Impact of sorbent particle size on the separation of a 2–30 mer oligodeoxythymidine ladder. The separation was performed using an XTerra MS C18 30 × 4.6 mm column packed with 2.5 μm (A), 3.5 μm (B), and 5 μm sorbent (C). The flow rate was 0.5 ml/min, and the column temperature was 50 °C. Mobile phase A: acetonitrile—0.1 M TEAA, pH 7 (5:95, v/v). Mobile phase B: acetonitrile—0.1 M TEAA, pH 7 (20:80, v/v). Gradient starts at 26.7% B (9% ACN); at 20 min it reaches 53.3% B (13% ACN). The gradient slope was 0.2% of acetonitrile per minute (0.4% per milliliter) (reprinted from Ref. [12], copyright 2021 with permission from Elsevier, license number 5177001267055).