Constancy of the Calibration Factor

It is commonly assumed that the calibration factor, K, by means of which, according to Eq. (8), the measurement data are converted into the number-average molecular weights, depends only on the solvent, the temperature, and an apparatus constant.  

Wood species Range of molecular weight (Mn) Reference 

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The effect of several operating parameters must be emphasized. They are the size of the drops on the thermistor beads, the response time, and the purity of both solvents and lignin samples. Furthermore, it must be noted that conflicting results have been reported on the constancy of the calibration factor (Bersted 1973, Brzezinski et al. 1973, Kamide et al. 1976, Burge 1979, Marx-Figini and Figini 1980, Kim 1985, Froment and Pla, unpubl. results, 1988). 

Due to the reduced Q factor of the quartz crystals in liquids, and therefore decreased phase slope, the requirements of the circuit with respect to phase (frequency dependence, noise, temperature dependence), to amplification linearity, and to temperature constancy are much higher. One electrode of the quartz crystal should be grounded to minimize parasitic effects and to allow operation of quartz arrays in conductive liquids. The increased damping of the oscillator should be overcome by automatic level control. The control variable in the amplitude control loop can be used as an independent measurement value. It also allows for calibration of/osc with respect to/s [36]. 

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