In some situations data will be reported with a qualifier.
The following is a listing of EPA Data Qualifiers used for HRMS results. These are used to flag analytes in an analytical report and in EDD's (electronic data deliverable) under the column for data qualifiers. These flags or qualifiers give additional information to support the data point.
Below is a listing of the common data flags / data qualifiers used.
U - Indicates compound was analyzed for, but not detected. The calculated concentration, in this instance is the Estimated Detection Limit (EDL) and must be calculated based on the signal-to-noise (S/N) ratio. This calculation takes into account the sample weight/volume extracted, the volume of the most concentrated extract, the injection volume, and dilution of the most concentrated extract prior to analysis.
J - Indicates an estimated value. This flag is used when the mass spectral data indicate the presence of an analyte meeting all the identification criteria, but the result is less than the Reporting Detection Limit (RDL) and greater than the Estimated Detection Limit (EDL).
B - This flag is used when the analyte is found in the sample, as well as in the associated blank. It indicates possible/probable blank contamination and warns the data user to take appropriate action. From the laboratory perspective the sample set should be re-extracted, if possible, to eliminate the blank contamination.
Q – One or more quality control criteria failed (e.g., LCS recovery, surrogate spike recovery or CCV).
E - This flag identifies analytes whose concentrations exceed the calibration range of the HRGC/HRMS instrument for that specific analysis. If one or more compounds have a response greater than full scale, a smaller sample size must be extracted and analyzed if possible. All such compounds with a response greater than full scale should have the concentration flagged 'E' for the original analysis.
If a result is reported at the EDL (in the case of HRMS) or at the MDL (for non-HRMS) then it would have a 'U' flag.
If a results is reported between the EDL (or MDL) and the RDL then it would be flagged with a 'J'.
If a result is reported at the CS1 level (lowest calibration standard) or up to the CS5 level (highest calibration standard) then there is no associated flag.
If a result is reported at > the CS5 level then it would have an 'E' flag.
If compound X in the CCV is outside the acceptable limits then compound X in all the samples would be flagged with a 'Q'. Same would apply if a surrogate or LCS (blank spike) recovery was outside the acceptable criteria.
If compound X was found in the blank then compound X would be flagged with a 'B' in all the samples.