Exploiting a Microdisk Array Device for Enhanced Microextraction of Indomethacin from Human Urine

A novel microdisk array (MDA)-based microextraction approach was developed and applied for the determination of indomethacin in human urine prior to HPLC–UV analysis. The MDA represents an innovative, reusable extraction format that combines miniaturization with an array-based architecture to enhance mass transfer while minimizing sample handling and solvent consumption. The device was constructed by concentrically mounting two C18 microdisks onto a stainless-steel spinal needle secured with frit-based stoppers. Extraction was carried out by immersing the MDA device in 1500 μL of the aqueous sample for 20 min, followed by a brief water-rinsing step and desorption of the analytes in 1000 μL of a 50/50 (v/v) water/acetonitrile mixture. Key parameters affecting the adsorption and elution efficiency were systematically optimized. Under optimal conditions, the method showed linearity in the range of 50–1000 ng/mL, with a limit of detection of 14 ng/mL. The intra- and interday precision values were below 16.7%, and accuracy, expressed as relative recoveries, ranged from 91.4% to 108.7%. The environmental sustainability of the proposed method was assessed using the MA index, confirming its reduced environmental footprint. The practical applicability of MDA-based microextraction was demonstrated through the successful analysis of urine samples collected after oral administration of indomethacin-containing pharmaceutical products.