Using Procedural Blanks to Generate Analyte-Specific Limits of Detection for Persistent
Organic Pollutants Based on GC-MS Analysis
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Abstract
Several
methods are used to generate a limit of detection for organic
pollutants measured by gas chromatography–mass spectroscopy
(GC-MS); all have theoretical and practical drawbacks. The current
project investigated two common existing methods (statistical and
empirical) for applicability to chromatographic properties from real
samples, comparing these with a new proposed method using procedural
blanks to estimate a minimum detectable peak area. Weaknesses of all
three methods are discussed. The proposed method was superior to other
examined methods in that it provided analyte-specific limits of detection
linked to the recovery of mass-labeled internal standards for every
analyte within every sample. Other identified quality assurance benefits
included the following: enhanced protection against false positives;
providing a sensitivity performance metric across batch, analyst,
and instrument; enabling chemists with discretionary decisions specific
to every analyte regarding detectability and interferences; and some
strengths of both statistical and empirical techniques without major
drawbacks of either. In marine sediment samples, the proposed method
of calculating the limit of detection increased reporting of trace
level (low- to subppb) GC-MS data for polychlorinated biphenyls (PCBs),
polybrominated diphenyl ethers (PBDEs), organochlorine pesticides
(OCPs), and polycyclic aromatic hydrocarbons (PAHs) by up to 400%
compared with the statistical method