A validated reverse-phase isocratic Shimadzu HPLC system (Shimadzu, Kyoto, Japan) furnished with LC-10 AT solvent delivery unit, SPD-10 AVP UV/Vis detector (sensitivity of 0.005 absorbance units full scale, AUFS) was used to analyze DTX concentration in the samples. The mobile phase was composed of acetonitrile and double distilled water in a volume ratio of 75:25 and was pumped through the Phenomenex® Luna C18 column (5 µm, 4.6 × 250 mm; Phenomenex, Torrence, California) maintained at 25oC at a flow rate of 1 mL/min. 20 mL of sample was injected through the Rheodyne injector and analyzed at a λmax of 227 nm.
The saturation solubility of DTX in various vehicles (oils, surfactants, cosurfactants) was estimated using the previously developed shake flask method (Zhou 2007). Briefly an excess amount of DTX (approximately 200 mg) was mixed with 1 gm of chosen vehicles in 5 ml clean glass vials with ...view middle of the document...
J. Pharm. Sci. 96:3052–3071; 2007.
Powder X-ray diffraction studies
Powder X-ray diffraction pattern of the samples was recorded at ambient room conditions using
X-ray diffractometer (X’Pert PRO Panalytical, Eindhoven, Netherlands) equipped with real time multistrip X’Celerator detector, 2θ compensating slit and Cu Kα source (1.54 Å) operating at a generator power of 40 kV and current 40 mA. Powder sample was loaded in the sample holder as a thin layer and scanned in a step scan mode over an angular range from 4-50° 2θ (step size -0.02◦ and scan rate of 1 s/step).
Differential scanning calorimetry (DSC)
Thermal behavior of the samples was determined from thermograms developed using differential scanning calorimetry (Mettler DSC 823e, Mettler-Toledo, Germany) calibrated with indium (calibration standard, purity > 99.9%). Accurately weighed sample (4 mg) was placed in a flat bottomed standard aluminum pan and scanned at a scanning speed of 10°C/min from 20○C to 300○C under a nitrogen gas flow of 80 mL/min.
Scanning electron microscopy
The surface morphological observation of the samples was performed using scanning electron microscope (SEM, S-4100, Hitachi Ltd., Tokyo, Japan). Each sample was mounted on a sterilized metal stub with double sided adhesive carbon tape by light dusting and gold coated in vacuum (3-5 nm/min; 100 s; 30 W; 4 Psi) to make them electrically conductive using ion sputter (E-1010, Hitachi Ltd., Tokyo, Japan). The SEM micrographs of samples were captured at an accelerating voltage of 15 kV.
Fourier transform infrared spectroscopy (FTIR)
FTIR spectrum of the samples was recorded by KBr disc method using Perkin Elmer FT-IR Spectrometer (Paragon 1000, PerkinElmer, Waltham, Massachusetts, USA) to illustrate the promising interactions among the components used in the formulation. Powder sample (4 mg) and IR grade dry potassium bromide (KBr; 200 mg) were mixed gently in a glass mortar, compacted to form disk by applying a force of 5.5 metric tons using hydraulic press. The corresponding disks were scanned over the wave number range of 4000–400 cm-1 at a scanning speed of 4 scans /s with a resolution of 1 cm-1 for each spectrum.