Method and device for determination of moisture content and solid state phase of solids using moisture sorption gravimetry and near infrared or Raman spectroscopy
View Patent ↗A method and apparatus for measuring isotherms and determining solid state phase changes comprising a humidity generator having a temperature controlled internal chamber, a microbalance mounted externally to the internal chamber and a near infrared spectroscopy (NIRS) probe or Raman spectrometer probe mounted internally in the internal chamber, such that the mass of a sample suspended within the chamber and its solid state phase can be determined without disturbing the controlled environment surrounding the sample. The humidity generator includes means for controlling humidity and temperature within the internal chamber, an access port that extends into the internal chamber. The balance is situated near the port such that the balance mechanism extends within the internal chamber. The balance mechanism utilizes a means for holding a sample within the chamber such that the mass of the sample can be determined as it equilibrates to the temperature and relative humidity maintained within the internal cavity. The NIRS probe extends from a NIR spectrometer. Similarly, the Raman probe extends from a Raman spectrometer.
1. An apparatus for measuring isotherms comprising:
a humidity generator having an internal cavity;
means for adjusting humidity and temperature within the internal cavity;
upper and lower ports that extends into the internal cavity;
a balance situated near the upper port such that the balance mechanism extends within the internal cavity;
holding means such that the balance mechanism holds a sample within the cavity and is invisible to measurement wavelengths;
a probe that extends into the internal cavity and is adjacent to the holding means such that one or more spectra of the sample may be acquired via the measurement wavelengths;
means for determining the mass of the sample on the balance mechanism while the sample remains within the cavity and for determining when a final mass is reached wherein changes in the mass fall below predetermined amount;
means for acquiring the one or more spectra from the sample; and
means for placing the humidity generator through a sequence of environments.
2. The apparatus of claim 1 further comprising means for maintaining the internal cavity at a constant temperature and relative humidity until the sample's mass reaches equilibrium.
3. The apparatus of claim 1 further comprising means for ramping the environment within the generator to a new condition and for measuring the mass of the sample until equilibrium is again reached.
4. The apparatus of claim 1 wherein the probe is a NIR probe and the spectra is a NIR spectra.
5. The apparatus of claim 1 wherein the probe is a Raman probe and the spectra is a Raman spectra.