Calibration of commonly used glass measuring instruments

In a chemical analysis laboratory, an error of 1 milliliter may lead to inaccurate experimental results. The JJG196-2019 "Verification Regulations for Commonly Used Glass Measuring Instruments" issued by the State Administration for Market Regulation in 2019 is a technical specification formulated to ensure the measurement accuracy of such precision glass instruments. As the cornerstone of laboratory value traceability, this regulation directly affects the reliability of data in key areas such as food and drug testing and environmental monitoring.

1、 Analysis of the Core Points of the Regulations

JJG196-2019's requirements for capacity tolerance are precise to the microliter level:The allowable deviation of AJI25mL graduated pipette on the 0.05mL graduated line is ± 0.05mL, and the allowable error for Class B is relaxed to ± 0.10mL. This classification management reflects the concept of precision control, for example, in vaccine research and development laboratories, it is necessary to useAJIMeasuring instruments, while conventional water quality testing can use B-grade instruments.

The sealing test adopts negative pressure testing method, requiring the measuring instrument to maintain no leakage for 30 seconds under a negative pressure of 50kPa. A third-party testing agency once neglected this testing step, resulting in the rupture of the volumetric flask during vacuum filtration, causing the loss of precious samples. This case highlights the practical value of sealing testing.

The calibration of the graduation line adopts laser interferometry with a resolution of 0.001mm. The latest experimental data shows that a temperature change of 1 ℃ can cause a volume change of 0.0026% in the glass measuring instrument. Therefore, the regulation strictly stipulates that the calibration environment temperature is 20 ± 0.5 ℃. A certain metrology institute once caused a 1.5 ℃ fluctuation in ambient temperature due to air conditioning failure, resulting in the invalidation of the entire batch of calibration certificates and direct economic losses exceeding 100000 yuan.

2、 Standard Operating Practice

The selection of electronic balance should meet the minimum weighing capacity of ≤ 0.1% of the tested capacity. If calibrating a 100mL volumetric flask, a balance with d=0.1mg should be used. A pharmaceutical company's QC laboratory used a regular electronic balance to calibrate micro pipettes, resulting in measurement uncertainty exceeding the allowable value by three times, ultimately leading to a product recall incident.

The temperature control accuracy of the constant temperature water bath should reach ± 0.1 ℃, and it is recommended to use a two-stage circulating water bath system. Experiments have shown that uneven water temperature can lead to a volume deviation of 0.03% in measuring instruments, which has a particularly significant impact on measuring instruments below 10mL. A certain environmental monitoring station improved the water circulation path and increased the qualification rate from 82% to 98%.

The data processing adopts the rounding value comparison method. For example, during a calibration of a 25mL burette, 24.998mL was obtained, and after rounding to 0.01mL according to the regulations, 25.00mL was obtained, which meets the tolerance requirements. But if the original data is 24.994mL, it will be judged as unqualified after rounding. This data processing method requires verification personnel to strictly master the rules of contract revision.

3、 Analysis of Typical Application Scenarios

In the pharmaceutical industry GMP certification, the calibration record of measuring instruments must include complete information such as environmental temperature and humidity, standard instrument number, correction value, etc. A biopharmaceutical company was issued 483 defects due to the lack of water temperature records, resulting in a delay of 6 months in the launch of the new product. This reminds us that the implementation of regulations must adhere to the principle of 'writing what is done, doing what is written'.

Common issues with third-party testing laboratories include: using expired reference materials, ignoring the temperature equilibrium time of measuring instruments, and incorrectly applying capacity correction factors. Suggest establishing a three-level verification system: operator self inspection, supervisor review, and quality manager spot check, to form a complete quality control loop.

The determination of calibration cycle needs to consider factors such as frequency of use and corrosiveness of the medium. It is recommended to shorten the calibration cycle of the strong acid dielectric analyzer to 3 months, while the pure water dispenser can maintain a cycle of 1 year. A petrochemical company laboratory optimized the calibration cycle of acid burettes from 12 months to 6 months through big data analysis and usage records, resulting in a 40% decrease in equipment failure rate.

With the advancement of analytical techniques, JJG196 regulations will continue to evolve. In 2022, the International Organization for Legal Metrology (OIML) has released a new draft to include digital burettes in its regulatory scope. Laboratory personnel should establish a continuous learning mechanism, pay attention to international standard developments, and regularly participate in CNAS organized value comparison activities. It is recommended to conduct internal blind sample assessments every quarter, use CRM certified standard solutions to verify the accuracy of measuring instruments, and establish a three-dimensional quality assurance system. Only by translating regulatory requirements into daily operational habits can we truly safeguard the scientific and credible nature of experimental data.

Company Background Introduction:

Ze Heng The advantage of Huapu in metrology calibration, verification, and confirmation is that it focuses on providing quality control services for biopharmaceuticals. It is very familiar with some special instruments, and its main team comes from pharmaceutical companies and instrument manufacturers, who are familiar with instrument and GMP regulations. For example, our team has specially developed a fluorescence quantitative PCR instrument calibration device to replace imports, which greatly reduces the cost of fluorescence quantitative/qualitative PCR instrument calibration (far lower than other peers); We have developed an internal calibration protocol for the cell counter; Developed internal calibration procedures for cell recovery instruments; The calibration procedure of gel electrophoresis scanner was developed; We have developed integrated wireless probes for lower and higher temperatures required for temperature verification, reducing the cost of users using probes extensively and replacing imports; There are many more examples, as we all come from a biological background, we pay attention to the process requirements of every biological user, focus on biopharmaceutical instruments and equipment, and strive to "go with quality and do instrument and equipment quality control" in order to make biopharmaceuticals safer.

We work closely with other units in terms of services, including mandatory inspections, special inspections, or services that cannot be done, to help customers send and collect items on their behalf, saving time, effort, and convenience.

Ze Heng Huapu is a professional service provider dedicated to providing laboratory instrument calibration, instrument and equipment validation, and factory validation for the biopharmaceutical industry. We provide pharmaceutical clients with one-stop quality control outsourcing services for QC/QA/engineering/validation/production departments.