Research Article

Separation of Cyclic Dipeptides (Diketopiperazines) from Their Corresponding Linear Dipeptides by RP-HPLC and Method Validation

Figure 2

HPLC chromatograms of 1 mM standards of (a) cyclo(L-Arg-L-Arg) at 10% MeOH, 268 nm; (b) L-Ala-L-Ala and D-Ala-D-Ala, L-Ala-D-Ala, cyclo(L-Ala-D-Ala) and cyclo(L-Ala-L-Ala) and cyclo(D-Ala-D-Ala) at 10% MeOH, 210 nm; (c) L-Phe-L-Asp, L-Asp-L-Phe, L-Phe and cyclo(L-Asp-L-Phe) at 20% MeOH, 210 nm; all separations were performed at: 20°C column temperature and 0.7 mL min−1 flow rate.