Analysis Of Residual Imidazolium-based Ionic Liquids In Water And Soil Samples

Ionic liquids?ILs? are a new type of salt-like materials that are liquids at room temperature. Their structure can be easily tuned, so changing the combinations of different cations and anions can be used to synthetize different ILs. Due to their unique structures they have many unique physical and chemical properties, such as wide range of dissolution, nonvolatility, good conductivity, low vapor pressure and good thermal stability. Therefore, ILs are widely used in various technological applications, such as, organic synthesis, electrochemistry, new material, catalysis, separation and extraction. In recent years, the toxicity of ILs has drawn growing attentions. However, there are few reports focus on the extraction method of ILs in environmental samples. In view of the large number of ionic liquid synthesis and application. ILs are stable in environment due to their poor biodegradability. Therefore, establishing an efficient, accurate and high sensitivity extraction methods and separation techniques have a certain practical significance.In this paper, the analysis metheds of 12 kinds of imidazolium-based ILs were established. And study residue analysis method on 12 kinds of imidazolium-based ILs in water and 9 kinds of imidazolium-based ILs in the soil. Main research contents and conclusions were presented as follows:?1? The methods of UV: ILs([C₄mim]Cl, [C₆mim]Cl, [C₈mim]Cl, [C₁₀mim]Cl, [C₁₀mim]BF4, [C₄mim]BF4, [C₆mim]BF4, [C₈mim]BF4) were measured using a spectrophotometer at 212 nm wavelength conditions with deionized water as a reference. ILs([C₄mim]Br?[C₆mim]Br?[C₈mim]Br?[C₁₀mim]Br) were measured at 212 nm wavelength conditions with deionized water as a reference.?2? The methods of HPLC: HPLC analyses were using Agilent 1100 with an Agilent tunable absorbance ultraviolet detector, equipped with a reversed-phase column Eclipse XDB-C18?250mm×4.6 mm, 5?m?, maintained at 30?. The concentrations of ILs were detected at 212 nm. Samples were analyzed at a flow rate of 0.8m L/min and the injection volume was 10?L. Due to the alkyl side chains of carbon atoms the ratio of the mobile phase is different. As follows:?1? The mixture of methanol?30%,v/v? with 25mmol/L of phosphate buffer?KH2PO4/H3PO4? in 0.5% triethylamine?p H 3.0? was used as the mobile phase for the analysis of [C₄mim]R?R=Cl-, Br-, BF4-?.?2? The mixture of acetonitrile?30%,v/v? with 25mmol/L of phosphate buffer?KH2PO4/H3PO4? in 0.5% triethylamine?p H 3.0? was used as the mobile phase for the analysis of [C₆mim]R?R=Cl-, Br-, BF4-?.?3? The mixture of acetonitrile?35%,v/v? with 25mmol/L of phosphate buffer?KH2PO4/H3PO4? in 0.5% triethylamine?p H 3.0? was used as the mobile phase for the analysis of [C₈mim]R?R=Cl-, Br-, BF4-?.?4? The mixture of acetonitrile?40%,v/v? with 25mmol/L of phosphate buffer?KH2PO4/H3PO4? in 0.5% triethylamine?p H 3.0? was used as the mobile phase for the analysis of [C₁₀mim]R?R=Cl-, Br-, BF4-?.?3? By comparing the two methods, HPLC standard curve had a strong correlation?R2?0.999?. The instrument detection limit was 10-10 g. In this study the sample was determined by using HPLC.?4? In water samples, set up four concentrations?0.1,1,10 and 100mg/L?. The average recovery of ILs was 90.46%-108.83% and the range of C.V was 0.51%-9.07%. This method can satisfy the requirement of residue analysis.?5? In soil samples, by using one-factor-at-a-time?OFAT? experiments and Response Surface Methodology, the extraction method of ILs in the sample was optimized. A BoxBehnken design program was used to design the experiment. Finally, the model was established to measure the significance among these factors. At the same time, a response surface was generated to analysis the pairwise interactive effects on the function. The results showed that the optimum condition of the extraction method for ILs: the ratio of methanol and saturated ammonium chloride was 90:10, the reaction time was 50 min and the ultrasonic power was 350 W. Under these conditions, the average recovery of 9 kinds of ILs was 70.39%-85.30% and the range of C.V was 0.50%-9.99%. This method can satisfy the requirement of residue analysis.The present study could provide useful methods to determine the ILs concentrations in environment.