How to perform metal detection in pharmaceuticals processes

How to conduct challenge testing of metal detector sensitivity?

You should conduct in-line metal detector challenges at the beginning of the process equipment running.

Each challenge should consist of three passes of the challenge disc/cylinder through the aperture. Such in-process challenge tests should be performed and documented at a minimum information of:

– Lot/batch number to start-up

– After re-starting equipment (e.g., after breaks, shift changes, or downtime exceeding two hours); and

– At the end of a batch/lot.

– Challenge metal detectors used in manufacturing operations with discs/cylinders containing spherical 0.5mm ferrous, 0.5mm non-ferrous, and 0.8mm stainless steel metal

– Challenge metal detectors used in packaging operations with discs/cylinders containing spherical 1.0mm ferrous, 1.0mm non-ferrous, and 1.5mm stainless steel metal

How is the metal detected and what to do next?

Metal detectors have built in sensors that can detect metallic particles such as fine particles, corrosions, pins, buds, flakes etc. through electromagnetic induction mechanism, radio signals transmission etc.

Your products and raw materials can be contaminated by unwanted equipment failures, metal-to-metal contact or metal introduced by rusty and dusty environments.

Metal detectors are equipped with audible and/or visual alarms. Production Operators in the vicinity of the equipment should be signalled when metal is detected, and the in-process goods are diverted or isolated.

1. In-process control

You should establish in-process control (IPC) limit for the number of units isolated for each process or product. Any excursions from the in-process control limit should be evaluated during processing.

Note: This in-process control limit during processing is separate and distinct from the end of processing action limit.

2. Action limit determination

Action Levels for the total number of units (e.g., tablets, capsules, bottles) isolated by the metal detector should be developed by the quality team based on but not limited to:

i. Historical data on the number of units contaminated with metal according to product and/or manufacturing or packaging process step

ii. Investigation reports [e.g., deviation reports including any documented product recovery from contaminated units, and

iii. Applicable quantitative results indicating that preventive measures have reduced metal contamination in manufacturing and/or packaging process steps. Such preventive measures include and are not limited to:

– Installation of rare earth magnets at raw material charging stations;

– Raw material process improvements by the vendor that reduced contamination; and

– Manufacturing or packaging equipment set-up improvements that reduced contamination resulting from equipment wear.

3. Investigation

You should investigate and document if the quantity of units isolated by the metal detector exceeds the action limits. The lot should not proceed to another processing step until the quality team reviews the investigation report and determines the status of the lot.

Product units (e.g., tablets, capsules, packaged units) that are isolated by the metal detector should not be returned to the acceptable units unless an investigation reveals an assignable cause.

Such product units should be placed in quarantine-Hold status pending the completion of the investigation.

Product units that are found acceptable on re-inspection may be returned to the acceptable units of the lot being processed, with the approval of the quality team.

Re-inspection should be performed following a written and approved protocol or site standard operating procedure (SOP). Product units that are isolated by the metal detector during re-inspection should be rejected and not returned to the acceptable units.

Such rejected product units should be collected in a dedicated container that is properly labelled as to its contents (e.g., “Metal Detector-Rejects”).

Accountability of units with metal contaminants should be summarized in the investigation report when a process deviation causes metal contamination.

Rejected units may be dissolved in a solvent and evaluated to determine metal type and source, if feasible, as part of the investigation.

Accidental introduction of metal during a process step should result in the process immediately being stopped and an investigation conducted. The operation should not continue until the quality team has reviewed the investigation and approves continuing the process.

Summary

There are many types of metal detections used in pharmaceutical processes during raw material mixing, bulk preparation such as tableting, encapsulation, liquid formulation etc. Metal detectors also employed during packaging operations.

The location of metal detectors in your process will depend on critical processing steps and historical contamination data. As a prevention from metal contamination iIt is important keep your environment free from rust and dust.

Metal detectors need to be trained and challenged before employed in your process to avoid false alarms. 

You should investigate all metal contamination incidents properly, determine the roost cause and implement preventive actions to stop recurring incidents in future.