15 research outputs found
Quantifying crystal form content in physical mixtures of (±)-tartaric acid and (+)-tartaric acid using near infrared reflectance spectroscopy
The objective of this study was to use diffuse reflectance near infrared spectroscopy (NIRS) to determine racemic compound content in physical mixtures composed primarily of the enantiomorph and to assess the error, instrument reproducibility and limits of detection (LOD) and quantification (LOQ) of the method. Physical mixtures ranging from 0 to 25% (±)-tartaric acid in (+)-tartaric acid were prepared and spectra of the powder samples contained in glass vials were obtained using a Foss NIRSystems Model 5000 monochrometer equipped with a Rapid Content Analyzer scanning from 1100 to 2500 nm. A calibration curve was constructed by plotting (±)-tartaric acid weight percent against the 2nd derivative values of log (1/R) vs λ at a single wavelength, normalized with a denominator wavelength (1480 nm/1280 nm). Excellent linearity was observed (R2=0.9999). The standard error of calibration (SEC) was 0.07 and the standard error of prediction (SEP) for the validation set was 0.11. Instrument and method errors for samples in the 2% composition range ((±)-tartaric acid in (+)-tartaric acid) were less than 1% RSD and 3% RSD, respectively. The practical LOD and LOQ were 0.1% and 0.5%, respectively, and comparable to the calculated LOD and LOQ. These studies show that NIRS can be used as a rapid and sensitive quantitative method for determining racemate content in the presence of the enatiomerically pure crystal in the solid-state
Effect of vacuum drying on protein-mannitol interactions: The physical state of mannitol and protein structure in the dried state
The purpose of the present studies was to systematically investigate protein-mannitol interactions using vacuum drying, to obtain a better understanding of the effect of protein/mannitol wt/wt ratios on the physical state of mannitol and protein secondary structure in the dried state. Solutions containing ÎČ-lactoglobulin (ÎČLg):mannitol (1â¶1â1â¶15 wt/wt) were vacuum dried at 5°C under 3000 mTorr of pressure. The physical state of mannitol was studied using x-ray powder physical state of mannitol was studied using x-ray powder diffractometry (XRPD), polarized light microscopy (PLM), Fourier-transform infrared (FTIR) spectroscopy, and modulated differential scanning calorimetry (MDSC). XRPD studies indicated that mannitol remained amorphous up to 1â¶5 wt/wt ÎČLg:mannitol ratio, whereas PLM showed the presence of crystals of mannitol in all dried samples except for the 1â¶1 wt/wt ÎČLg:mannitol dried sample. FITR studies indicated that a small proportion of crystalline mannitol was present along with the amorphous mannitol in dried samples at lower (less than 1â¶5 wt/wt) ÎČLg:mannitol ratios. The Tg of the dried 1â¶1 wt/wt ÎČLg:mannitol sample was observed at 33.4°C in MDSC studies, which indicated that at least a part of mannitol co-existed with protein in a single amorphous phase. Evaluation of the crystallization exotherms indicated that irrespective of the ÎČLg:protein wt/wt ratio in the initial sample, the protein to amorphous mannitol ratio was below 1â¶1 wt/wt in all dried samples. Second-derivative FTTR studies on dried ÎČLg and recombinant human interferon α-2a samples showed that mannitol affected protein secondary structure to a varying degree depending on the overall mannitol content in the dried sample and the type of protein