A small error in quantitative measurement or invalidation of microbiological test results can stem from microscopic chemical residue adhering to the walls of old test tubes. This is a major headache for many testing centers today.

For Quality Managers and Lab Managers, meeting international technical requirements when cleaning auxiliary equipment is always a top priority. We need to establish a standardized procedure to completely eliminate the risk of interfering contaminants.

This article provides detailed instructions on the process of handling and cleaning glass/plastic equipment to fully meet the international standard ISO 17025. The advanced technical solution below will help your system pass the audit perfectly.

1. Instrument Contamination Control According to ISO 17025

1.1 Facility Environmental Risk Management

The design and management of the facility environment is a prerequisite for protecting the accuracy of all physicochemical analyses. According to the strict requirements in Section 6.3.4 of the national standard TCVN ISO/IEC 17025:2017, laboratories must implement facility control measures. This process is monitored periodically to prevent contamination, interference, or direct adverse effects on laboratory operations.

Contamination from suspended particulate matter, microorganisms, or residual chemicals from previous batches can seriously alter the physico-mechanical properties of the test sample. Therefore, effective separation between areas with incompatible laboratory operations is mandatory. Isolating the contaminated instrument handling area eliminates the risk of convection currents causing cross-contamination.

1.2 Responsibility for Maintaining Auxiliary Equipment

Glassware, plasticware, or consumables used in experiments are all identified as components of the laboratory equipment system. Therefore, Section 6.4.3 requires us to establish documented procedures for the handling, transport, storage, use, and maintenance of equipment. This process ensures the proper functioning of auxiliary equipment and prevents contamination or mechanical damage.
Each tester is responsible for maintaining the integrity of the measuring equipment before and after performing reactions. If acid or alkali deposits on the equipment are not treated according to the maintenance schedule, the volumetric accuracy will be compromised. Therefore, adherence to the SOP for cleaning auxiliary equipment is mandatory to maintain the usability of the measurement results.

2. Procedure for verifying the cleanliness of glassware

2.1 Visual and chemical inspection methods

To demonstrate technical competence before ISO IEC 17025 assessment teams, you need to build objective evidence for the cleaning step. Applying the provisions of Section 3.8, the verification procedure is mandatory to prove that the object fully meets the requirements. Technicians are not allowed to return the equipment to operation without cleanliness verification.
The continuous water-break test is an effective visual method to check the adhesion of organic oil and grease films. You pour distilled water along the inside wall of the glassware; if the water forms a continuous thin film, the surface is perfectly clean. Conversely, we use a phenolphthalein solution added to the final rinse water to check for residual alkalinity from cleaning chemicals.

2.2 Assessing Residual Ions Using Conductivity Measurement

Measuring the conductivity of the final rinse water is a highly quantitative, narrow-band technical solution. This process analyzes the concentration of residual metal ions or mineral salts within the glassware after washing. A precisely calibrated measuring device is needed to compare the conductivity of the rinse water with that of the demineralized input water.

If the conductivity of the rinse water exceeds the specified technical range, that batch of instruments must be returned to the unsuitable processing cycle. Strict control of these physicochemical parameters eliminates interfering components. Therefore, the measurement uncertainty of chemical analyses is always maintained within safe limits.

Measuring the electrical conductivity of the final rinse water is a mandatory requirement to meet the stringent international standard ISO 17025

3. Principles of Ultrasonic Cleaning

3.1 Cavitation Mechanism

Multifrequency ultrasonic cleaning technology possesses significant advantages over manual mechanical techniques. The system operates by transmitting high-frequency sound waves (standard 40 kHz) into the laboratory cleaning liquid. This process continuously creates a narrow-band compression and expansion cycle, forming millions of microscopic air bubbles.
These tiny bubbles move and burst suddenly within microseconds, creating cavitation. This extremely powerful microscopic impulse directly impacts and thoroughly removes stubborn precipitates and chemical residues in the narrow-band hidden corners of analytical instruments. This is the optimal mechanism for deep cleaning burettes, pipettes, or glass volumetric flasks.

