Plastic accessories like pipette tips or multiwell plates are widely used for endotoxin testing. The harmonized Pharmacopoeias require that any plastic consumables have to be free of detectable endotoxin and - equally important but often not considered - they must be free of interfering factors. That means this is a global requirement. Lonza offers pre-screened and certified accessories, but if specific items have to be used, we have a guideline for how consumables can be qualified for endotoxin testing.
The most crucial portion of the pipette tip is the part coming into contact with the solution to be dispensed. Therefore, it can be used to draw in and dispense water for BET essentially mimicking how the tip is actually used in the test. Instead of pooling solutions, we suggest rinsing a number of tips with the same water to lower the solution volume and thus allow the tips to be tested at a low endotoxin limit. Another important consumable is the multiwell plate. For the 96-well plates, we want to avoid hot wells and will apply a similar limit as for the tips. We suggest testing the plates also with a procedure that mimics how they are used in BET, for example utilize water for BET in most of the wells and a few wells as positive controls. Evaluation of the plates is based on the reaction times.
When screening items from a new vendor a more extensive protocol may be required, including testing three different lots. In addition, it is important to remember that not all plastic is the same. Different types of plastic have different characteristics and due to production procedures, there will be variability from vendor to vendor and from lot to lot.
The complete article including detailed examples, protocols and calculations can be downloaded free from the QC Insider® Toolbox.
Written by SST
