01/2007 | Credible Inspection

Patients must rely on pharmaceutical manufacturers to ensure that their medications contain precisely the stated quantity of material and active ingredients, so the industry’s quality control standards are very high. To achieve this, every pill is weighed after production on a separate machine. Now Bosch researchers have found a way for an integrated solution that is cheaper and within cycle times of less than a second even more accurate. They measure the intensity of an X-ray beam that has passed through a capsule. From the attenuation of the beam, they can calculate the exact mass in the sample, which makes it possible to dispense with the conventional process step of weighing the sample using a load cell.

The X-ray procedure is also simple to automate. The packaging machine fills a capsule with the substance, then passes it through the inspecting X-ray beam, and finally seals it. This method has now been perfected, and production will be launched this year by the Bosch Packaging Systems Business Unit.

The method is very accurate — so precise, in fact, that thickness variations in the bottom of a capsule are the main source of error. Each capsule is exposed to the X-ray beam for a quarter of a second, without affecting or changing the substance. This is enough time for the device to make 500 measurements. The active ingredient’s mass is derived from the mean value of these measurements. Each test measurement is followed by an automatic reference measurement, for continuous calibration of the system. The X-ray beam checks a material with a known attenuation value, to compensate for any drift in the method's sensitivity over time. As pharmaceutical companies produce large quantities of such capsules, a single-file inspection of all samples would take too long. This is why the researchers have created a multi-channel process. Up to 18 X-ray sensors operate simultaneously to assure rapid throughput. This technique can be used to inspect powders, pellets, microtablets, or mixtures of these forms.

But there is some variation in the precision of the results. The more coarse-grained the content, the more difficult is the test. Nevertheless, sufficient accuracy, and the benefits of an affordable, compact and fast-reacting inline inspection, are achieved. The system is housed in a shielded enclosure, so radiation cannot penetrate to the outside, and the X-ray intensity is so low that it has no effect on the medication, as confirmed by inspections conducted by in-house and independent external specialists. Patients can be confident: All capsules are tested 100 percent to ensure they hold the correct mass.