Frequent Questions

Can you clarify the quality control (QC) requirements for SW-846 Method 9060A, Total Organic Carbon (TOC)?

Can you clarify the QC requirements for TOC Method 9060A?

Section 7.6 states, "Quadruplicate analysis is required. Report both the average and range." Is the definition of "quadruplicate" analysis: four complete analyses of the same field sample, with analyses meaning separate "injections/aspirations" of the sample? Is this definition correct?

Section 8.3 states, "Verify calibration with an independently prepared check standard every 15 samples." Does this frequency mean 15 samples analyzed in quadruplicate (i.e., every 60 injections/aspirations – 15 samples times 4 injections/aspirations)? Or does it mean every 15 injections/aspirations (i.e., every 3.75 quadruplicate sample analyses)?

Would the QC samples (i.e., Laboratory control sample (LCS), Matrix spike/spike duplicate (MS/MSD), Calibration verifications (CCV), Instrument blanks (CCB) analyzed in a typical "CCV/CCB" set) also require quadruplicate analyses?

 

The four replicate analyses are obtained through four injections from a single field sample, and make up a single analysis for that sample. The arithmetic mean concentration is reported as the analyte concentration in the sample, and the calculated standard deviation on the mean from the replicate analyses is used as a QC diagnostic.

Calibration verification frequency should be based on the number of unique samples analyzed (not including duplicates of the same sample). This criterion refers to the analysis of 15 field samples, as well as to the analysis of QC samples; i.e., matrix spike samples, duplicate spike samples, field duplicate samples, and/or equipment blank samples. Thus, if 13 field samples + 2 QC samples are analyzed, the calibration verification standard must be run next.

QC samples should be analyzed in the exact same manner as the field samples. This includes the LCS, MS/MSD, initial or continuing calibration verification (ICV or CCV), and continuing calibration blank (CCB), etc. So, if the field samples are analyzed in quadruplicate, the QC samples should also be analyzed in quadruplicate.

Other category: QA/QC

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