EPA Data Qualifiers

Analytical testing dots

The following is a list of EPA Data Qualifiers by category. These are used to flag analytes in an analytical report, under the column labeled "Q" for qualifier. A contractor or client may use additional flags as needed, but the definition of such flags must be explicit, not contradict the qualifiers listed below, and be included in the accompanying SDG Narrative, according to EPA instructions. This information is from the EPA Contract Laboratory Program (CLP).

 

PCB Congeners, Dioxins and Furans

Qualifier (flag) Definition
U Indicates compound was analyzed for, but not detected. The "CONCENTRATION" column is left blank in this instance, and an Estimated Detection Limit (EDL) must be calculated based on the signal-to-noise (S/N) ratio, as described in Exhibit D. 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 in Exhibit D, but the result is less than the Contract Required Quantitation Limit (CRQL), as listed in Exhibit C, but greater than zero.
B This flag is used when the analyte is found in the associated blank, as well as in the sample. It indicates possible/probable blank contamination and warns the data user to take appropriate action.
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 fullscale, except as noted in Exhibit D, a smaller sample size must be extracted and analyzed according to the specifications in Exhibit D. All such compounds with a response greater than full scale should have the concentration flagged "E" on the Form I for the original analysis. If the dilution causes any compounds identified in the first analysis to be below the calibration range in the second analysis, the results of both analyses shall be reported on separate copies of Form I. The Form I for the diluted sample shall have the"DL" suffix appended to the EPA Sample Number.
D This flag indicates all compounds identified in an analysis at a secondary dilution factor. If a smaller sample size is analyzed, as in the "E" flag above, the "DL" suffix is appended to the EPA Sample Number on the Form I for the diluted sample, and all concentration values reported on that Form I are flagged with the "D" flag. This flag alerts data users that any discrepancies between the concentrations reported may be due to dilution of the sample extract.
H This flag indicates that the analyte in question was quantitated using peak heights rather than peak areas for both the analyte and its internal standard.
X Other specific flags may be required to properly define the results. If used, they must be fully described, and such description must be attached to the Sample Data Package and the SDG Narrative. Begin using "X". If more than one flag is needed, use "Y" and "Z" as needed. The laboratory-defined flags are limited to the letters "X", "Y", and "Z".

 

Inorganics

Qualifier (flag) Definition
"C" Concentration qualifier
J The reported value was obtained from a reading that was less than the CRQL but greater than or equal to the MDL (Method Detection Limit).
U If the reading was less than the MDL.
"Q" qualifier
E The reported value is estimated due to the presence of interference. An explanatory note shall be included under “Comments” on the Cover Page (if the problem applies to all samples), or on the specific Form IA-IN or Form IB-IN (if it is an isolated problem).
N Spiked sample recovery not within control limits.
* Duplicate analysis not within control limits.
D The reported value is from a dilution.
"M" (Analysis Method) qualifier
P ICP-AES
MS ICP-MS
CV Manual Cold Vapor Atomic Absorption (AA)
AV Automated Cold Vapor AA
AS Semi-Automated Spectrophotometric
C Manual Spectrophotometric
" ": Where no data have been entered
NR The analyte is Not Required to be analyzed

 

Organics

Qualifier (flag) Definition
U This flag indicates the compound was analyzed for but not detected. The Contract Required Quantitation Limit (CRQL) shall be adjusted according to the equation listed in Exhibit D. CRQLs are listed in Exhibit C.
J

This flag indicates an estimated value. This flag is used when:

  1. estimating a concentration for Tentatively Identified Compounds (TICs) where a 1:1 response is assumed;
  2. the mass spectral and Retention Time (RT) data indicate the presence of a compound that meets the volatile and semivolatile GC/MS identification criteria, and the result is less than the adjusted CRQL but greater than zero
  3. the RT data indicate the presence of a compound that meets the pesticide and/or Aroclor identification criteria, and the result is less than the adjusted CRQL but greater than zero. For example, if the sample's adjusted CRQL is 5.0 μg/L, but a concentration of 3.0 μg/L is calculated, report it as 3.0J.
N This flag indicates presumptive evidence of a compound. This flag is only used for TICs, where the identification is based on a mass spectral library search and must be used in combination with the J flag. It is applied to all TIC results. For generic characterization of a TIC, such as chlorinated hydrocarbon, or for an "unknown" (no matches $ 85%), the "N" flag is not used.
P This flag is used for pesticide and Aroclor target compounds when there is greater than 25% difference for detected concentrations between the two GC columns (see Form X). The lower of the two values is reported on Form I and flagged with a "P". The "P" flag is not used unless a compound is identified on both columns.
C This flag applies to pesticide and Aroclor results when the identification has been confirmed by GC/MS. If GC/MS confirmation was attempted but was unsuccessful, do not apply this flag; use a laboratory-defined flag instead (see the X qualifier).
B This flag is used when the analyte is found in the associated method blank as well as in the sample. It indicates probable blank contamination and warns the data user to take appropriate action. This flag shall be used for a TIC as well as for a positively identified target compound.
E This flag identifies compounds whose response exceed the response of the highest standard in the initial calibration range of the instrument for that specific analysis. If one or more compounds have a response greater than the response of the highest standard in the initial calibration, the sample or extract shall be diluted and reanalyzed according to the specifications in Exhibit D. Exceptions are also noted in Exhibit D. All such compounds with responses greater than the response of the highest standard in the initial calibration shall have the result flagged with an "E"on Form I for the original analysis. The results of both analyses shall be reported on separate copies of Form I. The Form I for the diluted sample shall have "DL" suffix appended to the Sample Number.
D If a sample or extract is reanalyzed at a DF greater than 1 (e.g., when the response of an analyte exceeds the response of the highest standard in the initial calibration), the DL suffix is appended to the Sample Number on Form I for the more diluted sample, and all reported concentrations on that Form I are flagged with the "D" flag. This flag alerts data users that any discrepancies between the reported concentrations may be due to dilution of the sample or extract.

 

Other Abbreviations

symbol Definition
MDL Method Detection Limit
DL Dilution
CRQL Contract Required Quantitation Limit
TIC Tentatively Identified Compounds
RT Retention Time
GC/MS Gas chromatograph / mass spectrometer

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