title: Rapid determination of vial heat transfer parameters using tunable diode laser absorption spectroscopy (TDLAS) in response to step-changes in pressure set-point during freeze-drying.
abstract: The purpose of this study was to perform a rapid determination of vial heat transfer parameters, that is, the contact parameter K(cs) and the separation distance l(v), using the sublimation rate profiles measured by tunable diode laser absorption spectroscopy (TDLAS). In this study, each size of vial was filled with pure water followed by a freeze-drying cycle using a LyoStar II dryer (FTS Systems) with step-changes of the chamber pressure set-point at to 25, 50, 100, 200, 300, and 400 mTorr. K(cs) was independently determined by nonlinear parameter estimation using the sublimation rates measured at the pressure set-point of 25 mTorr. After obtaining K(cs), the l(v) value for each vial size was determined by nonlinear parameter estimation using the pooled sublimation rate profiles obtained at 25 to 400 mTorr. The vial heat transfer coefficient K(v), as a function of the chamber pressure, was readily calculated, using the obtained K(cs) and l(v) values. It is interesting to note the significant difference in K(v) of two similar types of 10 mL Schott tubing vials, primary due to the geometry of the vial-bottom, as demonstrated by the images of the contact areas of the vial-bottom.
authors.affiliation: BioPharma Solutions, Baxter Healthcare Corporation, 927 South Curry Pike, Bloomington, Indiana 47403, USA. wei_kuu@baxter.com
authors.forename: Wei Y
authors.initials: WY
authors.lastname: Kuu
authors.forename: Steven L
authors.initials: SL
authors.lastname: Nail
authors.forename: Gregory
authors.initials: G
authors.lastname: Sacha
mesh_terms: D005612:Freeze Drying / Q000191:economics / Q000295:instrumentation* / Q000379:methods*; D054023:Lasers, Semiconductor; D008962:Models, Theoretical; D011312:Pressure; D012044:Regression Analysis; D013057:Spectrum Analysis / Q000295:instrumentation; D013696:Temperature; D013814:Thermal Conductivity; D013816:Thermodynamics; D014835:Volatilization; D014867:Water / Q000737:chemistry
chemical_list: D014867:Water