Range of Compounds and Concentration
The LCU can be employed for calibration of trace gas analyzers over an extensive range of compounds and concentrations.
For trace concentrations, a very low solubility of a compound in water is sufficient to produce an aqueous standard. As an example, this has successfully been achieved for propofol which has a solubility of only 0.12 g/l (25 °C) in water.
The efficient evaporation mechanism enables calibration of compounds even with very low vapor pressures (i.e. semi-volatiles). This has successfully been demonstrated for caffeine and indole (vapor pressure of only 1.6 Pa at 25 °C), which set the current benchmark.
The LCU has successfully been used with a growing variety of compounds, including ketones, aldehydes, alcohols, amines, terpenes, organic acids, and esters.
The LCU has a dynamic range of 100. The resulting concentration in the gas phase is directly dependent on the concentration in the aqueous standard. This allows to explore concentrations up to ‰ or even % and down to the pptv range and below.