Quantification of glycine crystallinity by near-infrared (NIR) spectroscopy.
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.
Bai
Shu Jun
SJ
Center for Pharmaceutical Biotechnology, University of Colorado Health Sciences Center, Denver, CO 80262, USA.
Rani
Meena
M
Suryanarayanan
Raj
R
Carpenter
John F
JF
Nayar
Rajiv
R
Manning
Mark C
MC
D003460:Crystallization; D005998:Glycine / Q000737:chemistry*; D019265:Spectroscopy, Near-Infrared; D013395:Sucrose; D014961:X-Ray Diffraction
D013395:Sucrose; D005998:Glycine