How To Get the Most Out of Your Analytical Balance

AMERICAN CHEMICAL SOCIETY BROUGHT TO YOU BY The analytical balance is one of the most fundamental and ubiquitous pieces of laboratory equipment in the world. Across all industries, from pharmaceuticals to catalysts, analytical balances help precisely measure the mass of samples to ensure accuracy in chemical formulations. Naturally, the analytical balance market is saturated with options, each varying with respect to specifications, including sensitivity, readability, maximum capacity, accuracy, and weighing speed. Research predicts that the laboratory balances and scales market will reach $1.3 billion by 2028.1 Among this vast sea of product offerings, laboratory managers can find it challenging to know which balances best suit their specific needs. Selecting the right balance is only half the battle, however. Even the best balances are subject to external factors that can significantly affect measurements. Getting the highest-quality results from your analytical balance requires a deep understanding of the influencing factors that can impact its performance. The factors outlined below can affect a balance’s performance, along with guidance on how Sartorius’s Cubis® II series of balances ensures optimal results for users. INFLUENCING FACTORS ON BALANCE PERFORMANCE The most important specifications worth considering when selecting an analytical balance are accuracy, weighing speed, and minimal sample weight. • Accuracy in analytical balances refers to the closeness of the measured value to the true value of the sample. High accuracy is crucial for ensuring that measurements are reliable enough to maintain the integrity of experimental results and product formulations. HOW TO GET THE MOST OUT OF YOUR ANALYTICAL BALANCE AMERICAN CHEMICAL SOCIETY 2 HOW TO GET THE MOST OUT OF YOUR ANALYTICAL BALANCE • Weighing speed, or stabilization time, is the time it takes for an analytical balance to provide a final reading. Faster weighing speeds enhance efficiency in laboratory and production settings by reducing the time required for each measurement, thereby increasing overall throughput. • Minimum sample weight is the smallest amount of a sample that the balance can accurately measure without compromising accuracy.2 This specification helps prevent the acquisition of weight values with high statistical error. Because of the relative measurement uncertainty, the minimum sample weight defines the threshold value between the unsafe operating range (below) and the safe operating range (above). Though analytical balances may come with predefined values for these specifications, a myriad of factors—including electrostatic charge, temperature and pressure changes, and contaminants—can lower the precision of the measured results.3 ELECTROSTATIC CHARGES Electrostatic discharge (ESD) significantly impacts the performance and accuracy of analytical balances.4 Static charges on glassware and samples can lead to substantial measurement errors. These charges interact with the weighing compartment, causing the displayed weight value to drift and fail to stabilize. This instability makes it impossible to acquire a reliable and accurate measurement. ESD problems are particularly pronounced in low- humidity environments, where static buildup is more likely. A number of factors can affect balance precision and accuracy. Credit: Sartorius AMERICAN CHEMICAL SOCIETY 3 HOW TO GET THE MOST OUT OF YOUR ANALYTICAL BALANCE Addressing ESD issues involves implementing measures that include using antistatic devices, grounding the balance, and ensuring proper handling of glassware and samples to mitigate static charge accumulation. Without these precautions, the precision and reliability of analytical balances can be compromised, which leads to inaccurate results that can impact quality control and experimental outcomes. Sartorius’s Cubis II balances mitigate the ESD through a built-in ionizer system. This system features ionizing nozzles that neutralize electrostatic charges on samples and containers as soon as the balance’s draft shield is opened. Additionally, a conductive coating on the glass parts of the balance prevents external electrostatic fields from affecting measurements. These features ensure full discharge of any electrostatic charges to provide stable and accurate readings. By addressing ESD issues, Cubis II balances enhance precision and reliability, reduce measurement drift, and improve overall laboratory efficiency. TEMPERATURE CHANGES Temperature fluctuations can also influence the accuracy and performance of analytical balances.5 In uncontrolled environments, even minor temperature fluctuations—such as sunlight exposure or heating, ventilation, and air-conditioning activity—can cause measurement instability. Such a rapid shift in temperature can lead to fluctuating weight values, which prevent the balance from stabilizing and result in inaccurate readings. Even in controlled laboratory settings, cold-air drafts can disrupt the balance’s operation. When cold air blows across the sample or balance, it induces instability and causes the displayed weight value to drift. This drift occurs because the balance struggles to reach equilibrium, leading to prolonged measurement times and unreliable data. Ensuring a stable-temperature environment is necessary for maintaining the accuracy and reliability of analytical balances, as even small changes can profoundly affect their performance. Cubis II balances automatically compensate for temperature changes to ensure optimal measurement accuracy. One integrated solution is the incorporation of advanced draft-shield technologies that prevent cold air from entering the balance’s inner workings and impacting measurements. Additionally, Cubis II balances feature an internal compensation method that uses a known mass for internal adjustment. This adjustment is automatically triggered by temperature changes or time intervals, with any deviations recorded and compensated. Cubis II balances also offer an external procedure, allowing users to calibrate the balance using calibration weights with traceable mass. AMERICAN CHEMICAL SOCIETY 4 HOW TO GET THE MOST OUT OF YOUR ANALYTICAL BALANCE PRESSURE CHANGES Pressure changes caused by events like weather fluctuations or storms can lead to changes in air buoyancy, which in turn alters the perceived weight of samples.6 As air pressure