washing pump flanges and accessories. How?

Hello lovely mamas! I'm a ftm here and my babygirl is a micro preemie born at 23 weeks 2 days. She's doing wonderful in NICU so far.

I've been pumping and will be getting discharged soon and been looking into soaps to wash the pump flanges and accessories with. I was told to use pure Castile soap but upon browsing online none are completely JUST castile! A little help please.What do you use?

Because baby is so delicate only want to use the best stuff out there.

Thank you! xoxo