Capillary zone electrophoresis determination of aniline and pyridine in sewage samples using transient isotachophoresis with a system-induced terminator

- Transient isotachophoresis with a system-induced terminator is proposed.
- No external terminating electrolyte is required.
- H+ generated depending on the acid-base balance acts as the terminating ion.
- This on-line concentration method is applicable to high-conductivity samples.
- Limits of detection of aniline and pyridine are less than 50 μg per liter.

Transient isotachophoresis (tITP) with a system-induced terminator (SIT) was developed for capillary zone electrophoresis (CZE) determination of aniline (An+) and pyridine (Py+) in sewage samples. After sample injection, a water vial was set at the sample-inlet side. Then voltage was applied to generate a system-induced terminator (H+). Experiments and simulations revealed a concentration effect by tITP with an SIT: background electrolyte (BGE) - 100 mM acetic acid (AcOH) and 50 mM NaOH (pH 4.6); detection wavelength - 200 nm for An+ and 254 nm for Py+; vacuum injection period - 15 s (190 nL); SIT generation - 10 kV applied for 80 s with the sample inlet side anode; separation voltage - 20 kV with the sample inlet side anode. The limits of detection (LODs, S/N = 3) of An+ and Py+ respectively reached 10 and 42 μg/L, with good repeatability (peak area RSDs ≤ 6.9%) and calibration graph linearity (R2 = 0.9997). The proposed method was applied for determination of An+ and Py+ in sewage samples. Recoveries of An+ (0.50 mg/L) and Py+ (2.0 mg/L) in spiked sewage samples were 94-104%.