Impurity analysis of phenoxymethylpenicillin potassium salt (penicillin V potassium, CAS 132-98-9) according to the Ph. Eur. monograph, on an ARION® Plus C18, 3 µm column (150 mm × 4.6 mm, ARI-5720-IK46). Gradient elution with (A) phosphate buffer pH 3.4 : methanol : water (10:30:60 V/V/V) and (B) phosphate buffer pH 3.4 : methanol : water (5:60:35 V/V/V) at 1.5 ml/min and 50 °C, DAD detection at 254 nm. Impurity B, impurity D (4-hydroxyphenoxymethylpenicillin), impurity E (sum of isomers), the epimers F1 and F2 and the main phenoxymethylpenicillin peak are all resolved within 10 minutes.