Determination of indometacin and acemetacin in human urine via reduced graphene oxide - based pipette tip solid-phase extraction coupled to HPLC

A rapid method for solid-phase extraction (SPE) and quantitation of the non-steroidal anti-inflammatory drugs indometacin and acemetacin in urine was developed. SPE is based in of the use of a reduced graphene oxide (rGO) in a pipette tip, and separation and quantitation is based on HPLC with a Promosil C₁₈ column and UV detection. The amount of sorbent, types and volumes of washing solvent and elution solvent were optimized. The results showed that the use of the rGO sorbent and a miniaturized pipette tip cartridge are distinctly superior to other sorbents including multiwalled carbon nanotubes and conventional SPE cartridges. Linear responses to indometacin and acemetacin are found for the 0.1–50 μg mL⁻¹ concentration ranges, recoveries (at three spiking levels) range from 89.6 % to 95.7 %, and the relative standard deviations are ≤6.4 %.