title: Complex dielectric properties of microcrystalline cellulose, anhydrous lactose, and α-lactose monohydrate powders using a microwave-based open-reflection resonator sensor.
abstract: The real (ε') and imaginary (ε″) components of the complex permittivity of anhydrous lactose and microcrystalline cellulose (MCC) under different bulk densities, moisture contents (MCs), and times of hydration (for anhydrous lactose) were measured nondestructively using a microwave resonator sensor operating in the range of 700-800 MHz. Measurements of sensor resonant frequency and conductance allow, through calibration, determination of the complex dielectric properties ε' (relative permittivity) and ε″ (relative dielectric loss) of the test material. Characteristic graphs of ε″ versus ε' - 1 curve for each powder were generated as a function of bulk density and MC. Such data can be used to develop empirical models for the simultaneous in situ measurement of the bulk density and MC of the powders. Unlike MCC, anhydrous lactose is converted to its hydrate form in the presence of moisture, which causes a reduction in the amount of physisorbed and "free" water and a subsequent change in the dielectric properties. For powders such as anhydrous lactose that can form a crystal hydrate in the presence of moisture, a combination of techniques such as vibrational spectroscopy together with microwave resonator measurements are appropriate to characterize, in situ, the physical and chemical properties of the powder.
authors.affiliation: Department of Chemical Engineering, Purdue University, West Lafayette, Indiana 47907, USA.
authors.forename: Pei-Fang
authors.initials: PF
authors.lastname: Sung
authors.forename: Yi-Ling
authors.initials: YL
authors.lastname: Hsieh
authors.forename: Kristen
authors.initials: K
authors.lastname: Angonese
authors.forename: Don
authors.initials: D
authors.lastname: Dunn
authors.forename: Ray J
authors.initials: RJ
authors.lastname: King
authors.forename: Rachel
authors.initials: R
authors.lastname: Machbitz
authors.forename: Andrew
authors.initials: A
authors.lastname: Christianson
authors.forename: William J
authors.initials: WJ
authors.lastname: Chappell
authors.forename: Lynne S
authors.initials: LS
authors.lastname: Taylor
authors.forename: Michael T
authors.initials: MT
authors.lastname: Harris
mesh_terms: D002482:Cellulose / Q000737:chemistry*; D002626:Chemistry, Pharmaceutical; D058266:Dielectric Spectroscopy; D004553:Electric Conductivity; D004867:Equipment Design; D005079:Excipients / Q000737:chemistry*; D007785:Lactose / Q000737:chemistry*; D008872:Microwaves; D008956:Models, Chemical; D011208:Powders; D013059:Spectrum Analysis, Raman; D013678:Technology, Pharmaceutical / Q000295:instrumentation* / Q000379:methods; D014159:Transducers; D014732:Vibration; D014867:Water / Q000737:chemistry
chemical_list: D005079:Excipients; D011208:Powders; D014867:Water; D002482:Cellulose; D007785:Lactose; C109691:microcrystalline cellulose