Comparison of detection limits estimated using single- and multi-concentration spike-based and blank-based...

Area of Science:

• Environmental Chemistry
• Analytical Chemistry
• Water Quality Analysis

Background:

• Accurate estimation of detection limits (DLs) is crucial for environmental monitoring.
• Existing methods like the U.S. Environmental Protection Agency's (EPA) Method Detection Limit (MDL) have limitations.
• Comparing different DL estimation procedures is essential for reliable water sample analysis.

Purpose of the Study:

• To compare spike- and blank-based procedures for estimating detection limits (DLs) in water samples.
• To evaluate these procedures against EPA's MDL revisions 1.11 and 2.0.
• To assess the performance of ASTM Within-laboratory Critical Level (DQCALC) and EPA's Lowest Concentration Minimum Reporting Level.

Main Methods:

• Application of spike- and blank-based procedures for DL estimation.
• Comparison with EPA Method Detection Limit (MDL) procedures (revisions 1.11 and 2.0).
• Utilized DQCALC and EPA's Lowest Concentration Minimum Reporting Level for multi-concentration spike-based comparisons.

Main Results:

• Blank-based DLs (MDL_b99, MDL_bY) using numerous blank samples often achieve the desired ≤1% false positive risk.
• Spike-based procedures (DQCALC, MDL rev. 2.0) are necessary for organic methods lacking sufficient blank data.
• DLs are procedure-dependent and dynamic, best represented as a range, informed by both blank and spike methods.

Conclusions:

• Blank-based DL estimation is often superior for water samples, especially with large numbers of blanks.
• Spike-based methods are vital for specific analytical challenges, like organic analyses with limited blank data.
• DLs should be considered a dynamic range, not a static value, to accurately reflect analytical capabilities and minimize reporting risks.