Observations on the Changing Shape of the Ice Mass and the Determination of the Sublimation End Point in Freeze-Drying: An Application for Through-Vial Impedance Spectroscopy (TVIS)

Models for ice sublimation from a freeze-drying vial rely on the assumption of a planar ice interface up to ~25% loss of ice mass (which is difficult to qualify) whereas single-vial determinations of the sublimation endpoint (by temperature sensors) are based on the point when the observed temperatu...

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Autores principales:	Bhaskar Pandya, Geoff Smith, Irina Ermolina, Evgeny Polygalov
Formato:	article
Lenguaje:	EN
Publicado:	MDPI AG 2021
Materias:	freeze-drying primary drying endpoint thermocouple single-vial process analytical technology Pharmacy and materia medica RS1-441
Acceso en línea:	https://doaj.org/article/334a9891507a4d87abd29836de8879d7
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spelling	oai:doaj.org-article:334a9891507a4d87abd29836de8879d72021-11-25T18:41:05ZObservations on the Changing Shape of the Ice Mass and the Determination of the Sublimation End Point in Freeze-Drying: An Application for Through-Vial Impedance Spectroscopy (TVIS)10.3390/pharmaceutics131118351999-4923https://doaj.org/article/334a9891507a4d87abd29836de8879d72021-11-01T00:00:00Zhttps://www.mdpi.com/1999-4923/13/11/1835https://doaj.org/toc/1999-4923Models for ice sublimation from a freeze-drying vial rely on the assumption of a planar ice interface up to ~25% loss of ice mass (which is difficult to qualify) whereas single-vial determinations of the sublimation endpoint (by temperature sensors) are based on the point when the observed temperature reaches a plateau, which cannot differentiate between sublimation and desorption-drying. In this work, the real part capacitance of TVIS vial(s) containing frozen water (during sublimation drying) was measured at 100 kHz. This parameter <inline-formula><math display="inline"><semantics><mrow><msup><mi>C</mi><mo>′</mo></msup><mrow><mo>(</mo><mrow><mn>100</mn><mrow><mtext> </mtext><mi>kHz</mi></mrow></mrow><mo>)</mo></mrow></mrow></semantics></math></inline-formula> was shown to be highly sensitive to the shape and volume of the ice mass and is therefore a useful parameter for monitoring ice sublimation. By placing a digital camera in front of an isolated TVIS vial containing ice, it was possible to relate the changes in the shape of the ice mass with the changes in the trajectory of the time profile of <inline-formula><math display="inline"><semantics><mrow><msup><mi>C</mi><mo>′</mo></msup><mrow><mo>(</mo><mrow><mn>100</mn><mrow><mtext> </mtext><mi>kHz</mi></mrow></mrow><mo>)</mo></mrow></mrow></semantics></math></inline-formula> and determine the point of deviation from a planar ice interface and ultimately determine the point when the last vestiges of ice disappear. Thereafter, the same characteristics of the <inline-formula><math display="inline"><semantics><mrow><msup><mi>C</mi><mo>′</mo></msup><mrow><mo>(</mo><mrow><mn>100</mn><mrow><mtext> </mtext><mi>kHz</mi></mrow></mrow><mo>)</mo></mrow></mrow></semantics></math></inline-formula> time-profile were identified for those TVIS vials located out of sight of the camera in a separate full-shelf lyo study, thereby obviating the need for photographic examination.Bhaskar PandyaGeoff SmithIrina ErmolinaEvgeny PolygalovMDPI AGarticlefreeze-dryingprimary drying endpointthermocouplesingle-vialprocess analytical technologyPharmacy and materia medicaRS1-441ENPharmaceutics, Vol 13, Iss 1835, p 1835 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	freeze-drying primary drying endpoint thermocouple single-vial process analytical technology Pharmacy and materia medica RS1-441
