The hidden toxicity of solid phase extraction blanks in water analysis

Area of Science:

• Environmental Chemistry
• Analytical Chemistry
• Ecotoxicology

Background:

• Non-toxic blank samples are essential for Effect Directed Analysis (EDA) to distinguish environmental contaminants from procedural artifacts.
• Wastewater solid phase extraction (SPE) blanks unexpectedly exhibited toxicity in algae, daphnia, and in vitro assays.

Purpose of the Study:

• To identify the sources of toxicity in SPE blank samples.
• To develop strategies for remediating toxic occurrences in blank samples for accurate EDA.

Main Methods:

• Investigated toxicity of SPE elution solvents (methanol, ammonium hydroxide, formic acid).
• Analyzed metal ion release from SPE materials and system components.
• Evaluated alternative blank preparation methods using artificial freshwater.
• Assessed toxicity of different SPE materials (GCB, HLB, ENV+) before and after washing.

Main Results:

• Elution solvents, particularly ammonium and formic acid, were major toxicity contributors.
• Formic acid leached toxic metals (Cu, Zn) from SPE materials, impacting daphnia.
• Washing SPE materials and using artificial freshwater significantly reduced blank sample toxicity.
• Plasticizers from system components were detected at non-toxic levels.

Conclusions:

• Optimizing SPE elution solvents and thoroughly washing SPE materials are critical for non-toxic blanks.
• Using artificial freshwater for blank preparation further minimizes procedural contaminants.
• These modifications ensure the reliability of Effect Directed Analysis in environmental studies.