Dielectric spectroscopy of low-loss sugar lyophiles: I. A methodical approach to measurement in the frequency domain 10-1-106 Hz

This paper is the first in a series devoted to the study of dielectric properties of lyophilized disaccharides with a range of moisture contents. The paper addresses a number of methodical issues with frequency-domain dielectric measurements of low-loss powders, such as lyophilized sugars, in the frequency range from 10-1 to 106 Hz. The principle issue that one encounters with such measurements stems from the perturbation introduced by the apparatus function, which can mask the response of the sample above 10 kHz. Two methods of correction of this apparatus function are investigated. In the first (the 'subtraction' method) a low temperature spectrum of the sample is used for correction. In the second (the 'reference' method) additional measurements of two non-dispersive references are used for correction. Both methods are shown to extend the experimental frequency range. The upper frequency limits for the subtraction and reference methods are 100 kHz and 1 MHz, respectively. Other issues, such as the selection of an optimal measurement cell capacitance (∼4.5 pF), the optimal amount of sample (∼0.3-0.5 g) and the accurate compensation of the stray capacitance (∼2 pF) are discussed