spellingShingle	freeze-drying primary drying endpoint thermocouple single-vial process analytical technology Pharmacy and materia medica RS1-441 Bhaskar Pandya Geoff Smith Irina Ermolina Evgeny Polygalov Observations on the Changing Shape of the Ice Mass and the Determination of the Sublimation End Point in Freeze-Drying: An Application for Through-Vial Impedance Spectroscopy (TVIS)
description	Models for ice sublimation from a freeze-drying vial rely on the assumption of a planar ice interface up to ~25% loss of ice mass (which is difficult to qualify) whereas single-vial determinations of the sublimation endpoint (by temperature sensors) are based on the point when the observed temperature reaches a plateau, which cannot differentiate between sublimation and desorption-drying. In this work, the real part capacitance of TVIS vial(s) containing frozen water (during sublimation drying) was measured at 100 kHz. This parameter <inline-formula><math display="inline"><semantics><mrow><msup><mi>C</mi><mo>′</mo></msup><mrow><mo>(</mo><mrow><mn>100</mn><mrow><mtext> </mtext><mi>kHz</mi></mrow></mrow><mo>)</mo></mrow></mrow></semantics></math></inline-formula> was shown to be highly sensitive to the shape and volume of the ice mass and is therefore a useful parameter for monitoring ice sublimation. By placing a digital camera in front of an isolated TVIS vial containing ice, it was possible to relate the changes in the shape of the ice mass with the changes in the trajectory of the time profile of <inline-formula><math display="inline"><semantics><mrow><msup><mi>C</mi><mo>′</mo></msup><mrow><mo>(</mo><mrow><mn>100</mn><mrow><mtext> </mtext><mi>kHz</mi></mrow></mrow><mo>)</mo></mrow></mrow></semantics></math></inline-formula> and determine the point of deviation from a planar ice interface and ultimately determine the point when the last vestiges of ice disappear. Thereafter, the same characteristics of the <inline-formula><math display="inline"><semantics><mrow><msup><mi>C</mi><mo>′</mo></msup><mrow><mo>(</mo><mrow><mn>100</mn><mrow><mtext> </mtext><mi>kHz</mi></mrow></mrow><mo>)</mo></mrow></mrow></semantics></math></inline-formula> time-profile were identified for those TVIS vials located out of sight of the camera in a separate full-shelf lyo study, thereby obviating the need for photographic examination.
format	article
author	Bhaskar Pandya Geoff Smith Irina Ermolina Evgeny Polygalov
author_facet	Bhaskar Pandya Geoff Smith Irina Ermolina Evgeny Polygalov
author_sort	Bhaskar Pandya
title	Observations on the Changing Shape of the Ice Mass and the Determination of the Sublimation End Point in Freeze-Drying: An Application for Through-Vial Impedance Spectroscopy (TVIS)
title_short	Observations on the Changing Shape of the Ice Mass and the Determination of the Sublimation End Point in Freeze-Drying: An Application for Through-Vial Impedance Spectroscopy (TVIS)
title_full	Observations on the Changing Shape of the Ice Mass and the Determination of the Sublimation End Point in Freeze-Drying: An Application for Through-Vial Impedance Spectroscopy (TVIS)
title_fullStr	Observations on the Changing Shape of the Ice Mass and the Determination of the Sublimation End Point in Freeze-Drying: An Application for Through-Vial Impedance Spectroscopy (TVIS)
title_full_unstemmed	Observations on the Changing Shape of the Ice Mass and the Determination of the Sublimation End Point in Freeze-Drying: An Application for Through-Vial Impedance Spectroscopy (TVIS)
title_sort	observations on the changing shape of the ice mass and the determination of the sublimation end point in freeze-drying: an application for through-vial impedance spectroscopy (tvis)
publisher	MDPI AG
publishDate	2021
url	https://doaj.org/article/334a9891507a4d87abd29836de8879d7
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Observations on the Changing Shape of the Ice Mass and the Determination of the Sublimation End Point in Freeze-Drying: An Application for Through-Vial Impedance Spectroscopy (TVIS)

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