I'm not sure what's in the buffers. When I checked the Seachem website, they didn't come right out and state the ingredients. The best I could find were the MSDS sheets.
The Acid buffer is listed as "Proprietary powdered bisulfate salts": http://www.seachem.com/support/MSDS/AcidBuffer.doc.pdf
The Alkaline buffer is listed as "Proprietary powdered non-phosphate buffer salt": http://www.seachem.com/support/MSDS/...Buffer.doc.pdf