Invia reflex

Confocal Raman microspectroscopy (CRM) provides noninvasive and nondestructive microspectroscopic component analysis of DPI formulations. Using similar conditions previously reported^{20 (link),45 (link),49 (link)–51 (link)}, Raman spectra were obtained at 514 nm laser excitation using Renishaw InVia Reflex using a 20 × magnification objective on a Leica DM2700 optical microscope. Raman spectral map was obtained with the stage moved in increments of 20 × 20 µm in each axis. Each map point was acquired 1 accumulation using 2 s of detector exposure time per accumulation.

Raman spectroscopy studies were performed using a Renishaw InVia Reflex dispersive spectrometer with Leica microscope (Renishaw, Wotton under Edge, UK). An excitation source of λ = 785 nm, 300 mW was applied with spectral resolution 1 cm⁻¹. Laser power was dependent on the sample and varied from 1% to 10% of the power. The spectra were accumulated within 10–300 s integration time. Test conditions T = 22 ± 2 °C, RH = 40 ± 2%. The analysis by Raman technique was carried out in a closed microscope chamber of the spectroscope with samples being placed on the microscope plate. Samples were positioned in the laser light focus using a microscope (magnification 50×) with CCD camera. The recording of spectra was carried out by Renishaw WiRE™ software (v.3.2, Wotton under Edge, UK). All Spectra processing was done with the use of Origin software (OriginLab, v.8.0, Northampton, MA, USA).

Raman spectra were obtained using a Renishaw InVia Reflex spectrometer coupled with a Leica optical microscope. The instrument was equipped with a double-edge filter to eliminate the Rayleigh scattering and with a CCD camera working at a temperature of 220 K with a 1024 × 246 pixel array. The spectral resolution achieved with the use of gratings of 2400 grooves/mm was 3 cm⁻¹. The wavenumber accuracy in a vacuum was better than 0.8 cm⁻¹. All spectra were recorded in the 300–1100 cm⁻¹ range with an argon ion laser source emitting a 514.53 nm excitation wavelength. Inelastic spectra were collected in the backscattering mode via the confocal optical microscope. A ×50 magnification objective allowed a precise area analysis with a focused laser power of 1 mW/µm². The probed area was around 4 µm². The powder sample was deposited onto a glass pure silica slide. The powder surface was flattened with a flat spatula to have a well-defined focal distance. Measurements were performed on several points of the sample to ensure homogeneity and the focused power of the laser beam was checked for each wavelength to avoid any transformation or heating of the sample.