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.