.010 8 and 0.003 83 mg/L, respectively, the relative extended standard uncertainties were 0.002 8 and 0.000 62 mg/L, respectively, at a confidence level of 95% and a coverage factor of 2.
Conclusion The curve fitting residual is the major source of uncertainty in gas chromatography-based measurement of dichloroacetic acid and trichloroacetic acid in drinking water.Rational selection of standard substance and accurate preparation of standard solution are key steps for a good standard curve.
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