title: Quantification of glycine crystallinity by near-infrared (NIR) spectroscopy.
abstract: The object of this investigation was to use near-infrared (NIR) spectroscopy for quantification of glycine crystallinity. Glycine samples, with different degrees of crystallinity, were obtained by physically mixing different proportions of crystalline beta-glycine with amorphous glycine. NIR spectra were obtained, directly from samples in glass vials, over the wavelength range of 1100-2500 nm. A partial least squares (PLS) model was developed to correlate the NIR spectral changes with the degree of crystallinity. Using this model, a standard error of calibration (SEC) of 2.1% was obtained with an r(2) value of 0.996. Cross validation was used to test the precision of the quantitative model, resulting in a standard error of prediction (SEP) of 3.2%. These results indicate that NIR spectroscopy is well suited to the measurement of glycine crystallinity in lyophilized products. Employing the PLS model, the crystallinity of glycine in freeze-dried sucrose-glycine mixtures was evaluated. At a sucrose to glycine ratio >4, glycine crystallization during lyophilization was inhibited. Conversely, at ratios < or =0.67, glycine remained substantially crystalline. At intermediate compositions, the glycine was partially crystalline.
authors.affiliation: Center for Pharmaceutical Biotechnology, University of Colorado Health Sciences Center, Denver, CO 80262, USA.
authors.forename: Shu Jun
authors.initials: SJ
authors.lastname: Bai
authors.forename: Meena
authors.initials: M
authors.lastname: Rani
authors.forename: Raj
authors.initials: R
authors.lastname: Suryanarayanan
authors.forename: John F
authors.initials: JF
authors.lastname: Carpenter
authors.forename: Rajiv
authors.initials: R
authors.lastname: Nayar
authors.forename: Mark C
authors.initials: MC
authors.lastname: Manning
mesh_terms: D003460:Crystallization; D005998:Glycine / Q000737:chemistry*; D019265:Spectroscopy, Near-Infrared; D013395:Sucrose; D014961:X-Ray Diffraction
chemical_list: D013395:Sucrose; D005998:Glycine