Figure 3: Vapour-concentration-dependent signals of LC-based chirality.

The values of eez* (mean±r.m.s.) are plotted against relative vapour concentration c_r for different chiral vapours of enatiopure β-pinene, limonene, carvone, terpinen-4-ol and menthol. The flow rate r is 0.33 ml s⁻¹. As a NLC, ZLI-1132 is used here. Broken lines are guides for visibility. For β-pinene, limonene and carvone, the eez* values are saturated at higher c_r. The detection limits for, for example, β-pinene and carvone are very low; c_r ~0.001 and 0.01, corresponding to ~3 and ~5 p.p.m., respectively. Using the plots here as the calibration curves, ee or c_r can be estimated for the analyte vapours for fixed flow rate. (Inset) The identical data are plotted with rescaled c_r, demonstrating the universality of the response curves with sublinear dependence of eez on the chiral vapour concentration. The theoretically predicted curve (see Methods) is also shown as a solid blue line, indicating the qualitative agreement.