Using performance reference compounds to compare mass transfer calibration methodologies in passive samplers deployed...

Area of Science:

• Environmental Chemistry
• Analytical Chemistry
• Environmental Science

Background:

• Passive samplers are widely used to monitor environmental contaminants.
• Performance reference compounds (PRCs) are crucial for assessing passive sampler performance and estimating contaminant concentrations.
• Various methods exist to interpret PRC data and calculate freely dissolved concentrations (Cfree).

Purpose of the Study:

• To compare the precision and reproducibility of three common methods for estimating Cfree using PRCs.
• To evaluate the influence of passive sampler thickness on Cfree estimates.
• To provide guidance on selecting appropriate methods for passive sampling data analysis.

Main Methods:

• Low-density polyethylene strips loaded with PRCs and varying thicknesses were used as passive samplers.
• Samplers were deployed in the water column of New Bedford Harbor.
• Three methods (first-order kinetic, nonlinear least squares, diffusion) were applied to analyze PRC data and estimate Cfree.

Main Results:

• The nonlinear least squares and diffusion methods yielded the most precise Cfree estimates for PCBs, with statistically indistinguishable results.
• Relative standard deviations (RSDs) for total PCB measurements varied from 0.04% to 12% across methods and thicknesses.
• RSDs for estimates using the same method but different thicknesses ranged from 8% to 18%.

Conclusions:

• Environmental scientists and managers should consider using the nonlinear least squares or diffusion methods for estimating Cfree from passive sampling and PRC data.
• These methods offer improved precision and reliability in environmental monitoring.
• Understanding the impact of sampler thickness is important for accurate Cfree estimations.