Assay of free and total tocainide by high performance liquid chromatography (HPLC) with ultraviolet (UV) detection

A rapid high performance liquid chromatographic (HPLC) method for the determination of tocainide, using N-(2,6-dimethylphenyl)-2-amino-butanimide as an internal standard, was developed. A methylene chloride extraction involving salting out at pH 9.0 was employed. An 85:15 mixture of 0.025M monobasic potassium phosphate at pH 3.0 and acetonitrile was used as the mobile phase. The separation and quantitative analysis of tocainide was performed on a mixed phase column with a 1.0-mL/min flow rate and detection at 210 nm. Separation of tocainide from some of its metabolites required the use of heptane sulfonic acid as an ion-pairing reagent. For the free-drug assay, the specimen was centrifuged through an Amicon Centrifree filter before being processed.