Abstract
In this study, coating thickness and uniformity of production-scale pharmaceutical tablets were investigated using near-infrared (NIR) and terahertz pulse imaging (TPI) spectroscopy. Two coating formulations were considered; samples for each coating formulation were obtained at 0, 1, 2, 3, 4, and 5% coating weight. NIR spectra were collected, and regressed with respect to batch percent weight gain. While standard errors of calibration (SEC) less than 0.5% were observed for both formulations, the calibrations were not specifically sensitive to coating thickness. An upper limit for NIR coating thickness analysis was estimated to be ∼4–6% weight gain for this system. The NIR calibrations were used as filters to choose subsets of samples for TPI, and as a secondary method for validation of TPI results. The features in TPS time-domain spectra result when an incident THz plane wave meets a refractive index interface, which may be converted to an absolute distance. Therefore, assuming that a discernible difference in refractive index between coating material and core exists, coating thickness can be determined non-destructively. Coating thickness measurements from TPI and NIR spectroscopy were compared to estimate the lower limit for quantitative TPI coating analysis; a lower limit of ∼35 mm was obtained for this system. Optical microscopy was employed on a subset of samples to validate absolute thickness values; reasonable correlations between the three methods were obtained. TPI was considered advantageous relative to the other methods, as similar results were obtained without the need for destructive sampling or empirical calibration development.
Similar content being viewed by others
References
Ansel HC, Allen LV Jr, Popovich NG. Capsules and tablets. Pharmaceutical dosage forms and drug delivery systems. 7th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 1999. p. 179–228.
Cogdill RP, Anderson CA, Delgado-Lopez M, Chisholm R, Bolton R, Herkert T, et al. Process analytical technology case study, part II: development and validation of quantitative for tablet API content and hardness. AAPS PharmSciTech 2005;6(2):273–83.
Cogdill RP, Anderson CA, Delgado-Lopez M, Molseed D, Chisholm R, Bolton R, et al. Process analytical technology case study, part I: feasibility studies for quantitative NIR method development. AAPS PharmSciTech 2005;6(2):262–72.
Cogdill RP, Anderson CA, Drennen JK. Process analytical technology case study, part III: calibration monitoring and transfer. AAPS PharmSciTech 2005;6(2):284–97.
FDA. PAT—a framework for innovative manufacturing and quality assurance; 2004.
Fitzgerald AJ, Cole BE, Taday PF. Nondestructive analysis of tablet coating thickness using terahertz pulsed imaging. J Pharm Sci 2004;94(1):177–83.
Mowery MD, Sing R, Kirsch JD, Razaghi A, Béchard S, Reed RA. Rapid at-line analysis of coating thickness and uniformity on tablets using laser induced breakdown spectroscopy. J Pharm Biomed Anal 2002;28:935–43.
Cogdill RP, Drennen JK. Near-infrared spectroscopy. In: Brittain HG, editor. Spectroscopy of pharmaceutical solids. New York, NY: Taylor & Francis Group; 2006. p. 313–412.
Taday PF. Applications of terahertz spectroscopy to pharmaceutical sciences. Philos Trans R Soc Lond A 2004;362:351–64.
Kirsch JD, Drennen JK. Determination of film-coated tablet parameters by near-infrared spectroscopy. J Pharm Biomed Anal 1995;13:1273–81.
Pérez-Ramos JD, Findlay WP, Peck GE, Morris KR. Quantitative analysis of film coating in a pan coater based on in-line sensor measurements. AAPS Pharm Sci Techol 2005;6(1):E127–36.
Beard MC, Turner GM, Schumuttenmaer CA. Terahertz spectroscopy. J Phys Chem B 2002;106:7146–59.
Hangyo M, Tani M, Nagashima T. Terahertz time-domain spectroscopy of solids: a review. Int J Infrared Millim Waves 2005;26(12):1661–90.
Lucarini V, Ino Y, Peiponen K-E, Kuwata-Gonokami M. Detection and correction of the misplacement error in terahertz spectroscopy by application of singly subtractive Kramers–Kronig relations. Phys Rev, B 2005;72(12):125107(125106).
Cogdill RP, Short SM, Forcht RN, Shi Z, Shen YC, Taday PF, et al. An efficient method development strategy for quantitative chemical imaging via terahertz pulse spectroscopy. J Pharm Innovation 2006;1(1):63–75.
Shen YC, Lo T, Taday PF, Cole BE, Tribe WR, Kemp MC. Detection and identification of explosives using terahertz pulsed spectroscopic imaging. Appl Phys Lett 2005;86(241116):24–31.
Shen YC, Taday PF, Newnham DA, Kemp MC, Pepper M. 3D Chemical mapping using terahertz pulse imaging. Proc SPIE 2005;5727:24–31.
Strachan CJ, Rades T, Newnham DA, Gordon KC, Pepper M, Taday PF. Using terahertz pulsed spectroscopy to study crystallinity of pharmaceutical materials. Chem Phys Lett 2004;290:20–4.
Neil GR, Carr GL, Gubeli JF III, Jordan K, Martin MC, McKinney WR, et al. Production of high power femtosecond terahertz radiation. Nucl Instrum Methods Phys Res A 2003;507:537–40.
Cole BE, Woodward RM, Crawley D, Wallace VP, Arnone DD, Pepper M. Terahertz imaging and spectroscopy of human skin, in-vivo. Proc SPIE 2001;4276(1–10):1–10.
Woodward RM, Cole BE, Wallace VP, Pye RJ, Arnone DD, Linfield EH, et al. Terahertz pulse imaging in reflection geometry of human skin cancer and skin tissue. Phys Med Biol 2002;47:3853–63.
Acknowledgements
The authors would like to thank the Duquesne University department of biology for use of their microscopy facilities and equipment.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Cogdill, R.P., Forcht, R.N., Shen, Y. et al. Comparison of Terahertz Pulse Imaging and Near-Infrared Spectroscopy for Rapid, Non-Destructive Analysis of Tablet Coating Thickness and Uniformity. J Pharm Innov 2, 29–36 (2007). https://doi.org/10.1007/s12247-007-9004-0
Published:
Issue Date:
DOI: https://doi.org/10.1007/s12247-007-9004-0