Application of ionic liquid as additive in determination of three β-agonists by capillary electrophoresis with amperometric detection

CE coupled with amperometric detection method was developed using ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF 4 ) as additive for the simultaneous detection of clenbuterol (CLB), terbutaline (TER), and ractopamine (RAC) in feed. The effects of detection potential, concentration of EMImBF 4 , pH, and concentration of the running buffer, separation voltage as well as injection time on the separation and detection of these three β -agonists were investigated in detail. Under the optimum conditions: the detection potential at 1.05 V, 50 mmol/L Tris-HAc at pH 8.0 with 0.6% (v/v) EMImBF 4 , electrokinetic injection 6 s at 16 kV and separation voltage at 16 kV, a baseline separation for these three analytes could be achieved within 11 min. Introduction of EMImBF 4 into the running buffer resulted in significant improvement in separation selectivity and enhancement in peak currents for those β -agonists, especially for TER and RAC, which could not be separated in the running buffer without additive. The method exhibited wide linear range with LOD (S/N = 3) of 2, 1, and 2 nmol/L for CLB, TER, and RAC, respectively. The precision was determined in both intraday ( n = 5) and interday ( n = 3) assays, and the RSDs for both migration time and peak current were less than 6%. The proposed method was also applied to analyze β -agonists in feed sample.