Near-IR Inspects Tablets, Pills

When you take medication, are you sure you are getting the right pill? Brimrose Corp. of America (Baltimore, MD) has developed a line of acousto-optic tunable filter near infrared (AOTF- NIR) spectrometers that, among other uses, ensure that the right pill goes into the right vial at phar-maceutical plants. Brimrose has sold dozens of online systems to pharmaceutical manufactur-ers such as Pfizer, Merck, SmithKline Beecham and others to inspect pills and bulk powders. The spectrometers are also used to ensure proper powder blending, which Brimrose believes offers environmental advantages—real-time blending reduces rejected batch frequency, avoiding the need to dispose of pharmaceuticals as waste.

On production lines, Brimrose's spec-trometers analyze roughly 25 pills per second as the pills pass by on the packaging line. Conventional inspection spectrometers read about two pills per second. Through a recently announced collaboration with the Ballistic Missile Defense Organization (Washington, DC), however, Brimrose expects processing improvements to increase this capability to 100 pills per second.

AOTF NIR

An AOTF is an optical device that uses ultrasonic waves to alter the index of refraction of an optical crys-talline medium. The spectrometer obtains data in the near infrared (NIR) with a high degree of wave-length resolution in near-real time. AOTFs have several advantages over mechanical spectroscopic systems based on rotating devices or moving mirrors, but the benefits most desired by pharmaceutical manufacturers are speed and accuracy. A well-tuned AOTF can scan the NIR spectrum more than 30 times per second, compared to conventional spectrometers which scan a range of interest only once per second.

How AOTF NIR works

AOTFs have made their mark in many manufacturing scenarios, including the food and chemical industries as well as pharmaceuticals. The information they provide can increase production efficiency, reduce batch and material waste, and ensure product quality. For example the starch, protein, liquid, and fiber concentrations of grains, octane numbers of gasoline, moisture content of chemicals or food, or the lignin content of pulp and paper can be determined through NIR analysis. What's attractive about NIR is that it can handle real-life industrial monitoring applications in which samples are moving, inhomogeneous and may experience sudden changes in compositions and optical characteristics.

For a tablet production line, for example, measurements need to be performed rapidly to derive accurate compositional or quality parameters. A large number of measurements may need to be averaged to correct errors. Also, data may need to be recorded at multiple wavelengths in real time, preferably simultaneously. For this application, the spectrometer must be able to be tuned repeatedly to precise wavelengths reliably over long periods of time. In addition, the spectrometer must be rugged, compact, flexible, and simple to operate. Problems in meeting these requirements with classical spectroscopic technologies have limited the deployment of NIR spectroscopy in industrial and commercial applications.

Although instruments using other technologies have been successfully used, AOTF is unique in its ability to satisfy all the criteria for hands-off real-time NIR spectroscopy in the industrial environment. With the advent of rugged, compact, fast spectrometers based on AOTF technology, Brimrose hopes that NIR spectroscopy will soon fulfill its promise as an important online diagnostic tool.

"AOTF NIR spectrometers can look for whatever you teach it to look for," said Gabriel Levin, operations manager at Brimrose. "Customers use these instruments to verify composition, product identification, product presence—in other words, is it there?—as well as color and shape. For pharmaceuticals we usually stay away from the strictly visual applications, with the exception of barcoding. One of our products, the Luminar 2050 model, analyzes products and simultaneously inspects barcodes to assure that the right tablet is going into the right vial."

Brimrose NIR analyzers feature familiar Windows 95 or -NT interfaces

NIR's ability to quantify ingredients makes it ideal in pharm manufacturing environments involving different dosages. "We have products that can differentiate between tablets containing 2, 5, and 10 milligrams of active," Levin stated. "We can also check on inactive ingredients in any dosage form, including powders and liquids. Since NIR radiation passes through glass and plastic, real time inspection is possible for already-packaged drugs, even in blister packs—provided they're not metallized."

Levin explained that other optical techniques have been tried for pharmaceutical inspection. Mid-IR, which every pharmaceutical chemist has used in school or on the plant floor for compound identification, does not penetrate tablets. White light, from which NIR data can be extracted, heats tablets up and may interfere with stability. "Preselected NIR, with its much shorter wavelengths [10,000 to 4,000 wavenumbers] doesn't heat the product and works in both transmission and reflectance mode," said Levin. "Furthermore it works in real manufacturing environments. Ambient light does not affect analysis, so you don't need a closed compartment. Vibration and positioning are not critical either, which is important for analyzing small objects such as tablets and pills."

For more information: Gabriel Levin, Operations Manager, Brimrose Corporation of America, 5024 Campbell Blvd., Baltimore, MD 21236. Tel: 410-931-7200. Fax: 410-931-7206.