Self-reference Analysis Based on Temperature Difference Absorption Spectra

The direct qualitative identification of pure liquids in laboratories and in security checks is generally performed by the detection of the refractive index or the permittivity. However, refractive indices are strongly influenced by temperature, while the permittivities of some organics are difficult to differentiate. On the other hand, the quantitative monitoring of samples with high concentration in plating baths and in chemical production lines are generally performed via a “Sampling – Dilution – Analysis” approach due to significant deviations from the linear range at high concentration, which makes the real-time monitoring of concentrated samples difficult. Here, we propose a self-reference analysis (SRA) method to directly analyze pure liquids and concentrated samples based on temperature difference absorption spectra (TDAS) without the need for dilution. This method was performed by simultaneously scanning the spectra of the reference and the sample, which are both obtained from the same analyte fo...