Capillary zone electrophoresis determination of fluoride in seawater using transient isotachophoresis

Keiichi Fukushi, Yuki Fujita, Junpei Nonogaki, Jun-ichi Tsujimoto, Takanari Hattori, Hideyuki Inui, Vladimir P. Beškoski, Hiroki Hotta, Mitsuru Hayashi, Takeshi Nakano

We developed capillary zone electrophoresis (CZE) with indirect UV detection for the determination of fluoride (F-) in seawater using transient isotachophoresis (tITP) as an on-line concentration procedure. A method of correcting sample salinity effects was also proposed so that F- concentrations were obtained using a calibration graph. The proposed method is simple: it requires no sample pretreatment aside from dilution. The following optimum conditions were established: background electrolyte (BGE), 5 mM 2,6-pyridinedicarboxylic acid (PDC) adjusted to pH 3.5 containing 0.03% m/v hydroxypropyl methylcellulose (HPMC); detection wavelength, 200 nm; vacuum (50 kPa) injection period of sample, 5 s (254 nL); and applied voltage, 23 kV with the sample inlet side as the cathode. The limit of detection (LOD, S/N = 3) and limit of quantification (LOQ, S/N = 10) for F- reached 0.024 and 0.070 mg/L, respectively. The respective values of the relative standard deviation (RSD) of the peak area, peak height, and migration time for F- were 2.5, 3.4, and 0.30%. The proposed method was applied for the determination of F- in seawater samples collected from coastal waters of western Japan during August 26-28, 2014. Both results obtained using standard addition method and a calibration graph agreed with those obtained using a conventional spectrophotometric method.