Hello.
Yes, in a Broadway it is necessary to have PCM stream in class 12th basically it will not be counted during admission but the basic eligibility criteria for getting into MSc analytical chemistry says that a candidate must have at least 50% aggregate from any recognised University with physics and Chemistry as a compulsory subject in the graduation, you can only have physics and Chemistry subject in your graduation when you belongs to PCM stream in class 12th, overall it is necessary to have PCM in 12th.
Best of luck.