Batch-to-batch variation of retention times for cytochrome c using 20 cm × 100 μm I.D. monolithic poly(butyl methacrylate-co-ethylene dimethacrylate) capillary column prepared using thermally (A, B, and C for batches 1–3, respectively) and photochemically (D, E, and F for batches 1–3, respectively) initiated polymerization. Each batch consisted of 5 columns and 15 separations were carried out with each column. For experimental conditions see Fig. 2.