In sorption-effect chromatography, small changes in gas flow rate are measured. These changes indicate both the amount sorbed when a sample enters a column and the amounts desorbed when resolved bands leave. We use a differential capillary meter to measure these changes. Random temperature fluctuations in the apparatus can also cause small changes in flow rate. This “thermal noise” tends to hide the signal. Even when the carrier gas is not sorbed, temperature fluctuations make the flow rate fluctuate by causing expansion and contraction of the apparatus and carrier gas and also by changing the gas viscosity. When the carrier gas is sorbed in the columns, the noise is magnified because the temperature changes cause sorption and desorption, thus increasing the size of the flow-rate fluctuations. We offer advice on the minimization of thermal noise and describe design modifications that reduce thermal noise.
- therrmal noise
- gas flow rate