pH Meters: Measuring Acids and Bases with New Accuracy and Reliability

An old analog pH meter seemed accurate enough, as long as the task didn’t require much accuracy. Today’s meters must be more accurate and provide more reproducible results. In some cases, pH meters do even more.

Christine Brink, market manager for electrochemistry at Mettler- Toledo (Columbus, OH), points out that some customers want multifunction meters. A device might measure various parameters, including pH, conductivity, ion concentration, and oxidation reduction potential.

Beyond accuracy and flexibility in today’s pH meters, some features make measurements much easier to obtain. For example, yesterday’s clunky electrode stands gave way to multi-segmented arms that more easily position the electrode in the sample.

Modifying the meter

“We subscribe to the pH meter that is not just a pH meter,” says David Minsk, president of Hanna Instruments (Smithfield, RI). “We try to understand the nuances of the wide range of applications where pH meters are used and then optimize them for those applications.”

For example, Hanna Instruments offers pH meters for use in the food and beverage industry. This includes the development of specific electrodes for food. “Most standard lab-grade electrodes cannot penetrate semisolid samples like food,” says Minsk. So Hanna Instruments developed pH electrodes that go in samples such as cheese and sauces, all without diluting the sample. “We also use nontoxic materials for these electrodes so they do not tarnish the sample.”

Today’s pH meters also incorporate improved ergonomics in various forms.

“For a portable pH meter,” says Brink, “that means being easier to hold and use.” She adds, “Today’s benchtop systems include easier menus and simpler ways to make corrections or change methods.”

Measuring a meter’s life

“A pH meter should last a couple years at a bare minimum,” says Minsk. “The consumable is the electrode.” The life span of a pH meter electrode depends on the samples being tested. “With a high-temperature sample, the electrode will last only three to six months,” Minsk says. “For clear water at ambient temperature, the electrode could last twelve to eighteen months if properly maintained by the customer.”

For the meter itself, new features drive some replacements. For example, any company working on drug development and production will want a meter that offers good laboratory practices (GLP). GLP allow the user to record the meter’s last calibration date and time. This is especially beneficial when the meter is used by various users who are required to maintain a specified accuracy standard. “Meters that record and store data in an Excel file are also becoming more prominent,” says Minsk, “and that might prompt someone to upgrade.”

Brink adds that someone might upgrade a pH meter to obtain added security features. “Incompatibility between the sample and electrodes could also lead to replacement,” she says. “The right electrodes can make all the difference in accuracy and reproducibility.”

At the University of North Carolina, Pembroke, chemistry laboratory teaching assistant Shanna May Harrelson likes a pH meter to provide “ease of use for students and ease of maintenance when needed.” She’d also like to see pH meters that provide “stepby- step directions for calibration for students” and “trouble-shooting directions when needed.”

When buying a new pH meter, make sure to consider the meter’s features as well as the available electrodes. It’s the entire platform that determines the range of applications and overall fit with your needs.

Article Courtesy of Lab Manager Magazine: pH Meters: Measuring Acids and Bases with New Accuracy and Reliability

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