decreases, so does the buoyant force on the sample, causing the displayed value to be lower than its true weight. Conversely, increasing air pressure increases the buoyant force, making the sample’s weight appear higher. Pressure changes can introduce measurement drift over time. Cubis II balances mitigate the impacts of pressure changes through an advanced internal compensation system. This system, known as IsoCal calibration, continuously monitors the ambient temperature. When it detects significant changes, the balance automatically performs internal adjustments using a known mass. This automatic adjustment process ensures that any deviations caused by pressure fluctuations are accurately compensated. CONTAMINANTS AND THE IMPACT OF BALANCE CLEANING Balances are designed to measure minuscule amounts of substances with high precision, which means they are especially susceptible to contamination from liquids and powder spills.7 Powders, especially those prone to ESD, can adhere to surfaces and affect weighing accuracy. When users are working with small sample weights, even a seemingly trivial spill can significantly impact results and lead to inaccurate data and cross contamination. Any residue left on the weighing pan can similarly affect subsequent measurements, compromising the integrity of future experiments. This makes proper cleaning of analytical balances essential to maintaining their accuracy and reliability.8 Regular and thorough cleaning prevents unreliable results and help ensure personal safety by eliminating hazardous residues. It also prevents sample cross contamination—crucial in environments where purity and precision are needed. Despite the importance of cleanliness, many users may neglect to clean their balances correctly. Several barriers can contribute to this negligence. First, some users do not know proper cleaning procedures. For example, they might not be certain which parts of the balance should or can be cleaned. Further, familiarizing oneself with acceptable cleaning solutions can be daunting. Second, users might be generally reluctant to perform a task they perceive as invasive or complicated. Because laboratory balances can cost thousands of dollars, users might hesitate to risk harming them to do something as seemingly trivial as cleaning. AMERICAN CHEMICAL SOCIETY 5 HOW TO GET THE MOST OUT OF YOUR ANALYTICAL BALANCE Sartorius designed the Cubis II to address the challenges of cleaning analytical balances, keeping user convenience and equipment accuracy in mind. All major parts of the Cubis II susceptible to contamination are easily removable and cleanable, as well as resistant to chemicals. This design allows users to maintain a pristine balance without fear of damaging their device. Beyond this, the Cubis II balances offer an integrated software application that provides users with a guided cleaning workflow. This application offers visual, step-by-step instructions on how to clean the balance, specifying which chemicals to use and details for the entire process. The goal is to simplify the cleaning routine, thus making it accessible and straightforward for users at all experience levels. The balance’s built-in cleaning utility program includes two modes: routine cleaning and deep cleaning. The administrator can set parameters such as cleaning frequency and confirm by electronic signature when the balance was last cleaned. This traceability is a significant benefit for lab managers, who need to ensure that cleaning protocols are followed consistently. By incorporating these novel solutions, Sartorius has made maintaining the Cubis II balance easier and more effective, ultimately enhancing the accuracy and reliability of laboratory measurements. Cleaning the Cubis II balance is easy with its user-friendly, chemical-resistant parts and step-by-step cleaning guidance. Credit: Sartorius © C&EN BRANDLAB AMERICAN CHEMICAL SOCIETY 1155 Sixteenth Street, NW, Washington, DC 20036 6 CONCLUSION The analytical balance is one of the most important tools in any laboratory. But even the best balances can fall short if proper maintenance isn’t done and precautions are not taken. We built the Cubis II analytical balances to automatically mitigate the impact of external variables, such as ESD and temperature and pressure differentials. We’ve also designed our balances to be intuitive and simple to clean, helping users of all experience levels gather accurate measurements. With Sartorius’s Cubis II analytical balances, users can rest assured that their measurements are always the fastest, most accurate, and most reliable possible. REFERENCES 1. KBV Research, Global Laboratory Balances and Scales Market Size, Share & Industry Trends Analysis Report By Product Type (Analytical Balances, Precision Balances, Moisture Balances, Compact Scale, Micro Balance, and Others), By End User, By Regional Outlook and Forecast, 2022–2028, January 2023, https://www.kbvresearch.com/laboratory-balances-and-scales-market/. 2. Julian Haller et. al., Minimum Sample Weights According to USP <41>, OIML R 76 and EURAMET cg-18, Sartorius white paper, August 2020, https://www.sartorius.com/resource/ blob/580758/6e89cff42ec6efa2863140b467dc5463/minimum-weightwhite-paper-en-sartorius-pdf-data.pdf. 3. National Institute of Standards and Technology, “Good Measurement Practice for Understanding Factors Affecting Weighing Operations,” n.d., https://www.nist.gov/document/gmp-10-weighing-operation-factors20190506docx. 4. Sartorius, “Effects of Static Electricity on Analytical Weighing,” application article, March 30, 2020, https://www.sartorius.hr/media/z4nmekh4/staticelectricity-application-article-en-l-sartorius.pdf. 5. J. J. Manley, “On the Observed Variations in the Temperature Coefficients of a Precision Balance,” Proc. R. Soc. A, 86, no. 591 (July 20, 1912): 591–600, https://doi.org/10.1098/RSPA.1912.0051. 6. Karl G. Kehl et. al., “The Influence of Variations in Atmospheric Pressure on the Uncertainty Budget of Weighing Results,” Analyst 125, no. 5 (2000): 959–62. https://doi.org/10.1039/B000346H. 7. Samuel B. Adeloju and A. Bond, “Influence of Laboratory Environment on the Precision and Accuracy of Trace Element Analysis,” Anal.Chem., 57 no. 8 (July 1, 1985): 1728–33, https://doi.org/10.1021/AC00285A050. 8. Lane C. Sander, “Use of Analytical Balances,” J. Res. Natl. Inst. Stand. Technol., 122, (Jan. 12, 2017): 10, https://doi.org/10.6028/jres.122.010.