Subzero-Temoperatur Extraction Of Unstable Organic Compounds

In this paper, subzero-temperature liquid-liquid extraction of organic compounds have been studied, including the extraction of phenolic compounds such as phenol,4-nitrophenol, 2-nitrophenol,2,4-dimethylphenol and bisphenol A in the form of molecules and the extraction of vitamin B1 which was in the form of ions. At the same time, the influencing factors and the optimum conditions were discussed respectively. This thesis is composed of three chapters which are as follows:Chapter 1:On the basic of many references, the commonly used sample preparation techniques were classified. Theoretical basisand the applications of these sample preparation techniques were introduced in this chapter, among which subzero-temperature liquid-liquid extraction was emphasized. The fundamental theory of liquid-liquid extraction, the experimental condition optimization and the influencing factors were included.Chapter 2:For high-performance liquid chromatography of phenols,subzero-temperature extraction technique using hydrophilic acetonitrile as a solvent was applied to the extraction of phenols such as phenol,4-nitrophenol,2-nitrophenol,2,4-dimethylphenol and bisphenol A from water samples. After the factors influencing extraction were investigated, the optimal extraction conditions were determined as follows:3.5mL of water,2.0 mL of acetonitrile, pH at 4.5,30 min of extraction time, and -30℃of extraction temperature. The recovery of the target analytes was between 96.51%-116.17%. The detection limits of phenol,4-nitrophenol, 2-nitrophenol,2,4-dimethylphenol and bisphenol A were 15.79,0.54,0.81,6.00 and 5.00 ng/mL, respectively. As acetonitrile was used as the extraction solvent, this extraction method would be suitable for mass spectrometer detection, and much lower detection limits for the selected phenols would be expected.Chapter 3:A rapid method for the study of extraction effect of vitamin B1 by subzero temperature liquid-liquid extraction-UV/VIS spectrophotometry was developed. At the meantime, the factors which affect the extraction effect of vitamin B1 were discussed and optimized. After the factors influencing extraction were investigated, the optimal extraction conditions were determined as follows:5.0 mL of water phase including vitamin B1 and SDS, 20mmol/L of SDS,6.0 mL of acetonitrile, pH at 4.0,35 min of extraction time, and -30℃of extraction temperature. The concentration of the vitamin B1 in the injecta was 52.18 mg/mL. The detection limit of vitamin B1 was 67.48 ng/mL. The recoveries of the target analytes were between 98.32%-106.85%. It was the key to use SDS in the extraction of vitamin B1. At the same time, the use of SDS made it possible to extract organics which were in the form of ions by this subzero-temperature liquid-liquid extraction.