http://7mooowmp22dixrekvwclhjjzqfp4j64rqwq6ku6ftn4z3ea2mplcdaqd.onion
Secondly, you will need samples of all these substances (at the very least, their exact characteristics - dew point, boiling point, etc.). Thirdly, it will take a lot of time - at least a year (this is assuming that each poison will be given at least 40 minutes). All of the above, in principle, will only help if only one poison has been used, which has not been mixed with anything else.