First of all, if after all this time electric chair and lethal injection were not found unsuitable, I have zero faith this one would be (at least for the right reasons) regardless of botched attempts.
Second of all, I don’t advocate for our corrupt governments to handle executions. I 100% agree they can’t be trusted with this.
But there is no issue with the method itself, which is what this article is about and I am commenting on. Purity of the gas? What for? Unless there is so much oxygen the patient survives, it should not matter. Certainly not any trace amount you would have in industrial nitrogen supply.