| An investigation of solid phase extraction and ion-exchange chromatography with conductivity detection was carried out to analyse of tetramethyl ammionium,tetraethyl ammionium,tetrapropyl ammionium,tetrabutyl ammonium and tetrabutyl phosphonium ionic liquid cation. The purpose is to develop simple and fast new methods of determining ionic liquid cation by solid phase extraction and ion–exchange chromatography with conductivity detection. This study mainly contains three parts:Firstly, in this article, a systematic study of tetrabutyl ammonium ionic liquid cation using ion chromatography with conductivity detection had been conducted. The effects of the eluent type, eluent concentration, eluent pH value, column type, column temperature, and flow rate on the determination of tetrabutyl ammonium ionic liquid cation were investigated, and the retention rules were discussed. The optimal chromatographic conditions were 3 mmol/L methanesulfonic acid-40% acetonitrile as eluent, flow rate of 1.0 mL/min and column temperature of 40℃. Under the conditions, the retention time of tetrabutyl ammonium ionic liquid cation was less 4 min. The detection limit(S/N =3) of the method was 0.82 mg/L, the relative standard deviations(n = 5) of retention time and peak area were 0.09% and 1.10%, respectively. The recovery of spiked tetrabutyl ammonium ionic liquid cation was in the range of 98%-100.1%. The method was proved to be accurate, reliable, rapid, and meet the requirements for quantitative analysis of tetrabutyl ammonium ionic liquid samples.Secondly, ion chromatography method by solid-phase extraction which was used for simultaneous determination of tetrabutyl ammonium([TBA]+) and tetrabutyl phosphonium([TBP]+) in environmental water sample was developed. The samples were first concentrated and purified through a SCX solid-phase extraction column, and eluted with 0.02 mol/L hydrochloric acid-98% methanol(v/v), then analyzed by a carboxylic acid base cation exchange column. The optimized chromatographic conditions were 3 mmol/L methanesulfonic acid-20% acetonitrile as mobile phase, flow rate of 1.2 mL/min and column temperature of room temperature. Under these conditions, [TBA]+ and [TBP]+ achieved baseline separation. The retention times of the two cations were 11 min and 14 min, the resolution between peaks was 2.059. The recovery of solid-phase extraction reached 97.1%, the linear regression equations were y = 0.0142 x–0.0132 and y = 0.0195 x–0.0265, the correlation coefficients were r = 0.9996 and r = 0.9997, the detection limits(S/N = 3) were 0.502 mg/L and 0.448 mg/L, the relative standard deviations(n = 5) of retention times of [TBA]+ and [TBP]+ were 1.22%, 1.23% and of peak areas were 0.24%, 0.25%, respectively. Recoveries were 94.8% to 103.2%. The method is accurate, rapid, sensitive and efficient to meet the requirements for quantitative analysis.Finally, a method of solid phase extraction and ion-exchange chromatography with conductivity detection was established for the determination of tetramethyl ammionium,tetraethyl ammionium,tetrapropyl ammionium and tetrabutyl ammonium in the environmental water. In this experiment, a strong cation exchange extraction column was used for sepration and enrichment. The target was eluted by hydrochloric acid- methanol(v/v), the eluent can be chromatographed directly. The final selection of the chromatographic conditions were: 3 mmol/L oxalic acid-20% acetonitrile as eluent, the column temperature was room temperature and the flow rate was 1.2 ml/min. Under this condition, the target could be realized and the better chromatographic peak shapes could be got. In the range of 1.74-100 mg/L, the correlation coefficient of linear regression equation was good. The detection limit(S/N = 3) was 0.552 mg/L. The spiked recoveries of the cations was 97%. The method which has better practicability is simple, it can be used for the detection of tetramethyl ammionium, tetraethyl ammionium,tetrapropyl ammionium and tetrabutyl ammonium in environmental water samples. |
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