Patterns of microparticles in blank samples: A study to inform best practices for microplastic analysis

Area of Science:

• Analytical Chemistry
• Environmental Science

Background:

• Quality assurance and quality control (QA/QC) are vital for accurate microplastic analysis.
• Procedural blanks are essential for quantifying background contamination but are inconsistently used.
• Variability in blank acquisition and data reporting hinders microplastic research.

Purpose of the Study:

• To evaluate laboratory procedural blanks for microplastic quantification and characterization.
• To inform and improve QA/QC procedures in microplastic analysis.
• To assess the effectiveness of common contamination control methods.

Main Methods:

• Collected and analyzed procedural blanks from 12 participating laboratories.
• Investigated contamination levels, including particle count, color, morphology, and size.
• Evaluated the impact of various QA/QC techniques (air filtration, filtered water, enclosed environments).
• Tested different blank subtraction methods.

Main Results:

• Procedural blanks contained significant microplastic contamination (mean 80 particles/sample), predominantly black fibers (20–212 µm).
• Common QA/QC techniques did not significantly reduce blank contamination.
• No clear pattern was observed based on total recovery when testing subtraction methods.
• Particle characteristics varied, with few particles <20 µm detected, possibly due to detection limits.

Conclusions:

• Standard QA/QC methods are insufficient to eliminate microplastic contamination in procedural blanks.
• Blank subtraction using a combination of particle characteristics (color, morphology, size) is recommended for representative results.
• Further research is needed on other QA/QC parameters, including different blank types and detection limits.