I AM HAVING PROBLEM IN PREPARATION OF GRAPHITE SOLUTION AFTER READ THE JOURNAL. CAN SOMEONE HELP ME?

THE JOURNAL EXPERIMENTAL METHODS IS WROTE IN THIS WAY:
Sodium cholate (NaC) was purchased from Sigma Aldrich and was dissolved in Millipore water at various concnetrations between 0.01 and 20mg/mL. Graphene dispersions were prepared by adding graphite at an initial concentration of 5mg/mL[/COLOR] to 400mL NaC solution in 500mL capped round-bottomed flasks. Various surfactant concentrations were explored.

I have no idea hw to prepare this solution based on this procedure. Can some one explain it to me?