Small blood volumes from children for quantitative sotalol determination using high-performance liquid chromatography

A sensitive high-performance liquid chromatographic method using fluorescen ce detection has been developed for sotalol determination in small plasma s amples of children and newborns with limited blood volume. In sample sizes of 100 mul of plasma, sotalol was extracted using an internal standard and solid-phase extraction columns. Chromatographic separation was performed on a Spherisorb C-6 column of 150 x 4.6 mm I.D. and 5 mum particle size at am bient temperature. The mobile phase consisted of acetonitrile-15 mM potassi um phosphate buffer (pH 3.0) (70:30, v/v). The excitation wavelength was se t at 235 nm, emission at 300 nm. The flow-rate was 1 ml/min. Sotalol and th e internal standard atenolol showed recoveries of 107 +/- 8.9 and 97 +/- 8. 1%, respectively. The linearity range for sotalol was between 0.07 and 5.75 mug/ml, the limit of quantitation 0.09 mug/ml. Precision values expressed as percent relative standard deviation of intra-assay varied between 0.6 an d 13.6%, that of inter-assay between 2.4 and 14.4%. Accuracy varied between 86.1 and 109.8% (intra-assay) and 95.4 and 103.3% (inter-assay). Other cli nically used antiarrhythmic drugs did not interfere. As an application of t he assay, sotalol plasma concentrations in a 6-year-old child with supraven tricular tachycardia treated with oral sotalol (3.2 mg/kg per day) are repo rted. (C) 2001 Elsevier Science B.V. All rights reserved.