Determination of citrate – citric acid (CAS 77-92-9) and sodium citrate (CAS 18996-35-5) – in an infusion solution on an ASTRA® C18-HE, 5 µm column (250 mm × 4.6 mm, AST-5732-LM46). Isocratic elution with 20 mM phosphate buffer pH 2.0 : ACN 90/10 (v/v) at 1.5 ml/min and 30 °C, injection volume 2.5 µl, UV detection at 210 nm. The sample composition was citric acid monohydrate 3.27 g, sodium citrate dihydrate 26.3 g, glucose monohydrate 25.5 g and sodium dihydrogen phosphate monohydrate 2.22 g. On the ASTRA® C18-HE column the analyte gives a sharp peak at about 2 minutes, against a broader peak near 3.9 minutes on the competitive column (Competition S).