Features and future performance should be considered while wandering through the wide range of options
For everyday labs, analytical balances are the most accurate. These instruments can usually measure weights to 0.1 milligrams or better in accuracy. In describing analytical balances, Fernando Calderon, account manager at Ohaus (Parsippany, NJ), says, “They are used in many labs, ranging from pharmaceutical compounding and quality-control monitoring to flavor development in food technology.”
In addition, analytical balances are used in many procedures. “Generally, users will elect to use an analytical balance for small samples—generally a few grams or less—that need to be weighed precisely,” says Ian Ciesniewski, technical director at Mettler Toledo (Columbus, OH). “Typical samples would be less than 100 milligrams.” Some of the most common uses of these balances include preparing standards or buffer recipes and weighing peptides.
This instrument category contains many options, and scientists should be sure to consider a variety of features.
Desirable features
When asked about the top features to consider in buying an analytical balance, Calderon points out capacity, readability, application, and price.
Ciesniewski adds, “Ensure that the precision and accuracy are at least sufficient to meet process tolerance and requirements.” In addition, he points out that: “Users should firm up their requirements and select balances that meet their requirements. The budget for the balance should fit the specifications required, rather than trying to struggle with an inappropriate balance that just happened to fit an arbitrary budget figure. In other words: Research the market.”
Some other features also make an analytical balance easier to use. “When selecting a balance, consider the benefits offered by built-in value features, such as auto doors and other productivity and efficiency tools, which will allow adherence to standard operating procedures, ease of use, and ease of cleaning,” Ciesniewski says.
Today’s analytical balances also offer some automated advances, such as adjustment technologies. These can “ensure that environmental drift is negated at all times,” Ciesniewski notes. “Contrary to what some users may falsely believe, this feature does not interfere with the metrological testing of the instrument or interfere with any regulated procedures.” Instead, auto-adjustment makes a balance drift-free, which “avoids erroneous test data due to changing conditions in the lab,” Ciesniewski indicates.
With the right balance, scientists can make it work better for longer. A key factor is keeping a balance clean. So, buy one that makes that easy. “Clean balances need less maintenance, and will not suffer deterioration in performance that may be due to a buildup of powder inside the weigh-cell housing,” Ciesniewski says. “Removable doors, weigh pan, weigh-chamber base plate, and front glass allow rapid cleaning of a balance at any time.”
Maintaining performance
To get the best results, an analytical balance takes some care. “Make sure the balance is always level, away from doors, windows, and drafts in a room with adequate temperature control,” Calderon encourages. Even daily procedures make a difference. “Perform a calibration check daily, and readjust as necessary,” Calderon advises, and “never severely overload your balance.”
Mettler Toledo’s Excellence Plus XPE Analytical Balances provide a range of weighing capabilities. (Image courtesy of Mettler Toledo.)
One of the easiest things to do that improves performance, Calderon notes, is “to keep the balance is the same place as much as possible.”
Some of the ongoing maintenance, though, requires a professional. “It is essential that analytical balances receive preventative maintenance, performed by a correctly certified, manufacturer-trained technician,” Ciesniewski explains. “If your service provider cannot prove—by way of a training certificate from the manufacturer—that they are certified to service the given balance, then the performance of your balance will deteriorate with time.”
As Ciesniewski concludes, “Manufacturer-authorized preventative maintenance, coupled with appropriate placement and usage, should give you ‘as-new’ performance for many, many years.”
Market sampling
Although the many analytical balances available make a complete survey far beyond the scope of this article, it’s worth considering a few of them.
Mettler Toledo’s Excellence Plus XPE Analytical Balances provide a minimum display of 0.01, 0.1, or 1 milligram and total capacities of 120, 220, or 520 grams. These instruments are adjusted with proFACT, which provides fully automatic time and/or temperature controlled internal adjustment.
With similar features, scientists can also consider Mettler Toledo’s Excellence XSE Analytical Balances, the MS-TS Analytical Balance, and others. The Ohaus Adventurer AX Analytical Balances also deliver automatic internal and external calibration. The total capacities come in 120- or 320-gram versions, and the minimum display is 0.1 milligram.
The Ohaus Explorer Semi-Micro provides 0.01-milligram readability and capacities of as much as 200 grams. The company adds that “the AutoCal Internal Adjustment system ensures accuracy of results in applications that require high precision.” In addition, it comes with an intuitive, icon-driven user interface and responsive touchscreen display.
Like many other vendors, Ohaus offers a diverse line of analytical balances that also includes the Explorer Analytical, Adventurer Analytical, and Pioneer Plus Analytical. Although the Pioneer Plus Analytical is advertised as economical, it still includes advanced options, and the company notes that “three filter modes and adjustable zero tracking help to adjust the balance’s sensitivity to environmental disturbances, vibrations, and slow-filling applications.”
In Göttingen, Germany, Sartorius offers analytical balances that weigh as much as 520 grams, at down to 0.01-milligram resolution. For example, its Cubis Analytical Balance comes in 60-, 120-, and 220-gram weight capacities with readabilities of 0.01-, 0.02-, and 0.05-milligram readability.
From A&D Weighing (San Jose, CA), scientists can also explore a range of analytical balances. These include the Galaxy HR Series Balances, which come in eight models. The company describes these balances as having simple user navigation, which makes any one of these an “ideal entry-level balance from lab to industrial weighing environments.”
To shop in this market, it helps to find a source of consolidated information, and Cole-Parmer (Vernon Hills, IL) provides a substantial list at: www.coleparmer.com/c/analytical-balances. Beyond some of the balances already mentioned, Cole-Parmer provides information on the Cole-Parmer Symmetry, which is a family of balances with capacities from 120 to 220 grams, and readability of 0.1 milligram. In addition, the company points out the “digital filters compensate for vibration, drafts, or temperature changes.”
When it comes to weighing quantities down to low levels of accuracy, every lab needs an analytical balance. As this article reveals, many features must be considered, and a wide variety of vendors offer complete families of instruments. It’s worth exploring a few options and investigating the experiences that other scientists found with particular instruments and suppliers. Only then can the best instrument be found for a specific lab.
Mike May is a freelance writer and editor living in Texas. He can be reached at [email protected]