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Any clue on validation of a glassware washing machine?

Updated: Aug 10, 2023

Every company comes up with an approach how to handle glassware washing machine qualification. If it's a new company, somebody definitely has their recollection about how they did it in their previous company; if it's not a new company - well, it already has its own traditions, hasn't it? :)

Let me share my thoughts, but then let me share a hidden' treasure' of a guidance (however that I don't fully agree with it, it contains some really valuable direction).


In your URS, you want to specify what kind of glassware you want to clean routinely - it's just a list, maybe with capacity, as well. For this purpose, the suppliers should come up with turnkey solutions for your requirements.


You just need to evaluate if the solution provided meets your needs, and you have everything to operate - water, space, etc.


When you have your washing machine installed, you just make sure you have everything: the piece of equipment, all the connections, all the solvents you are to use.


This is where the qualification should be straightforward: apart from the EHS-related stuff (during the washing cycle the instrument cannot be opened, etc.) you want to make sure that the programme configured is able to clean in its full ability. What does this mean? I believe it means two requirements:

  1. it is capable of eliminating stains/residues from the glassware

  2. it is also capable of regaining the pH of residual washing agent to 7.0

The 1st requirement can be proven with 'reference stains' commercially available, the 2nd one is easy to control with a pH-meter from the drained water.


And what should the PQ be? This is always about checking against your original URS requirements: so you should test it against your least soluable material to clean.

But what should be the plan? how should we calculate the limit to achieve?

So this is where I would steal the approach from the EDQM document hidden among some others, running under the title Management of Volumetric Glassware (Annex 2).

So how I would solve this? Let me (almost) exactly Copy-paste from the guidane:

  1. The laboratory chooses an available “difficult to clean” API [least soluble in water I would evaluate]

  2. From the volumetric flasks described in the testing method of the selected API, two of the lower and two of the maximum nominal volume flasks are selected (e.g. 2 x 5ml and 2 x 100ml volumetric flasks)

  3. A reference solution of the API is prepared as described in the testing method

  4. Each of the selected volumetric flasks is filled to about 10% of its nominal volume with this reference solution, closed and shaken so the inner walls of the flasks will be covered by the liquid. They are emptied and allowed to dry

  5. The 4 flasks are then washed alone in the washing machine using the defined washing instructions (Empty Load) [I don't think this step is needed]

  6. The same procedure is performed with the maximum number of volumetric flasks that can be washed in the washing machine (Full Load)

  7. All the flasks are filled with the solvent solution used for the preparation of the Reference Standard Solution and analysed with the HPLC testing method of the API used (the method is validated and the validation parameters, e.g. LOD, LOQ etc. are used)

  8. No traces of the API above the LOD of the method should be detected.

However I don't agree with some other declarations from the guidance, I think this is a really good approach to perform the PQ of the washing machine.

Periodic requalification

How can you prove your glassware washing machine still performs in a proper way?

Once you proved during your PQ (using perhaps expensive reference materials or fractions of batches) that if your OQ elements work out well you get everyting you need - you would only need to repeat your OQ elements as part of your requalification: get rid of the 'standard stain', and rinse everything back to neutral pH. With this approach, however you contradict the requirements of the EDQM guideline, based on risk assessment, you can still keep everything under control.

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