On a student lab practical manual for extraction of plant pigments, under the reagent line it says: Prepare citrate-phosphate-borate-HLC buffer, pH 2,3,5, and 7. How to prepare this/these buffer(s)?
Basically, a buffer is a solution of compounds with 'resistance' to changing a particular pH value. It is not clear from your question whether it is necessary to have all of the compounds in the same solution. Practically, you would make a different buffer solution using the indicated reagents to 'buffer' at the desired pH. The following resources provide useful ranges, pKa's (used to calculate the compound concentrations for a particular pH) and short discussion of how to use those values.
