Abstract:

Fourier transform infrared(FTIR) spectroscopy is a sensitive probe of molecular structure which can provide significant information on the structure and composition of unknown substances and confirm the presence of some chemical groups. IR fiber optics possesses high performance which can be applied to transmission of IR light. The coupled technique of FTIR and mid-IR fiber optics can simplify the sample preparation in traditional IR spectroscopy. Formation of new compound is observed in situ and reaction process can be monitored on line using FTIR fiber optics technique. In this study, mid-IR fiber optics technique was applied to liquid phase systems and solid/liquid reaction systems. In the liquid phase system, we investigated the saponification reaction of naphthenic acid-octal alcohol-heptane and the formation mechanism of water in oil (w/o) microemulsion during saponification. The interaction between naphthenic acid and octal alcohol was observed. With adding ammonium hydroxide, the peak around 1708 cm^-1 disappeared and the peak at 1548 cm^-1 enhanced and the peak position of water emerged and shifted to 1637 cm^-1 from 1642 cm^-1, which is the position of water molecule in IR spectroscopy. It showed that water is constrained in aqueous droplet of naphthenic acid-octal alcohol-heptane and microemulsion is formed through the saponification. In the solid/liquid reaction system, complexation reaction between o-phthalic acid and europium chloride was investigated. The interaction between o-phthalic acid and EuCl₃ in neural medium was ignored in previous study, but this weak interaction was observed using FTIR fiber optics technique in our present investigation. The results showed that the component and structure of the final complex were effect by the difference of adding sequence. Therefore, FTIR fiber optics technique may become a new method of monitoring chemical reaction in real time.

Key words: FT-mid-IR, Mid-IR fiber optics, Naphthenic acid-octal alcohol-heptane, Complex of europium