**2.9 Analysis of optimized LSCs**

Based on the results of evaluation tests, one LSC formulation was optimized from the prepared batch and selected for further analytical characterization. This optimized drug loaded LSC was subjected to FTIR and DSC studies to determine presence of any possible interaction between drug and excipients. SEM studies were also performed to study surface morphology and XRD studies for determining the solid-state characterization.

*Development of Liquisolid Compacts: An Approach for Dissolution Enhancement of Poorly… DOI: http://dx.doi.org/10.5772/intechopen.108706*

#### *2.9.1 Fourier-transform infrared spectroscopy (FTIR)*

Drug-excipient interactions play crucial role in release of drug from the formulation and hence the compatibility studies were performed using FT-IR spectrophotometer. IR spectrum was determined for samples by FTIR-8400S spectrophotometer (Shimadzu, Japan) using KBr pellet method. In this method, 100 mg of dry KBr IR powder is carefully mixed with 5 mg of sample (drug or formulation). It is further compressed to transparent discs at a pressure of 12,000 psi under vacuum for about 3 min. The obtained disc was mounted in holder and the sample was scanned over a wave range of 4000 to 400 cm�<sup>1</sup> , at a resolution of 4 cm�<sup>1</sup> using FTIR spectrophotometer. FTIR was executed for both the pure drug and LS powders [24].

#### *2.9.2 Differential scanning calorimetry (DSC)*

DSC Thermograms of pure drug and the optimized LSC formulation for drug were recorded using the calibrated Shimadzu DSC-60 (Shimadzu, Kyoto, Japan) [19]. Samples of weight around 3 to 5 mg were weighed. They were placed in aluminum pans whose lids were crimped taking Shimadzu crimper. The samples were investigated over a scanning rate of 10°C/min to determine their thermal behavior, covering a wide temperature range of 30–200°C under nitrogen atmosphere. The DSC was calibrated using indium standard [25].

#### *2.9.3 Powder X-ray diffraction (PXRD)*

The crystalline nature pure drug as well as samples can be determined by Philips Analytical XRD using copper target. At room temperature, the operating voltage was 40 kV and current used was around 55 mA [26].

#### *2.9.4 Scanning electron microscopy (SEM)*

The surface morphology characteristics of pure drug as well as the drug–carrier systems or formulations were assessed using scanning electron microscopy. The external surface morphology of the LSCs were studied using a scanning electron microscope (Hitachi TM 1000, Tokyo, Japan). The samples were first adhered to aluminum stubs, gold-coated sputter with double sided conductive tape of 12 mm diameter, and examined in the scanning microscope [27].

#### **2.10 Stability studies**

Stability can be explained as the extent to which a product will retain its specified limits throughout the shelf life. The accelerated stability studies for optimized LSC formulation were performed according to ICH guidelines at temperature of 40 � 2°C and relative humidity (RH) of 75% RH � 5% for duration of 6 months in a stability chamber. USP Type I flint vials are used to place the selected optimized formulations. They are then hermetically closed using bromo butyl rubber plugs and further sealed with aluminum caps. The samples were taken at specific time periods and evaluated for post compression tests. These results of aged samples were compared with fresh (initial) samples kept at room temperature and similarity factor was determined [28].
