The news in analytical balances comes not from hardware but from user interface and software algorithms that translate electrical signals to weight. “When you put a weight on a balance, the measurement is so much faster than it used to be,” says Ian Csiesniewski, technical director at Mettler Toledo (Columbus, OH). Software upgrades now provide “settling time” on a five-place analytical balance equivalent to times on top-loaders. “And measurement uncertainty—the accuracy level—is getting tighter and tighter. The end-user numbers are a lot more secure.”
Lower measurement uncertainty arises from higher data acquisition speed and the efficiency of the algorithmic evaluation that turns data points into weight data. Key to this conversion is a fast onboard microprocessor.
Mr. Csiesniewski attributes these improvements to development groups that continue to develop products post-launch. “We’re learning more about the hardware capabilities and constantly analyzing performance based on calibration certificates generated during customer service visits.” Provided the balance has computer connectivity, customers can upgrade software via the Internet regardless of instrument age. “They get the benefits of buying a new balance today even though their unit is five or six years old,” Mr. Csiesniewski says.
Improved algorithms provide benefits beyond better, faster weighing results. Since the weigh cells are much more reliable and robust, they maintain performance longer and therefore require less frequent calibration and maintenance.
Calibration and maintenance
Calibration is easy to take for granted or outright ignore, especially in academic labs that lack a business driver for regular, routine calibration. While today’s balances do not require as much calibration and service as older models, users should be aware that operating environment and usage can easily affect both results and calibration frequency. “Modern balances tend to hold calibration longer than previous-generation instruments, but if you’re in a production area, you should not back off on maintenance frequency,” Mr. Csiesniewski tells Lab Manager Magazine. Vibration, noise, heat, cold, and movement, and in some cases frequency of measurement, are signals pointing to more frequent calibration and service.
Frequency and type of calibration vary among industries, and even among companies within markets. Pharmaceutical companies may perform a quick calibration daily; other firms, quarterly or twice yearly. “Remember, though, that simply zeroing a balance is not a calibration,” cautions Markus Jansons, weighing product manager at A&D Weighing (San Jose, CA). “That’s only one point on the line. A true calibration requires several measurement points.”
Calibration can be as simple as procuring NIST (National Institute of Standards and Technology)-traceable weights and performing several measurements. Larger companies often employ outside service organizations that visit periodically to calibrate all of a company’s weighing instruments.
Companies following ISO or industry standards must demonstrate that their balances have been calibrated, but for most firms no official regulatory or industry “guidance” exists stipulating the frequency or type of balance calibration. “It’s up to the company–it depends on how valuable your data is to you,” says Mr. Jansons.
Yet, all in all, today’s balances are quite forgiving. “Five-place balances used to be like racehorses—temperamental and requiring special handling,” says Ian Csiesniewski. “Now they’re racehorses in terms of abilities and workhorses in temperament. Users can be a good deal less respectful to these instruments.”
Communication and data acquisition
“What we’re seeing is a greater need for communication, especially from the balance, as users move away from paper laboratory notebooks into laboratory information management systems (LIMSs) and electronic laboratory notebooks (ELNs),” Markus Jansons observes. “Communications may be wired or wireless, but in every case the goal is to reduce human error.”
For example, quality control or environmental laboratories may run several hundred samples per week; the busiest establishments may encounter such workflows in one day. Copying numbers to three or four decimal places is not only tedious—it may result in skewed results through miscopying weight values or entering them into the wrong location on a spreadsheet. Analysts may not notice anything is wrong until after completing several days’ worth of measurements. The last thing a busy lab wants is rework: having to reweigh samples or, in a worst-case scenario, having to prepare a tray of samples and rerun an experiment.
Most top-line balances include some sort of connectivity option. For example, Rice Lake Weighing Systems (Rice Lake, WI) includes a connection that outputs data directly into Microsoft Excel or Word on a desktop computer. “USB connections are becoming more popular, as many users want data in spreadsheet format,” says Ann Crowley, product manager. Analytical balances are not quite up to HPLC and MS in terms of internal diagnostics: There is no equivalent to messages indicating a leak between the injector and column, for example. But modern balances will indicate if gross excursions occur in terms of instrument readiness.
Analytical balances are no longer considered to be simply weighing instruments that take point measurements. “They have become workflow tools that allow analysts to take care of a process rather than just giving a data point,” Mr. Ciesniewski says. “At one time users had to work very carefully to get great results. Now poor technique is neutralized by instrument capabilities.”