Chemists get trained to work with dangerous substances, that's a core part of the job. But Dimethylmercury is something else, it's far more dangerous than anyth

Chemists get trained to work with dangerous substances, that's a core part of the job. But Dimethylmercury is something else, it's far more dangerous than anything else someone in that field would ever encounter. NMR is usually a pretty boring field in terms of stuff killing you. The most you can usually expect is someone sealing an NMR tube with something still reactive inside, which might blow up the glass tube at a later point. That tends to annoy the people managing the NMR spectrometers, so there are usually rules and procedures that should eliminate that risk. Of course you examine all kinds of substances by NMR, so my previous statement is kinda wrong. If you work with really toxic substances, you also want to analyze them and put them into an NMR spectrometer. A huge difference here is whether you're regularly working with really dangerous substances or not. Many substances in chemistry are dangerous, but they're the kind of dangerous that every chemist is supposed to be trained for. But there is an enormous differences between a regular dangerous chemical and something like Dimethylmercury where a few drops through a nitrile glove can kill you. That needs an entirely different level of precautions than the ones you usually have in the lab. And it's the kind of danger that simply isn't worth it for most cases. If you're used to work with truly dangerous substances you can probably handle somethign like this safely, but the real danger is when people used to working with medium dangerous substances handle a truly dangerous substance like this without being really aware of the extent of the danger. That chemical is simply far too dangerous to be a calibration standard, and that's why it isn't anymore.