Speakers Support LIBS for Pharmaceutical Analysis

Philadelphia, PA (July 24)-Speakers introduced laser-induced breakdown spectroscopy (LIBS), an analytical technique largely unfamiliar to the pharmaceutical industry, to attendees at this year’s Pharmaceutical Technology annual conference*. Elizabeth Kwong, a senior scientific director at Merck Frosst Canada (Kirkland, QC, Canada), explained that LIBS has been used for decades in mining, metallurgy, and environmental applications. Her company collaborated with the National Research Council of Canada (Boucherville, QC, Canada) to develop LIBS for pharmaceutical analysis.

LIBS is a form of solid-state, atomic-emission spectroscopy that incorporates laser ablation and excitation. The technique uses elemental analysis to quantitate samples such as tablets and powder blends. It requires a target element unique to the sample. LIBS can provide a single test that identifies by species, location, and depth by species and distribution. In addition, the test can simultaneously analyze multiple components.

In the LIBS technique, a laser vaporizes a sample’s constituents before atomizing and ionizing them. Then the atoms and ions are electrically excited. As these particles relax, they emit light at characteristic wavelengths that enable them to be identified. The method is described in USP–NF General Chapter <730> and is used for finished-product testing and as an at-line process analytical technology (PAT) technique.

Kwong and her copresenter, André Blain, president of Pharma Laser (Boucherville, QC, Canada), described the various pharmaceutical applications of LIBS and demonstrated that it could be used as a PAT technique for process monitoring. Blain observed that LIBS was particularly helpful for out-of-specification testing and root-cause analysis. He said that manufacturers could use LIBS to analyze samples such as tablets and compare them against a reference standard.

The presenters added that LIBS could help improve the blending process in several ways. For example, LIBS can test finished products for blend uniformity, blend distribution, concentration, and the amount of active pharmaceutical ingredient and functional excipients such as lubricants and disintegrants. In addition, manufacturers can use LIBS to check blend uniformity among blenders as well as within individual blenders. Kwong and Blain also indicated that LIBS can be used to assess various aspects of tablet-coating, including thickness, photoprotection, and variability.

LIBS has many advantages for the pharmaceutical industry, according to Kwong. The method requires no solvents and minimal sample preparation, and it produces results in about 1 min. LIBS exhibits limited matrix effects compared with other analytical techniques, and its accuracy and linearity are comparable to that of near-infrared spectroscopy. The technique also can provide 3-D spatial resolution.

Kwong acknowledged, however, that LIBS is a destructive technique, which could be considered a disadvantage. She also observed that powders must be compressed for LIBS analysis, which entails additional preparation.

Kwong and Blain argued that LIBS’s speed, accuracy, and versatility justified its adoption by the pharmaceutical industry. They seek to gain wider acceptance for the technique within the industry and to establish it within the manufacturing environment. Although a validation strategy for the technique remains to be created, and other regulatory concerns must be addressed, the speakers argued that LIBS is a proven technique with many advantages and much potential for pharmaceutical manufacturing.

Pharma Laser is an independent company that created the “PharmaLIBS” unit to perform LIBS analysis. The fully integrated PharmaLIBS machine provides graphic and table results, 3-D distribution views, and complies with 21 CFR Part 11. The company is working to improve the instrument to provide flexible sample presentation and to make powder analysis easier.

*The 2007

Pharmaceutical Technology

Annual Conference was held in Philadelphia, Pennsylvania July 24–26.

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