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Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - Measurement of the inter-tablet coating uniformity of a pharmaceutical pan coating process with combined terahertz and optical coherence tomography in-line sensing
AU - Lin, Hungyen
AU - Dong, Yue
AU - Markl, Daniel
AU - Williams, Bryan M.
AU - Zheng, Yalin
AU - Shen, Yaochun
AU - Zeitler, J. Axel
PY - 2017/4
Y1 - 2017/4
N2 - We present in-line coating thickness measurements acquired simultaneously using two independent sensing modalities: terahertz pulsed imaging (TPI) and optical coherence tomography (OCT). Both techniques are sufficiently fast to resolve the coating thickness of individual pharmaceutical tablets in-situ during the film coating operation and both techniques are direct structural imaging techniques that do not require multivariate calibration. The TPI sensor is suitable to measure coatings greater than 50 μm and can penetrate through thick coatings even in the presence of pigments over a wide range of excipients. Due to the long wavelength, terahertz radiation is not affected by scattering from dust within the coater. In contrast, OCT can resolve coating layers as thin as 20 μm and is capable of measuring the intra-tablet coating uniformity as well as the inter-tablet coating thickness distribution within the coating pan. However, the OCT technique is less robust when it comes to the compatibility with excipients, dust and potentially the maximum coating thickness that can be resolved. Using a custom built laboratory scale coating unit, the coating thickness measurements were acquired independently by the TPI and OCT sensors throughout a film coating operation. Results of the in-line TPI and OCT measurements were compared against one another and validated with off-line TPI and weight gain measurements. Compared to other process analytical technology (PAT) sensors, such as near-infrared and Raman spectroscopy, the TPI/OCT sensors can resolve the inter-tablet thickness distribution based on sampling a significant fraction of the tablet populations in the process. By combining two complementary sensing modalities it was possible to seamlessly monitor the coating process over the range of film thickness from 20 μm to greater than 250 μm.
AB - We present in-line coating thickness measurements acquired simultaneously using two independent sensing modalities: terahertz pulsed imaging (TPI) and optical coherence tomography (OCT). Both techniques are sufficiently fast to resolve the coating thickness of individual pharmaceutical tablets in-situ during the film coating operation and both techniques are direct structural imaging techniques that do not require multivariate calibration. The TPI sensor is suitable to measure coatings greater than 50 μm and can penetrate through thick coatings even in the presence of pigments over a wide range of excipients. Due to the long wavelength, terahertz radiation is not affected by scattering from dust within the coater. In contrast, OCT can resolve coating layers as thin as 20 μm and is capable of measuring the intra-tablet coating uniformity as well as the inter-tablet coating thickness distribution within the coating pan. However, the OCT technique is less robust when it comes to the compatibility with excipients, dust and potentially the maximum coating thickness that can be resolved. Using a custom built laboratory scale coating unit, the coating thickness measurements were acquired independently by the TPI and OCT sensors throughout a film coating operation. Results of the in-line TPI and OCT measurements were compared against one another and validated with off-line TPI and weight gain measurements. Compared to other process analytical technology (PAT) sensors, such as near-infrared and Raman spectroscopy, the TPI/OCT sensors can resolve the inter-tablet thickness distribution based on sampling a significant fraction of the tablet populations in the process. By combining two complementary sensing modalities it was possible to seamlessly monitor the coating process over the range of film thickness from 20 μm to greater than 250 μm.
KW - terahertz sensing
KW - optical coherence tomography
KW - pharmaceutical film coating
KW - coating thickness
KW - coating uniformity
KW - terahertz pulsed imaging
U2 - 10.1016/j.xphs.2016.12.012
DO - 10.1016/j.xphs.2016.12.012
M3 - Journal article
VL - 106
SP - 1075
EP - 1084
JO - Journal of Pharmaceutical Sciences
JF - Journal of Pharmaceutical Sciences
SN - 0022-3549
IS - 4
ER -