2.3.5. High-Performance Liquid Chromatography (HPLC)

A reversed-phase HPLC method was developed and validated to quantify the concentration of FTS released from strings and 3D printed rings. The HPLC analyses were carried out with a Thermo Finnigan Surveyor HPLA, (Thermo Finnigan, San Jo´se, CA, USA) on an Intersil, ODS-3 column (4 µm, 4.6 Å ~150 nm (GL Sciences, Torrance, CA), maintained at 40 ◦C, with a flow rate of 1.0 mL/min, a 25 µL sample injection, and an acetonitrile/water mobile phase, each modified with 0.1% trifluoroacetic acid. A gradient method was utilized to achieve separation (0–20 min: 5–100% acetonitrile; 20–22 min: 100% acetonitrile; 23–25 min: 5% acetonitrile). Fluticasone was eluted at a retention time of 17.3 min. Data were collected at 265 nm and computed using Chromequest software. Concentrations were derived from a calibration curve generated using fluticasone standards prepared in 100% acetonitrile (250 µg/mL to 61 ng/mL).
