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  • Laser Technique Analyzes Pharmaceuticals

Photonics Spectra
Dec 2001
Brent D. Johnson, Senior News Editor

Lot consistency is a major concern in pharmaceutics. Constant testing of batches of tablets and capsules as they emerge from the production line ensures that patients receive a regular dosage that falls with-in a standard deviation of 5 percent.

High-performance liquid chromatography has been the traditional tool for assessing blend uniformity; however, this process is somewhat lengthy, requiring the sample to be dissolved in solution.

Merck & Co. is experimenting with the new PharmaLibs system from Pharma Laser that competes with both wet chemistry and near-infrared spectroscopy for determining sample content. The test can be performed in less than a minute.

Laser-induced breakdown spectroscopy could enable in-line pharmaceutical analysis. Merck is evaluating the PharmaLibs system for measuring uniformity and excipients in tablets and capsules in pharmaceutical manufacturing. The inset (bottom) shows the laser-induced plasma.

PharmaLibs uses the laser-induced breakdown spectroscopy process, in which pulses from an Nd:YAG laser at 1064 nm cause a photochemical and photothermal breakdown in the sample, generating a plasma. The plasma excites excipient atoms in the sample, and the light they emit is transferred via a fiber optic bundle to a gated CCD camera. The emission line intensities provide information about the presence and concentration of active ingredients, lubricants, disintegrants, binders and other ingredients that affect the performance of drugs.

Mark Mowery, a senior research chemist at Merck, said that PharmaLibs rapidly measures uniformity and excipient assays in-line. Although he doesn't believe that the high-performance liquid chromatography technique for composite assay and degradate testing will go away anytime soon, he said laser-induced breakdown spectroscopy has potential for in-line analysis.

"We are evaluating whether it can replace some existing techniques," Mowery said. "It definitely has its uses."

He also said that the system is straightforward and doesn't take a lot of time to get up and running.

The primary disadvantage of laser-induced breakdown spectroscopy is that, because it relies on atomic emission, the sample species of interest must contain an element that is unique to the sample matrix.

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