One area my company and one of our CMOs need help with is passivation. One of our CMOs needs to perform passivation with a nitric acid solution to help with a yield issue and impurities. However, they have stated that their process cant ensure low enough levels of nitric acid to a ppb level. Does anyone have experience with this? The company said passivation with citric acid is not adequate but they are concerned that low levels of nitric acid could lead to nitrosamines with these materials as at least one contains a piperidine ring in its structure. Does anyone have recommendations for a company who we can use to contract the passivation and cleaning work?