Iraffinity is fourier transform infrared spectrophotometer

FT-IR spectra were collected on an IRAffinity-IS Fourier-Transform Infrared Spectrophotometer (Shimadzu, Kyoto, Japan) instrument in the range of 400–4000 cm⁻¹, with a resolution of 4.0 cm⁻¹ and 40 scans.
First, 1 mg of lyophilized PLGA NPs (ETO-NPs, CBD-NPs, and ETO+CBD-NPs) was micronized and mixed with 300 mg of KBr (Sigma Aldrich, Saint Louis, MO, USA) to produce tablets (1.3 cm × 0.1 cm). The reference spectra were obtained by using the same tableting method, by mixing 1 mg of ETO, CBD, or blank-NPs with 300 mg of KBr. The obtained spectra of the loaded PLGA NPs were compared with the reference spectra, and the purity index (PI) indicating the degree of matching between the two spectra was determined for each pair. PI is expressed as the least-squares-fit coefficient calculated for every intensity pair of the two spectra being compared, and it was calculated using the following formula: $$PI=\frac{\sum _i^n(s_i-\overline{s})\times (r_i-\overline{r})}{\sqrt{\sum _i^n{(s_i-\overline{s})}^2\times \sum _i^n{(r-\overline{r})}^2}}$$
where s_i and r_i are the respective intensities for the same horizontal coordinate value, and n is the number of data points; $\overline{\mathrm{s}}$ and $\overline{r}$ are the average intensities of each spectrum.
The purity value is between 0 and 1, where 0 indicates a lack of identity between the two spectra, and 1 indicates that the two spectra are identical.

The precipitate was filtered and dried. Then, 1 mg of precipitate (tested sample) was micronized and mixed with 300 mg of KBr to produce tablets (1.3 cm × 0.1 cm). The reference spectrum was obtained by using the same tableting method by mixing 1 mg of CF (Sigma Aldrich, Saint Louis, MO, USA) with 300 mg of KBr. FT-IR spectra were collected on an IRAffinity-IS Fourier Transform Infrared Spectrophotometer (Shimadzu, Kyoto, Japan) instrument in the range of 400–4000 cm^−1, with a resolution of 4.0 cm⁻¹ and 40 scans. The identity of CF was confirmed by comparing the spectrum of precipitate with the spectrum of the reference sample and by calculating the purity factor. Purity (P) is a factor that indicates the degree of matching between two spectra. This factor is given by the least-squares-fit coefficient that is calculated for every intensity pair of the two spectra being compared. P factor can be calculated by using the following formula: $P=\frac{{\sum }_i^n\left(s_i-\overline{s}\right)\times (r_i-\overline{r})}{\sqrt{{\sum }_i^n{\left(s_i-\overline{s}\right)}^2\times {\sum }_i^n{\left(r-\overline{r}\right)}^2}},$
where s_i and r_i are the respective intensities for the same horizontal coordinate value, and n is the number of data points; $\overline{s}$ and $\overline{r}$ are the average intensities of each spectrum.
The purity value is between 0 and 1, where 0 indicates no identity between the two spectra, and 1 indicates that the two spectra are identical.