Analytical Balances

Sartorius analytical balances are sensitive lab instruments with a readability of 0.1 mg and a maximum capacity between 60 g and 520 g designed to accurately measure mass. Due to their high sensitivity the weighing process with analytical balances is prone to be affected by air drafts and thus the instruments are equipped with a draft shield.

“Analytical balances” or “balances for analytical purposes” as defined in Pharmacopoeias the term analytical balance is often expanded to semi-micro balances with readability of 0.01 mg and a maximum capacity up to 220 g. Also these balances are equipped with a draft shield to protect the instrument against air currents.

It is critical that you monitor and calibrate your analytical balance regularly. You can use automatic internal calibration (isoCAL) but additionally to this, it is recommended to calibrate the balance with external certified weights as well. The frequency of external calibration depends on numerous factors, e.g.  

• Frequency of usage: calibration should be done more often if the balance is used daily, as compared to the scales which are used on a weekly basis. If you use the balances daily, they should be calibrated at least once a day.  
• Changing environmental conditions: if a balance is kept in changing environmental conditions or the scales are located in a place close to vibration source, AC system, in front of window, next to a door etc. we recommend to calibrate the balance more often. 
• Importance of the accuracy of the weighing results: 
• Manufacturer´s recommendation 
• Relocation: your balance or scale must be calibrated after relocation. Why? Gravity is not the same everywhere on Earth, therefore every place in the world is positioned differently to “magnetic north” This results in slight gravitational differences, depending on a particular location’s altitude compared to sea level. As balances measure the force of gravity pulling the mass toward the center of the Earth, as soon as you relocate your balance (e.g. even to a different floor), the balance will display a different value, as the force will vary. 

Analytical balances combine high measuring accuracy with a short measuring time of only a few seconds. They are predestined for routine use in a wide range of applications in many laboratories. They are used for example in back weighing procedures,  totalizing, averaging, and dosing applications or generally in sample preparation for subsequent analytics.  

An analytical balance comes with a readability of 0.1 mg, whereas a precision balance typically has readability of ≥1 mg. So an analytical balance has at least a 10-times higher readability compared to a precision balance.  

Just determine the number of digits specified for your weighing instrument’s resolution, then check the graph below for the particular accuracy class that your weight must have. The nominal mass value of your weight should be more than 80% of the maximum capacity of your weighing instrument. 

Example: Suppose your weighing instrument has a maximum capacity of 2,200 g and a readability of 0.01 g. This yields 220,000 digits, which correspond to a class E2 weight. Select 2,000 g as the nominal mass value. 

Put the balance in stand-by mode, perform the necessary cleaning steps, careful not to leave residue on the pan. Complete the step with calibration of the balance and perform the daily check. 

Most importantly are the balance qualification, regular calibration and monitoring of the minimum sample weight. In addition to these basic requirements dedicated workflows for selected monographs (e.g. uniformity of dosage testing, loss on drying and residue on ignition) are of interest.

Concerning electronic records and signatures FDA guideline 21 CFR part 11 defines requirements on data integrity and traceability. The Cubis^® II MCA balance, with pharma package, offers technical controls to follow 21 CFR part 11 and Pharma GMP ALCOA principles (accurate, legible, contemporaneous, original, and attributable).

To properly use an analytical balance, it is crucial to exercise great care and ensure that the environment is free from disturbances. Analytical balances are highly sensitive to even the slightest changes in atmosphere and foot traffic, so it is essential to use them in a room with minimal movement, temperature fluctuations, and draft. Employing anti-vibration tables can further help in achieving accurate results.

When using an Analytical Balance, it is important to verify that it meets industry standards (FDA, GMP, Pharmacopoeias), perform necessary calibrations, and allow the balance to reach its operating temperature before use. During the weighing process, place the substance on a pre-weighed and tared weighing paper or container. To avoid adding mass through fingerprints, always use gloves, tweezers, or tongs.

After using the balance, it is important to clean the instrument gently to remove any sample residues that may have contaminated the balance. This ensures the accuracy and longevity of the analytical balance for future use.

Typically, the recommended external test weight and it’s accuracy class can be found in the instrument’s user manual and the datasheet. The nominal mass of your test weight should be more than 80% of the maximum capacity of your weighing instrument. Using multiple test loads the nominal mass of the weights should cover a broad spectrum of the instrument’s weighing range.

For the calibration of analytical balances typically test weights class E2 with a nominal mass value between 100 g and 500 g are recommended.

The answer is dependent on the balance and display type. Cubis^® MCA balances offer a software application with guided workflow for routine and deep cleaning and a help function with useful information how to clean different components. The user simply follows the instructions and in deep cleaning mode the instrument executes some checks at the end to ensure the instrument is properly reassembled.

For other balance lines set the instrument to stand-by mode, perform the necessary cleaning steps, careful not to leave residue on the pan. Complete the step with calibration of the balance and perform the daily check. For information on suitable cleaning agents refer to the balance user manual.