High-performance liquid chromatography with UV detection and diode-array UV confirmation of isonicotinic acid hydrazide in cattle milk

A method for the determination of isonicotinic acid hydrazide (isoniazid) in milk was developed. Milk was deproteinized with trichloroacetic acid. Isoniazid was condensed with cinnamaldehyde and assayed on a reversed-phase HPLC system, with good sensitivity and accuracy (10 μg/l) with UV detection at 330 nm. Use of solid-phase extraction with a C₁₈ cartridge allows the detection limit to be lowered to 0.1 μg/l with UV detection and confirmation of isoniazid hydrazone from the diode-array UV spectrum.