Overview
ISO 24261-2:2021 - "Fine bubble technology - Elimination method for sample characterization - Part 2: Fine bubble elimination techniques" specifies standardized techniques to remove fine uncoated bubbles from aqueous dispersions and how to optimize those procedures to maximize elimination efficiency. The document applies only to fine bubbles without shells (not to coated bubbles) and supports accurate sample characterization by distinguishing bubbles from solid/liquid contaminants.
Key topics and technical requirements
- Elimination techniques covered
- Ultrasonication (recommended frequency > 430 kHz; avoid direct immersion of oscillators/probes into samples)
- Ultracentrifugation (system configuration, selectable parameters and optimization)
- Freeze and thaw
- Boiling and cooling
- Measurement and optimization principles
- Tune and optimize conditions (e.g., frequency, driving power, irradiation time for ultrasonication) to maximize elimination efficiency.
- Optimize by measuring size and number concentration indices before and after elimination to assess effectiveness.
- Sample and environment requirements
- Use cleaned generation systems and clean gas (air, N2, O2). Samples must not contain stabilizing agents (surfactants).
- For high-accuracy work, ISO Grade 1 water (ISO 3696) is recommended for generation; ISO Class 7 air cleanliness (ISO 14644-1) is suggested for generation and measurement environments.
- Measurement instrument guidance
- Instruments should quantify total number concentration and total volume concentration across relevant size ranges; multiple complementary techniques (e.g., particle tracking analysis and laser diffraction) can be used.
- Documentation & reproducibility
- Key variables (device model/power, container type, sample volume, tank and vessel geometry, positioning) must be specified to ensure reproducible results.
Practical applications and users
ISO 24261-2 is relevant to:
- Laboratories and test houses characterizing fine bubble dispersions
- Manufacturers of fine bubble generators and ultrasonic/centrifugation equipment
- Water treatment, aquaculture, agriculture, cleaning and biomedical R&D teams validating bubble generation performance
- Accreditation bodies developing measurement protocols for fine bubble products
Practical benefits include improved ability to separate bubbles from particulates for accurate size/concentration indices, standardized optimization of elimination procedures, and comparable inter-laboratory results.
Related standards
Keywords: ISO 24261-2:2021, fine bubble elimination techniques, ultrasonication, ultracentrifugation, sample characterization, fine bubble technology, elimination efficiency.