Stuart Preston, business development manager, Mettler Toledo discusses how in pharmaceutical manufacturing, contamination control begins long before products reach final packaging.
Mettler Toledo
Raw materials are blended, milled and granulated before being compressed into tablets or filled into capsules. At each stage, there is potential for metal contamination arising from broken sieves, worn equipment, magnets or foreign material introduced with ingredients.
Metal detection forms part of the control strategy applied during these processes. By identifying and removing metal contaminated products while they are still in production, it aids compliance with regulations plus supports quality management within validated and documented systems.
Why are metal detectors used in pharmaceutical production?
As medications are used directly by individuals, even a small metal contaminant within a tablet, capsule or powder can present a risk to patient safety and product quality. Applicable Good Manufacturing Practice (GMP) requirements, including 21 CFR Parts 210 and 211, require manufacturers to establish appropriate controls to prevent contamination and deliver product quality. Where automated systems are used, GAMP 5 (Good Automated Manufacturing Practice) provides guidance on validation and lifecycle management.
Metal detection provides an automated inspection method capable of identifying stainless steel, ferrous and non-ferrous metal contaminants, including very small particles. In pharmaceutical applications, stainless steel detection sensitivity can reach down to 0.3 mm test spheres, depending on the product and configuration. At this level of sensitivity, inspection plays a vital role in physical contamination control.
Inspection before compression: powders and granules
Active Pharmaceutical Ingredients (APIs) and excipients are handled as powders or granules before tableting or encapsulation. During blending, milling or granulation, metal contaminants may be introduced through equipment wear or raw material handling.
Pharma Gravity Fall (GF-PRO) metal detection systems are designed specifically to inspect these free-flowing materials at vertical transfer points. As powders move by gravity through an enclosed chute, they pass through the detector aperture. If metal contamination is identified, a fast-acting reject mechanism diverts only the affected material from the product stream.
By positioning inspection before compression, metal contaminated material can be removed early in the process, reducing the likelihood of a full batch being affected.
Inspection after compression: tablets and capsules
Once powders have been compressed into tablets or filled into capsules, inspection shifts to the finished dosage form before packaging.
Tablex-PRO is a pharmaceutical metal detection system from Mettler Toledo designed specifically for solid-dose applications. It integrates directly with tablet presses or encapsulators and de-dusters, to inspect products immediately after formation. As tablets discharge from these machines, they pass through the metal detector and are automatically separated into accepted and rejected streams.
Inspection can take place at speeds of up to 300,000 tablets per hour, depending on the application. If a metal contaminant is detected, a minimal number of tablets or capsules are diverted into the reject container by the fast-acting reject device. This rejection approach helps minimise product loss while maintaining tight process control. A lift flap diverter reject mechanism offers straight-line product flow for delicate products; a side diverter reject mechanism is ideal when inspection height space is restricted.
Blister packs are not typically inspected using conventional metal detectors at this stage because aluminium foil interferes with the detection field. For that reason, inspection is generally focused on unpackaged powders, tablets and capsules.
How do pharmaceutical metal detectors work?
Pharmaceutical metal detectors operate using balanced coil technology. A high-frequency electromagnetic field is generated within the inspection aperture. When metal passes through this field, it disturbs the signal and is detected by the system electronics.
Ultra-high tuned frequency operation, combined with an optimised aperture size, enhances sensitivity particularly for non-magnetic stainless steel contaminants, which can be more difficult to detect.
When contamination is identified, visual alarms are activated and the reject mechanism diverts the affected product. These events are recorded to provide documented evidence of removal.
Compliance, validation and lifecycle control
In pharmaceutical environments, detection capability alone is not sufficient. Inspection systems must operate within validated frameworks and be supported by documented performance. Metal detection equipment is supplied with documentation to support Installation Qualification (IQ), Operational Qualification (OQ) and Performance Qualification (PQ) as part of the wider Equipment Qualification (EQ) process. Ultimately, the EQPac documentation from Mettler Toledo allows the manufacturer to have a traceable procedure for implementing the metal detection system into their production line.
Validation and verification activities continue throughout the system lifecycle. Regular sensitivity checks, including Performance Monitoring Routine (PMR) testing, annual performance verification and scheduled revalidation form part of standard site procedures. Systems also maintain controlled records of user access, configuration changes and test results, with reports available via Ethernet or USB to support audit readiness and traceability.
Trained service engineers can also support installation, validation and ongoing maintenance, helping manufacturers maintain consistent inspection performance over time.
Design considerations in pharmaceutical environments
Pharmaceutical production areas are tightly controlled and often space is constrained. Metal detection systems must combine compact design with flexibility to integrate with different tablet presses, de-dusters and transfer points. Adjustable configurations allow the system to accommodate varying tablet sizes and product formats. Flexibility is enhanced with adjustable aperture / reject device height and castors which allow the system to be easily repositioned to integrate with other in-process equipment.
Hygienic design in pharmaceutical environments focuses on cleanability. Mirror-polished, stainless steel construction, smooth surfaces and simplified strip-down procedures support controlled cleaning processes. Touchscreen interfaces and password-protected access contribute to ease of use and controlled operation.
Conclusion
Metal detection remains a core inspection technology within pharmaceutical manufacturing. By inspecting APIs, excipients, tablets and capsules at critical stages, manufacturers can detect and remove metallic contamination before products progress further through production.
In an industry defined by compliance, documentation and patient protection, metal detection supports reliable inspection, validated performance and controlled process management across the system lifecycle.