In situ monitoring of solid‐state transition of p‐aminobenzoic acid polymorphs using Raman spectroscopy

Abstract

The purpose of this study is to investigate the mechanism of solid-state polymorphic transition of p-aminobenzoic acid (PABA) using in situ Raman spectroscopy measurement. The polymorphic transition experiments were conducted on a micro quartz vessel mounted on a microscope, hot and cold stage, under isothermal conditions. The temperature was precisely controlled by a standalone temperature controller equipped with liquid nitrogen cooling system. The Raman spectroscopy probe was positioned on the surface of the solid sample in the micro vessel. The polymorphic transition progression was in situ monitored and recorded by Raman spectroscopy. Based on the polymorphic transition rate resulted from the quantitative analysis of Raman spectra, the mechanism of solid-state polymorphic transition of PABA was examined by various empirical kinetic models. An Arrhenius analysis was also performed to calculate activation energies from 134.7 kJ mol −1 to 137.7 kJ mol −1 for the transition. The results demonstrated that in situ Raman spectroscopy is a valuable and accurate technique to probe polymorphic transition process.

Structural Characterization of Co-Crystals of Chlordiazepoxide with p-Aminobenzoic Acid and Lorazepam with Nicotinamide by DSC, X-ray Diffraction, FTIR and Raman Spectroscopy

“…Raman bands at 1181.0 and 1133.0 cm −1 found in the chlordiazepoxide physical mixture spectrum disappeared in the co-crystal spectra, while another at 1515.9 cm −1 is shifted to 1521 cm −1 . Moreover, the band at 1287cm −1 in the mixture spectrum assigned to the hydroxyl stretching of p -aminobenzoic acid [ 46 ] changes position slightly to ~1284 cm −1 and a new strong band at 1255 cm −1 , near the hydroxyl band, is created in the co-crystal spectra.…”

Polymorphism in p-aminobenzoic acid

“…In 2008 Yang et al 58 confirmed this result and used Raman spectroscopy to measure the rate of the solid state transformation from β to α at temperatures between 78 and 100°C. They observed no intermediate forms and estimated the activation energy to be 136 kJmol -1 .…”

Recent advances in linear and nonlinear Raman spectroscopy. Part IV

“…Yang et al [243] investigated the mechanism of solid-state polymorphic transition of p-aminobenzoic acid (PABA) using in situ Raman spectroscopy. High-resolution micro-Brillouin scattering and heat capacity studies of polar bis(guanidinium)zirconium bis(nitrilotriacetate) hydrate were performed by Maczka et al [244] in the temperature range 230-305 K.…”

“…Phase transitions were described by Vikram et al 242 involving the dynamics and mechanism of the crystal II smectic G phase transition for erepthal‐bis‐heptylaniline by a temperature‐dependent micro‐Raman study and DFT calculations. Yang et al 243 investigated the mechanism of solid‐state polymorphic transition of p ‐aminobenzoic acid (PABA) using in situ Raman spectroscopy. High‐resolution micro‐Brillouin scattering and heat capacity studies of polar bis(guanidinium)zirconium bis(nitrilotriacetate) hydrate were performed by Maczka et al 244 in the temperature range 230–305 K.…”