Nickel-iron layered double hydroxide nanostructures for micro solid phase extraction of nonsteroidal anti-inflammatory drugs, followed by quantitation by HPLC-UV

Layered double hydroxides (LDHs) of nickel and iron were hydrothermally prepared by co-precipitation using urea hydrolysis. The Ni-Fe LDH nanostructures were characterized by X-ray diffraction, FT-IR spectroscopy, scanning electron microscopy, thermogravimetric and energy dispersive X-ray analysis. The LDHs are shown to be a viable sorbent for micro solid phase extraction by packed sorbent of the nonsteroidal anti-inflammatory drugs (NSAIDs) diclofenac, ibuprofen, mefenamic acid and naproxen from human urine. Adsorption and desorption parameters were optimized using a central composite design. Following desorption with a methanol/water mixture (95:5 v:v) containing 0.1% formic acid, the NSAIDs were quantified by HPLC with UV detection. Under the optimal conditions, response is linear in the 10-1000ng.mL(-1) NSAID concentration range. Limits of detection and intra-day and inter-day RSDs are <10ng.mL(-1) and 10.2%, respectively. The method was successfully applied to the determination of NSAIDs in some positive human urine samples. Relative recoveries from spiked samples range from 94.8 to 113%.