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Data qualifiers are used in lab reports to indicate a problem or irregularity with the analytical result. The most common qualifiers are shown here; most labs also will use footnotes to explain the qualifiers they have used.
J: The number is an estimated concentration because something in the sample interfered with the analysis.
U: The contaminant was not detected at a concentration greater than the detection limit.
UJ: The contaminant was not detected, but the detection limit is estimated because of interference from something in the sample.
R: The data are unusable. Resampling and reanalysis are necessary for verification.
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