3.2 Mechanical Surface Protection of Grade A Glassware

The use of traditional mechanical cleaning brushes always carries the risk of damaging the glass surface structure. The continuous friction of stiff bristles easily causes microscopic scratches inside Grade A glass test tubes. These scratches inadvertently become ideal locations for bacteria and mold to accumulate and reside on the upper layers.
Conversely, ultrasonic cleaning technology is based on indirect fluid flow dynamics. This mechanism completely protects the smoothness of the glass walls, does not cause physical abrasion or blurring of geometric graduations. Therefore, the standard capacity of volumetric measuring instruments always maintains maximum measurement accuracy.

4. As One MUC-63 Large Capacity Ultrasonic Cleaning Tank Solution

4.1 High-Load Solid Stainless Steel Mechanical Structure

To meet the processing capacity of large quantities of tools in industrial workshops, we need to synchronize specialized hardware. Currently, the 63-liter ultrasonic cleaning tank model MUC-63 (Code: 1-1605-02) from As One Japan, distributed by Duc Duong, is the leading solution. The device boasts a chamber structure made from solid stainless steel with superior thickness.
This high-grade stainless steel alloy provides ideal chemical inertness against the effects of strong cleaning chemicals. The device integrates a large-diameter drain valve system capable of handling high pressure loads. This durable mechanical structure allows for quick and safe automatic discharge of dirty solvents.

4.2 Optimizing Heating Performance and Ultrasonic Power

The MUC-63 model’s operating configuration is optimized based on real-world data from the Japanese manufacturer As One. With a large tank capacity of up to 63 liters, the system allows for the simultaneous processing of hundreds of test tubes and beakers in a single cycle. This design helps Production Managers thoroughly address the problem of equipment congestion at the beginning of each shift.
The integrated washing tank features a powerful heating unit (Heater) that helps quickly raise the liquid temperature to the ideal reaction level. The digital control system with LED display allows technicians to precisely program the washing time and temperature. The combination of ultrasonic power and temperature helps to quickly dissolve stubborn grease and oil stains.

ASONE’s ultrasonic cleaning bath helps clean laboratory equipment according to ISO 17025 standards

5. Technical Documentation Method for Monitoring the Cleaning Cycle

5.1 Establishing a Logbook for Auxiliary Equipment Operation

The establishment of documented evidence is a mandatory requirement in ISO IEC 17025 2017 assessments. As required in Section 7.5.1 (Technical Documentation), the laboratory must ensure that the records fully document technical information. The ultrasonic cleaning tank operation logbook must clearly record the time of operation, the type of equipment, and the identification of the personnel responsible.
The standard logbook template must record parameters regarding the concentration of cleaning chemicals and the results of cleanliness verification tests. This narrow-range technical documentation allows for the ability to replicate the operation under conditions as close as possible to the original. The original data obtained must be recorded directly at the time of the analytical operation.

5.2 Record Control and Document Retention

A quality record-keeping system must strictly adhere to information security and safety regulations. Section 8.4.2 clearly stipulates that the laboratory must implement necessary controls for the identification, preservation, and retention of records. Documents demonstrating the consistency of instrument cleaning procedures must be retained long-term.

You need to ensure these technical records are always readily available for quality audit teams. Access to this documented information must be consistent with the plant’s overall confidentiality commitments. Record transparency is key to demonstrating the company’s exemplary management capabilities.

6. Selecting Specialized Cleaning Agents and the Risk of Blurring of Volume Marks

6.1 Classification of Cleaning Chemicals by Stain Type

Testers must absolutely not use ordinary household soaps to clean laboratory equipment. Household chemicals often leave a superfine, electrostatically adhering organic film on the glass surfaces. This superfine film will seriously interfere with digital spectrophotometric measurements.
We need to classify specialized chemicals based on the physicochemical properties of the actual stains. You should apply mild alkaline laboratory solutions to emulsify oils, fats, or biological residues. For metal deposits or inorganic mineral deposits, narrow-band dilute acid solutions (low-concentration HCl) are the optimal choice.

