Development and validation of high-performance liquid chromatographic method for the determination of folic acid

A high-performance liquid chromatographic (HPLC) method with ultraviolet detection at 278 nm is presented for the determination of folic acid with 5-hydroxyindole-3-acetic acid as internal standard. Chromatographic separation was based on ion-pair HPLC with tetrabutylammonium hydroxide as the ion-pairing compound. The method is sensitive, lower limit of detection was 0.1 ng/ml, the limit of quantitation was 0.25 ng/ml, using a 25-microliter sample volume. The systems precision intra- and interassay CVs for folic acid were 1.4% and 2.5%, respectively.