Laboratory Balances Need Special Care -- Does Your Lab Weigh Up?
Does your lab have a best practice policy for the use of balances? Do all the personnel know how to care for and maintain them in perfect condition? Weighing is likely to be the most common task performed in your laboratory and plays an important role in its overall efficiency. Technological advances have ensured that today's laboratory balances operate with much greater precision than their predecessors and are much simpler to use. Weighing times have been reduced and the balances are more adaptable.
However, absolute care is necessary to maintain their accuracy and reduce the opportunity for errors. It doesn't take very much to throw off the sensitive equipment. This guide provides a practical overview for the proper care of laboratory balances, and important information for all lab staff when handling them.
The External Environment
There are numerous external factors arising from the environment that influence the precise operation of an analytical balance. The major concerns are:
Maintaining Uniform Temperature
The balance is designed for operating in a normal range of temperatures. However, once acclimatised to the lab's atmosphere, any sudden variation in temperature can cause problems and produce unwanted variances.
Avoid these potential risks when positioning balances:
- drafts from windows, air conditioner vents and doors that constantly open and close
- exposure to direct sunlight
Ideally, balances should be positioned on a concrete floored laboratory. However, this is not always possible and a weighing table located on a solid countertop will absorb vibrations adequately. Additionally, balances should be placed well away from heavy traffic areas as these are likely to produce unwanted movement.
Preventing Electrostatic Charge
Often dry samples and containers will acquire an electrostatic charge which causes weighing errors. Some more sophisticated balances can detect this automatically, but placing an anti-static device or discharge ioniser next to a balance will prevent the issue.
Other external factors concerning the setup for overall efficiency and safety in the laboratory should not be overlooked when locating balances. Allocating specific spaces and separating wet and dry areas is paramount.
The Causes for Internal Error
A number of errors can occur because of a lapse in operating procedures when weighing and handling samples. Common problems occur when sample weights do not stabilise and gradually increase or decrease.
Proper Handling of Warm and Absorbent Materials
- Weigh hygroscopic samples rapidly and ensure they are well protected as they will quickly absorb moisture.
- Allow warm substances, particularly those from drying ovens, to cool in dry environments, preferably in the lab's desiccator, to prevent any moisture absorption before weighing.
Handling the Balance
Naturally operators understand that careful handling is mandatory for correct weighing, but unfortunately small slip-ups happen from time to time when lab personnel are not totally alert. Common inaccuracies occur when they are not careful when performing simple tasks such as:
- Closing the door of the balance properly to completely isolate the sample from the lab environment
- Taking care not to leaving fingerprint oils on samples or containers
- Avoiding breathing heavily on samples
Proper Maintenance Procedures
It is essential to initiate a calibration schedule for all lab balances. Some models will have an internal self-calibration function, but many require a manual calibration. This is where the services of a professional calibration company are an excellent option. They can also carry out checks to keep your valuable investments in top working order.
Of course, a strict cleaning regime needs to be maintained in the lb, but precise care is needed for balances. Be particularly mindful of any spills in the weighing area. If extensive cleaning is necessary, take care to:
- Unplug the balance and gently use a moist cloth and mild soap solution. Do not allow the slightest moisture to enter the weighing apparatus.
- Use a soft cloth to dry thoroughly and close the balance door securely.
Because the balance has been unplugged be mindful that it will take a few hours to warm up and come to correct weighing temperature.
Following these procedures in your lab will increase its efficiency, reduce the incidence of weighing errors, and keep your sensitive equipment in top working order.