title: Non-contact weight measurement of flat-faced pharmaceutical tablets using terahertz transmission pulse delay measurements.
abstract: By measuring the time delay of a terahertz pulse traversing a tablet, and hence its effective refractive index, it is possible to non-invasively and non-destructively detect the weight of tablets made of microcrystalline cellulose (MCC). Two sets of MCC tablets were used in the study: Set A (training set) consisted of 13 tablets with nominally constant height but varying porosities, whereas Set B (test set) comprised of 21 tablets with nominally constant porosity but different heights. A linear correlation between the estimated absolute weight based on the terahertz measurement and the measured weight of both sets of MCC tablets was found. In addition, it was possible to estimate the height of the tablets by utilizing the estimated absolute weight and calculating the relative change of height of each tablet with respect to an ideal tablet. A good agreement between the experimental and the calculated results was found highlighting the potential of this technique for in-line sensing of the weight, porosity and the relative change in height of the tablets compared to a reference/ideal tablet. In this context, we propose a quantitative quality control method to assess the deviations in porosity of tablets immediately after compaction.
authors.affiliation: Institute of Photonics, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland; Department of Chemical Engineering and Biotechnology, University of Cambridge, Pembroke Street, Cambridge CB2 3RA, United Kingdom. Electronic address: prince.bawuah@uef.fi.
authors.forename: Prince
authors.initials: P
authors.lastname: Bawuah
authors.affiliation: Institute of Photonics, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland.
authors.forename: Pertti
authors.initials: P
authors.lastname: Silfsten
authors.affiliation: School of Pharmacy, Promis Centre, University of Eastern Finland, P.O. Box 1617, FI-70211, Finland.
authors.forename: Tuomas
authors.initials: T
authors.lastname: Ervasti
authors.affiliation: School of Pharmacy, Promis Centre, University of Eastern Finland, P.O. Box 1617, FI-70211, Finland.
authors.forename: Jarkko
authors.initials: J
authors.lastname: Ketolainen
authors.affiliation: Department of Chemical Engineering and Biotechnology, University of Cambridge, Pembroke Street, Cambridge CB2 3RA, United Kingdom.
authors.forename: J Axel
authors.initials: JA
authors.lastname: Zeitler
authors.affiliation: Institute of Photonics, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland.
authors.forename: Kai-Erik
authors.initials: KE
authors.lastname: Peiponen
mesh_terms: D002482:Cellulose / Q000737:chemistry*; D002626:Chemistry, Pharmaceutical / Q000379:methods; D005079:Excipients / Q000737:chemistry*; D016062:Porosity; D011786:Quality Control; D012031:Refractometry; D013499:Surface Properties; D013607:Tablets; D013678:Technology, Pharmaceutical / Q000379:methods*; D055053:Terahertz Radiation; D055068:Terahertz Spectroscopy / Q000379:methods*
chemical_list: D005079:Excipients; D013607:Tablets; D002482:Cellulose; C109691:microcrystalline cellulose
keywords: Compaction; Effective refractive index; High throughput technologies; Microcrystalline cellulose (MCC); Process analytical technology; Simulations; Tablet height; Tablet weight; Tablets; Terahertz spectroscopy