Tunable diode-laser absorption spectroscopy allows real-time monitoring of water solvent drying

March 21, 2016
TDLAS using Ametek analyzer saves time and cost for pharmaceutical manufacturers.

Engineers at Ametek Process Instruments (Pittsburgh, PA) have shown that tunable diode-laser absorption spectroscopy (TDLAS) can provide the advantages of continuous process control of pharmaceutical drying to manufacturers using water as their primary solvent.

Pharmaceutical quality control requires that the drying process be stopped periodically and samples removed for loss on drying (LOD) analysis. If the product is not dry, the process is restarted and allowed to run for an indeterminate period. This time-consuming process is repeated until the LOD achieves a predetermined value.

However, the growing number of pharmaceutical makers who have moved to aqueous-based processing can now use TDLAS technology as a lower-cost, time-saving procedure to determine dryer end-point, says Ametek. The continuous real-time monitoring can pinpoint the exact moment when a product has dried as much as possible. This determination is then confirmed by LOD analysis, eliminating numerous stops and re-starts of the drying process.

TDLAS effective in water solvent drying

Working with a pharmaceutical manufacturer, Ametek Process Instruments set up a production trial using Ametek's Model 5100 HD analyzer to monitor the batch production of a widely prescribed medication whose synthesis involves the use of water as the final rinse agent.

The trial showed that TDLAS techniques could be used to continuously monitor and control the solvent drying process online, in real time, without operator intervention or process interruption. The results also indicated that TDLAS has the potential to significantly reduce drying times, while improving both production and product quality for pharmaceutical manufacturers and other bulk powder producers who rely on water as the principal solvent in their processes.

Because TDLAS is a noncontact technique, it offers fast response speeds, which can mean substantial savings in both time and cost.

The Model 5100 analyzer has single- and dual-laser platforms with one or two sample cells for measuring different process components simultaneously. It provides real-time process control of moisture over a range of levels down to 4 parts per million or 2% of the reading, whichever is greater, based on the moisture level requirements of a drying chamber.

Source: Ametek Process Instruments

About the Author

John Wallace | Senior Technical Editor (1998-2022)

John Wallace was with Laser Focus World for nearly 25 years, retiring in late June 2022. He obtained a bachelor's degree in mechanical engineering and physics at Rutgers University and a master's in optical engineering at the University of Rochester. Before becoming an editor, John worked as an engineer at RCA, Exxon, Eastman Kodak, and GCA Corporation.

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