Tween 20 is 20 mole ethoxylate of sorbitan monolaurate and Tween 80 is 20 mole ethoxylate of sorbitan mono oleate. Only difference is in hydrophobe. Tween 20 has lauric acid and Tween 80 has oliec acid in hydrophobe. Both are nonionic surfactant. They are used as solubliser, O/W emulsifier and detergent for shampoos.

Lauric acid has some antimicrobial potential. Tween 20 includes about 60% monolaurate and some free lauric acid - more as it ages. Bacterial esterases can liberate additional lauric acid. In microbiological testing, use Tween 80 when possible rather than Tween 20.

Thanks Phil, yes I use Tween 80 as a neutralizer for the antimicrobial fabrics I test but using it in my inoculum carrier would totally kill the purpose of letting the fabric be in contact with the bacteria. What other surfactant would you suggest using to help me inoculate hydrophobic fabrics?

The treated fabric repels water? Makes it tough as using a surfactant simplifies the test but leaves the findings of questionable relevance to real life. Arlacel has been used as for preservative neutralization - esp. for fine cosmetics - but as with your valid concern for Tween 80, may mitigate antimicrobial effect within the assay. Understand you want a relevant microbe applied evenly, reproducibly and intimately to the fabric surface in a manner relevant to anticipated real life application. Can you inoculate via a thin layer of tempered agar? You could check for ASTM or ISO protocols and those would be more defensible to regulatory bodies. But I offer the caution that these are generally not validated - just the best thing a committee compromised to put on paper without every having run the method.

Thank you very much, it does repel water. I am thinking on running some tests before, using the same fabric without the hydrophobic treatment with a normal aqueous inoculum and with an inoculum on an agar-added carrier to try what you suggested. I'll see if I can get similar counts from both samples.

Hi. I think that tween 20 or 80 has the same action if it just used as a surfactant to make the cells disperrsed in the solution in homogenous mannar. But, to test the antibacterial effects of them, you may make small test against the used bacterial strains.