Simultaneous determination of tetrabutyl ammonium and tetrabutyl phosphonium in environmental water samples by solid phase extraction and ion chromatography

An ion chromatography method by solid-phase extraction which was used for the simultaneous determination of tetrabutyl ammonium ([TBA](+)) and tetrabutyl phosphonium ([TBP](+)) in environmental water samples was developed. The samples were first concentrated and purified through an SCX solid-phase extraction column, and eluted with 0.02 mol L-1 hydrochloric acid-98% methanol (v/v), then analyzed using a carboxylic acid base cation exchange column. The optimized chromatographic conditions were 3 mmol L-1 methanesulfonic acid-20% acetonitrile as the mobile phase, flow rate of 1.2 mL min(-1) and a 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 the peaks was 2.059. The recovery of solid-phase extraction reached 97.1%, the linear regression equations were y = 0.0142x - 0.0132 and y = 0.0195x - 0.0265, the correlation coefficients were r = 0.9996 and r = 0.9997, the detection limits (S/N = 3) were 0.502 mg L-1 and 0.448 mg L-1, the relative standard deviations (n = 5) of the retention times of [TBA](+) and [TBP](+) were 1.22%, 1.23% and of the peak areas were 0.24% and 0.25%, respectively. Recoveries were 94.8% to 103.2%. The method is accurate, rapid, sensitive and efficient for meeting the requirements for quantitative analysis.