6.2 Preventing the Risk of Blurring of Glass Volume Marks

Although specialized cleaning agents provide high cleaning performance, the risk of mechanical corrosion can still occur. Prolonged immersion of volumetric measuring instruments (pipettes, burettes, volumetric flasks) in an ultrasonic bath containing a strong alkaline solution will cause slight abrasion of the glass. This process will gradually blur the geometric graduations printed on the glass body.

Consequently, the standard capacity of the instrument is altered, directly increasing the measurement uncertainty of the analysis. Therefore, QC technicians must strictly adhere to the contact time and chemical dilution ratio. Good control of kinetic parameters helps protect the integrity and accuracy of the equipment.

Conclusion

In summary, establishing a standardized laboratory instrument cleaning procedure requires close coordination between management policies and technological solutions. You need to prioritize strict adherence to the contamination control regulations of Sections 6.3 and 6.4, utilize the power of micro-mechanical separation from an automated ultrasonic cleaning system, and establish a transparent technical record-keeping system for post-audit purposes. Duc Duong Science and Technology Company is proud to be a provider of comprehensive laboratory solutions and the authorized distributor of the reputable As One ultrasonic cleaning system from Japan in the Vietnamese market.

To receive an optimal price quote for laboratory equipment configuration and a detailed catalog of the As One MUC-63 ultrasonic cleaning system, which meets ISO 17025 standards, please contact our project department directly or fill out the consultation registration form at Contact Duc Duong Company for the fastest assistance from our specialists.

 

DUC DUONG SCIENCE AND TECHNOLOGY COMPANY

Address: 1014/67 Tan Ky Tan Quy, Binh Hung Hoa Ward, Binh Tan District, Ho Chi Minh City

Tel: (028) 3762 8042 – 3762 8043 – 3750 8514 – 3750 8793

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Email: ducduong@ducduongco.com

Website: ducduongco.com

ZALO OA: DUC DUONG SCI

 

FAQ

1. What is the biggest difference between verification and validation in laboratory instrument hygiene?

According to the definition in ISO IEC 17025 2017, verification is the provision of objective evidence that an object meets specified requirements (e.g., the instrument is free of residual alkali after washing, passes the water film test). Meanwhile, validation is the verification of whether those specified requirements are fully satisfied for a specific purpose (e.g., the washing process ensures that the test tube is completely free of DNA, not interfering with molecular biology PCR analysis).

2. Why shouldn’t ordinary household dish soap be used to wash laboratory glassware?

Ordinary dish soaps contain high levels of fragrances and organic foaming agents that are difficult to completely rinse off with ordinary distilled water. They easily leave a superfine, electrostatically adhering organic film on the glass walls of laboratory glassware. This supernatant of organic deposits absorbs light wavelengths and causes serious optical errors when performing chromatographic or digital spectrophotometric measurements in the laboratory.

3. How is the continuous water-break test performed to check for oil and grease stains on glassware?

The continuous water-break test is performed by running a stream of distilled water (or demineralized water type 1) along the inner glass walls of the analytical glassware. If the glass surface is completely free of organic impurities and oil and grease, the water will form a thin, smooth film that continuously and evenly covers the glass walls; conversely, if there are still narrow streaks of oil stains, the water film will immediately break and clump together into small, independent water droplets.

4. What is the recommended frequency for checking the differential pressure and maintaining the mechanical system of the ultrasonic cleaning bath?

To ensure continuous operation of the equipment and stable mechanical separation performance according to ISO 17025 standards, the ultrasonic wave generating electronic circuit and heating unit must be functionally checked at least once a month. The SUS 304 stainless steel tank and the sediment recovery trough below must be flushed and cleaned with 70% alcohol weekly to prevent mold buildup. This prevents the equipment itself from becoming a source of cross-contamination for the next batch of instruments.

5. What mandatory information must be stored in the technical record of glassware cleaning for post-inspection purposes?

According to Clause 7.5.1, the technical record of instrument cleaning must fully record the time and identify the personnel responsible for this auxiliary testing activity. The archived document must clearly include: the batch number of the instrument from the previous analysis, the name of the specialized cleaning chemical, the dilution concentration, the ultrasonic bath cycle temperature, and the results of the cleanliness verification after the rinsing cycle. This document must be kept confidential in accordance with the laboratory’s contractual obligations.