Titrators: Myriad Methods for Quantifying Unknowns

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Those whose only brush with titration came in a freshman chemistry lab may be surprised to learn the significance of titration in companies that manufacture materials, drugs, foods, and beverages.

David Minsk, president of Hanna Instruments (Woonsocket, RI), defines a titrator as “a sophisticated delivery system that performs stoichiometry. It’s a tool that provides better repeatability, accuracy, and efficiency than manual titration.”

There are two major titrator types: potentiometric acid-based designs and Karl Fischer titrators. Those in the first group, which use a pH or redox probe, resemble pH meters in their ability to derive acid strength and total acidity; Karl Fischer titrators measure water content in foods, materials, biofuels, etc.

Most titration work occurs in quality control (QC) laboratories. A survey found that 75 percent of titrators are used in QC, 20 percent in research, and 5 percent in clinical labs. More than half of those surveyed had more than one titrator, with 10 percent owning four or more. Of specific titration modes, more than half fall under the “potentiometric” category, and 21 percent each for volumetric and coulometric Karl Fischer titrations.

All those surveyed considered instrument cost during the purchasing process. This is not unusual when you consider that everyone who performs titration professionally has at one time done it on the cheap with a burette, an Erlenmeyer flask, and either a colorimetric indicator, pH paper, or a pH meter. Dedicated titration systems range in price from about $5,000 to more than $100,000. Yet only 10 percent of those surveyed listed instrument cost as the top reason for choosing one titrator over another.

After price, our readers considered performance, reliability/maintenance, service, support, and ease of use when purchasing a titrator. Experience with a particular vendor or product line was the number-one factor (53 percent) in selecting a specific instrument.

Bucking the trend

Don Vreeland, president of Analyticon Instruments (Springfield, NJ) sums up developments and trends in titration as “flexibility and versatility.” Different industries have different titration needs, Mr. Vreeland explains. “These range from low-cost, easy-to-use, single-type titrations to complex, multi-chemistry, multielectrode, multi-sample, and multireagent analysis.” The point: Select your titrator with current needs in mind, and perhaps with a thought toward expanding future capabilities.

A major trend for lab instruments in general, and titrators in particular, has been to supply each instrument with a computer for data acquisition, logging, and massaging. Not all companies have gone along with this approach. “There is no need to have a computer attached to each instrument in the lab,” Mr. Vreeland says. “Our instruments come with software for downloading and archiving data through an RS-232, a LAN, or USB interface, but the computer is not required to operate the instrument.”

There are good arguments for not computerizing. Barring regulatory requirements, controlling all functions from the instrument itself minimizes cost and footprint, flattens the learning curve, and lowers costs. For those so inclined, complex, multichemistry titrations may be fully automated through standard, off-the-shelf equipment without customized software or programming – that is, provided the titrator possesses some “smarts.” Analyticon’s instruments store up to 80 pre- and user-defined methods that range from simple pH adjustment and pH microtitration to automated calibration, blank determination, and subsequent sample analysis, all from a built-in keypad.

When packaged with methods targeted to specific industries, titrators are a convenient way to consolidate several analyses with one investment. Because wineries are significant purchasers of Hanna Instruments’ titrators, the company has bundled methods for analyzing pH and sulfur, two components that affect a wine’s taste and longevity. “We market these instruments as multi-parameter analyzers for wine,” says Mr. Minsk. Hanna similarly packages methods for food – for example, a leading ketchup manufacturer owns several instruments that it purchased “for test frequency and analyzing two or three core quality parameters.”

Methods are of varying value to customers, says Mr. Minsk. About one-third of customers use their own methods; the remainder rely on vendor-supplied methods and training. The challenge is providing an instrument that cuts through widely disparate skill sets. “You have to reassure customers that the instrument will not intimidate them,” he adds.

Versatility is key

George Porter, titration product manager at Metrohm USA (Riverview, FL), observes that “the days of single titrator analysis are fading fast. Purchasers want to maximize their investment and get as much as possible out of the instrument.” Major vendors have overhauled user interfaces to include touch screens, and even stand-alone titrators can benefit from automation and sample prep tools, particularly in high-throughput settings (e.g., QC for foods or chemicals). Up to 40 percent of surveyed users employed an auto-sampler; leading sample preparation methods were homogenization (27 percent), drying (18 percent), and evaporation (12 percent). “Workloads are not going down, and companies are not adding staff,” Porter adds.

Within the automation categories, sample changers and liquid handlers are the most common features. Some titrators come equipped with pipetting and dosing technology (in addition to the titrator itself), but addons like ovens are usually purchased separately.

Decisions to automate operations like dispensing and sample prep are not made lightly, because this equipment can be expensive. One tends to think of throughput as a crossing point: The more samples run per unit time, the greater the need to automate. A natural expectation from this line of thinking is that automation is always faster. That is not true. Sample prep and automation require some user input and have learning curves of their own, while some technicians are very fast.

The best arguments for automation and for sophisticated data acquisition tools are consistency, data quality, and data integrity. Instruments perform repetitive tasks faithfully and accurately, and they never tire of recording and tracking samples as even the best technician sometimes does.

Automated titrators deliver precise volumes of titrant through “step pumps.” Hanna Instruments offers Karl Fisher titrators with 40,000-step pumps. “That level of accuracy provides fine-tuning and repeatability that is impossible with a human operator,” says Mr. Minsk.

For additional resources on titrators including useful articles and a list of manufacturers, visit www.labmanager.com/titrators.

Categories: Product Focus

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Changing Spaces

Published: December 1, 2011

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Changing Spaces

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