Weighing is one of the most common tasks in the laboratory. Reliable analytical results begin with accurate weighing. And while modern balances are sophisticated enough to not require a specifically designed weighing room any longer, they are still extremely sensitive instruments beholden to their environment, use and care.
For example, vibration, drafts/airflow, heat/temperature and humidity can all lead to invalid weighing results. Ideally, balances should be located in a laboratory on the ground floor of the building, as this is typically the location with the least vibrations. The less doors and windows in the room, the better. Direct sunlight should be avoided, and relative humidity should be maintained between 45% and 60%.
While balance location plays a role in accuracy and reproducibility, there is another critical component: calibration.
Compliance features
Calibration is the basis for ensuring measurements are accurate within specified limits. Calibration also ensures that weighing equipment satisfies industrial standards, which is good practice whether you are in a regulated environment or not. Using non-calibrated equipment can lead to production problems such as unscheduled downtime, inferior product quality, process and audit issues, product rework and recalls. Experts suggest once a year calibration as a starting point, but each lab and situation is different.
Beyond the various standards that relate to calibration intervals, a risk-based methodology is often appropriate. If a measurement is considered low-risk then preventative maintenance, routine testing and calibration can be carried out less frequently. On the other hand, weighing devices performing high-risk measurements will require these methods more frequently.
In highly regulated industries like pharmaceutical and food & beverage, compliance is of the utmost importance. Compliance with regulations ensures good science, accurate results and safe manufacturing. While crucial, compliance doesn’t need to be complicated. To ensure simplicity, manufacturers have integrated software and smart features directly into analytical balances to help users fulfill regulation and data integrity requirements. Some examples include:
SOP Workflow
Some laboratory software allows you to program standard operating procedures (SOPs) into the balance workflow. Then, the software guides users step-by-step at the instrument terminal to prevent errors. This is an ideal way to ensure repeatability as there should be no variance in procedure between users. Lab personnel can also design and integrate weighing methods for specific samples. In these cases, on-screen instructions and guidance are intuitive, reducing time-consuming user training.
Traceability and Data Integrity
A user management feature controls which users are authorized to run which tests, minimizing non-compliance and costly rework. Having secure, user profiles allows all activity and data to be traced to an individual, meaning a comprehensive audit trail is always available. By logging all data, including metadata, along the entire workflow, manufacturers can ensure complete traceability and data integrity according to the ALCOA+ framework.
Audit-ready
A central user management feature is just one way to ensure your lab is audit-ready. Other attributes, like a detailed audit trail and electronic signatures, support compliance with regulations such as 21 CFR Part 11. For audits, software that supports access to data 24/7, from anywhere, is crucial—lab managers and QA/QC personnel dealing with an audit need to ensure data is both quickly and easily accessible. The ability to create customized reports is also helpful when audits are underway.
Service and Non-compliance Reminders
Part of an audit is ensuring balances in a laboratory are accurately calibrated, and have not been used for analysis during a time of recalibration. Balances need to be calibrated when they are first installed and at designated time intervals thereafter. Lab managers and OA/QC professionals track the maintenance and recalibration schedules for all lab instrumentation, so it’s not hard for one to slip through the cracks. A quality software system should notify you when a balance test or service is due, ensuring all instruments are kept up to date and weighing results are valid.
Cleaning and maintenance
As with any electronic, cleaning and regular maintenance can help ensure a longer life. A good rule of thumb is to clean the balance after every use, or whenever the weighing substance is changed. Working with hazardous materials might call for even tighter rules.
Cleaning a balance is relatively simple. Follow these 7 steps:
- Protect yourself and have the SOP ready
- Switch off the balance
- Clean area around the balance
- Disassemble removable parts
- Clean the balance itself
- Use a lint-free cloth moistened with a mild cleaning agent to clean and remove any spilt material on the surface of the balance. First remove powder and dust, then sticky substances.
- Clean removable parts
- Use a damp cloth or tissue and clean with a mild cleaning agent containing ethanol or simply place them in the dishwasher.
- Reassemble balance and switch on
To protect the balance from dirt and hazardous or sticky substances, use replaceable protective covers. For safe dosing and to avoid accidental spills, use specially designed weighing funnels. When the balance is not in use, use a dust cover to keep it safe.
Regular maintenance for a balance is good. But regular cleaning and preventative maintenance is even better. Preventative maintenance, in combination with a good calibration schedule, ensures the balance will continue to operate to specification, while also minimizing the risk of unexpected failures. Specifically, external and internal cleaning prohibits dust and debris from entering the weighing cell and contaminating the electronics. When electronics, sensors, and faultless keyboard/display functions are checked, it helps to ensure the balance is operating according to manufacturer specifications. Additionally, preventative maintenance reduces costs associated with emergency repairs, and allows maintenance costs to be budgeted predictably, particularly if a contract includes an extended warranty clause.