Unfortunately, the process of preparing accurate solvent mixtures for the precise calibration of the analyzer under the actual operating conditions is sufficiently difficult and unreliable in many cases, to generally prevent calibration with solvent mixtures.
Only a few solvents have sufficient vapor pressure for reliable and stable pressurized cylinder mixtures for calibration in the LFL range. In multi-solvent mixtures, the possibility of a wide variation in boiling points and vapor pressures can lead to pressure and temperature dependent "fractional" changes in the mixture, and a significant loss of accuracy in the calibration of sensors with a wide variation in responses to different solvents.
Calibration using solvents is a laboratory procedure. Therefore it is important to obtain empirical calibration data from either the manufacturer or from an approval authority for each solvent to be measured. The calculation of response factors from theoretical basis, for example from the carbon content as for a FID sensor, or the thermal content as for a catalytic sensor, can lead to serious errors.