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 (EMImBF4) as additive for the simultaneous detection of clenbuterol (CLB), terbutaline (TER), and ractopamine (RAC) in feed. The effects of detection potential, concentration of EMImBF4, pH, and concentration of the running buffer, separation voltage as well as injection time on the separation and detection of these three beta-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) EMImBF4, 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 EMImBF4 into the running buffer resulted in significant improvement in separation selectivity and enhancement in peak currents for those beta-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 beta-agonists in feed sample.