Getting More Accurate Results with Analytical Balances
Article Feb 13, 2017 | Written by Kevin Hill, Quality Scale Unlimited
Credit: Kevin Hill
Analytical balances are some of the most common weighing instruments used in lab operations, especially for sample preparation. This is often the most time-consuming activity, and weighing errors at this stage can result in a loss of both time and money. As such, it’s critical to ensure that your analytical balances provide precise results. Here are 6 tips to help you get more accurate results from these instruments:
1. Pick the Right Environment
The accuracy of any weighing equipment can be affected by environmental factors and operating conditions, such as temperature, air pressure, vibrations and humidity. Place your balance on a firm and level surface in an area where exposure to environmental factors is minimal.
Shield the balance and samples from ambient drafts, moisture and temperature fluctuations. Some analytical balances monitor these conditions to determine uncertainty in results, but you should still keep them as constant as possible. If you cannot find a low-traffic area for it, use a weighing table that absorbs vibrations.
2. Perform Regular Scale Calibration
Calibration should be performed regularly, either on-site or by sending the instrument to an accredited calibration lab. Testing your instruments against results from a standard device with known accuracy helps ensure more accurate and traceable results.
In addition, tare the balance before measuring each weight, and record the container’s weight as well. Remember, your balance needs to be level before it can be calibrated. Scale calibration should only be performed by trained and experienced technicians, since it affects the reliability of your data.
3. Minimize Contact with the Balance
Vibrations can affect the performance of analytical balances, so avoid leaning on the weighing table or even touching it during operation. Use draft shields to protect the balance and sample from disturbance during a weighing, since the movement of air can also cause vibrations.
Always use gloves or tongs while handling a sample for weighing, and avoid any contact of your bare hands with the balance. After taring, even your fingerprints can add mass to the weighing container and affect its accuracy, so take every possible precaution.
4. Handle Samples Properly
To make sure that weighing results are accurate, follow the appropriate procedures for handling samples. Samples should be allowed to reach ambient temperature if they are too hot or cold, and weighed in the correct size vessel. For instance, a vessel that’s too small increases the chance of spills. Make sure you use the correct balance for the samples you’re weighing, since some balances cannot weigh very small samples or large ones. Place samples in the center of the balance and close the doors to prevent hygroscopic samples from absorbing moisture.
5. Protect Against Electrostatic Charge
The result displayed by an analytical balance can also be affected by electromagnetic fields between the sample and the balance. This leads to distortions of up to a gram, particularly when you’re working with samples that feature dry non-conductive materials.
To minimize the effect of electrostatic charge while weighing in increments of milligrams or smaller, place a discharge ionizer next to the balance. Similar errors can also occur due to fluctuations in power supply, so check if that may be causing a problem and move the balance to a stable power supply if it is.
6. Clean and Maintain Balances
It’s important to keep weighing instruments clean and well-maintained. Before you use the balance, remove any dust, debris and particles from the cabinet and weighing pan with a soft brush and an appropriate solvent. Also, let it warm up first if you unplugged it while cleaning.
Create proper equipment maintenance and cleaning schedule, both for daily operations and long-term upkeep. This helps to keep your analytical balances free from contamination, prevents weighing errors and ensures accurate results. As with any other precision instrument, proper care can make all the difference!
Kevin Hill heads up the marketing and provides technical expertise to the sales and service teams at Quality Scales Unlimited in Byron, California.