Why and how to reference chemical vendors in paper
Just do it in the experimental section, in text, without an endnote.

"The starting materials were X% stuff and Y% other stuff (cation  basis,  Aldrich  Chemical  Company, USA).  Vendor  supplied  ICP showed the following major impurities: Z ppm blalba, W ppm blablabla."  (I have seen master batch numbers listed as well.)

The main thing is to share enough info so that someone can repeat the work or can find a flaw if there was one.  For example if 5 9s purity is important, at least list that (probably make a comment to that effect as well).  If you had relatively low purity or possible impurities that may affect your results, just be honest and disclose it. (Feynman, Katzoff advice on sharing possible limitations of the research.)  

However, I think for routine synthetic chemistry, probably well into the high 90s% of experiments are not really dependent on the starting materials.  That is, it is possible to get sufficient purity relatively cheaply and the experiment is more about what you decided to do and the methodology.  But there may be cases where this is not true or where your results are particularly noteworthy.  All that said, synthetic chemistry, in my experience has very low replication problems.  It's just not like priming research.

EDIT:  Just noticed you had a 1, 2 format.  I believe I address both questions.