1 2 3 4 In - line preconcentration capillary zone electrophoresis for the analysis of haloacetic acids in 5 water

27 Two in-line enrichment procedures (large volume sample stacking (LVSS) and field 28 amplified sample injection (FASI)) have been evaluated for the capillary zone electrophoresis 29 (CZE) analysis of haloacetic acids (HAAs) in drinking water. For LVSS, separation on normal 30 polarity by using 20 mM acetic acid-ammonium acetate (pH 5.5) containing 20% acetonitrile as 31 BGE was required. For FASI, the optimum conditions were 25 s hydrodynamic injection (3.5 kPa) 32 of a water plug followed by 25 s electrokinetic injection (-10 kV) of the sample, and 200 mM 33 formic acid-ammonium formate buffer at pH 3.0 as BGE. For both FASI and LVSS methods, linear 34 calibration curves (r 2 >0.992), limit of detection (LOD) on standards prepared in Milli-Q water 35 (49.1-200 μg/L for LVSS and 4.2-48 μg/L for FASI), and both run-to-run and day-to-day precisions 36 (RSD values up to 15.8% for concentration) were established. Due to the higher sensitive 37 enhancement (up to 310-fold) achieved with FASI-CZE this method was selected for the analysis of 38 HAAs in drinking water. However, for an optimal FASI application sample salinity was removed 39 by solid phase extraction (SPE) using Oasis WAX cartridges. With SPE-FASI-CZE, method 40 detection limits in the range 0.05-0.8 μg/L were obtained, with recoveries, in general, higher than 41 90% (around 65% for monochloroacetic and monobromoacetic acids). The applicability of the SPE42 FASI-CZE method was evaluated by analyzing a drinking tap water from Barcelona where seven 43 HAAs were found at concentration levels between 3-13 μg/L. 44 45 46