Synergi 4 m polar rp column

NP were dissolved in acetonitrile and drug content was estimated through HPLC-UV for PTX and HPLC-MS for BIBF. PTX content in the NP was quantified using HPLC-UV (2690 Alliance separation module coupled with 2487 dual λ absorbance detector, Waters, Milford, MA). Reverse phase 5 µm C-18 column, 100 A°, 4.5 × 250 mm (Waters) was utilized in the assay and isocratic elution with a mobile phase of acetonitrile (Fisher Scientific): water (60:40, v/v) at a flow rate of 1 mL/min was used. The detection wavelength was set at 227 nm and the injection volume was 100 µL. BIBF content was determined using HPLC-Mass (Shimadzu Model 2010A liquid chromatograph and mass spectrometer, Shimadzu, Columbia, MD) using a LC-10AD VP Solvent Delivery system. Synergi 4 µm Polar-RP column, 80 A°, 2 × 150 mm (Phenomenex Inc, Torrance, California) was used. Isocratic elution was utilized with a mobile phase composed of water + 0.1% formic acid (Fisher Scientific): acetonitrile + 0.1% formic acid (50:50, v/v), at a flow rate of 0.2 mL/min. Electrospray ionization was used, m/z ratio of 540.5 was utilized, and 25 µL was injected.
Drug loadings and encapsulation efficiencies were calculated from the following formulas.
$$\text{Drug loading }\left(\frac{\mathrm{\mu }\mathrm{g}\text{ of drug}}{\text{mg of NP}}\right)=\frac{\text{Amount of PTX in NP }(\mathrm{\mu }\mathrm{g})}{\text{Total weight of NP }(\text{mg})}$$
$$\text{Encapsulation efficiency }(\%)=\frac{\text{Amount of PTX in NP }(\text{mg})}{\text{Initial amount of PTX }(\text{mg})}\times 100$$