Rinsing membrane filter

Why we rinse / wash / flush Membrane Filters during sterility Testing/ water Analysis /MLT analysis?

This is done to remove any product residue on the membrane. Product residue might inhibit microbial growth.

If we test the same product by pour plate method we can not wash it the entire product is in contact . How can we explain it ?

membrane filtration is used for larger sample volumes, may be up to several litres per membrane. the concentration of remnants on the membrane may inhibit growth, even if it is just glucose. That’s why the rinsing is done. pour plate is performed using max 1 mL of sample, so concentrations are much much lower and inhibition is not an issue unless for preservatives.

When pack size is small about 1 ml for vials and ampoules we still flush the membranes .

small pack sizes could still contain product with high concentrations. I would always recommend rinsing. The pharmacopeia do not state a no-rinse test, so getting authorities to accept a no-rinse test might be a challenge.

But I think while we using filtering method and when we see the structure of filter paper it is in zigzag form like a spider net…we have to open filter paper pores so that we got our positive result.

zigzag? how? what kind of membrane are you using?

0.47micron filter paper…
Made by Pall
Zigzag means filter paper structure. I mean when you elaborate its structure the structure of paper is of zigzag form to entrap Microbes

Instead of wash, can we use antimicrobial agent to inhibit the anti microbial activity of product

I would not recommend a folded membrane (are these even available sterilized?) . This would increase the amount of membrane handling required to properly place it on a solid medium and seriously increase the risk of false positive results. Use membrane disks instead.

Antimicrobial agents may be used in bioburden testing as prescribed in the pharmacopeial monograph (as a component of the wash solution). Suitability must be demonstrated and documented.

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