Acella

LC-APCI-MS analyzes were performed on an Acella chromatograph (Thermo Scientific); coupled to a triple-quadrupole mass spectrometer model TSQ Quantum Acess^® (Thermo Scientific), equipped with an Atmospheric Pressure Chemical Ionization (APCI) source, operated in positive mode with monitoring in the range of m/z 100–800. The mass spectrometer was equipped with Surveyor LC Pump Plus, Surveyor Autosampler Plus, Rheodyne injection valve (25μL), Luna C18 column (150 × 4.60mm, 5μm) (Phenomenex–Torrance, CA, USA), operating simultaneously with Surveyor PDA Plus diode array detector (DAD). The mobile phase was composed of B (methanol) and A (formic acid 1% v/v in H₂O) with a linear elution gradient: 0–20 min 20–80% B, 20–35 min 80% B, 35–45 min 20–80% B. The flow rate of the mobile phase was 1 mL/min and the injection volume was 10μL. The DAD detector was set up for monitoring between 200-400nm. The spectra were processed using an Xcalibur software (version 2.2).

The liquid chromatography–mass spectrometry (LC MS-MS) procedure was used to quantify DPS-2 in all samples obtained through ex vivo permeation study and differential tape stripping. In the present study, samples that contained DPS-2 were analyzed on a Thermo Scientific Accela 1000 UPLC system coupled to a Thermo Scientific TSQ Quantum Access MAX triple quadrupole mass spectrometer. The analysis was performed on a UHPLC chromatograph ACELLA (Thermo Fisher Scientific Inc., Madison, WI, USA), coupled to a triple quadrupole mass spectrometer TSQ Quantum Access MAX (Thermo Fisher Scientific Inc., Madison, WI, USA) with a heated electrospray ionization (HESI) interface. The column was a Zorbax Eclipse XDB C18 (150 mm × 4.6 mm, 5 µm particle size). The mobile phase was acetonitrile/0.1% formic acid = 60:40 (v/v), the flow rate was 0.5 mL min⁻¹, the column temperature was set to 30 °C, and the injection volume was 10 µL. DPS-2 was detected and quantified in positive HESI mode (m/z = 504.4).