Determination of phosphate in seawater by CZE with on‐line transient ITP

Abstract

We developed CZE with indirect UV detection for the determination of phosphate in seawater using transient ITP as an on-line concentration procedure. The following optimum conditions were established: BGE, 5 mM 2,6-pyridinedicarboxylic acid (PDC) containing 0.01% hydroxypropylmethylcellulose (HPMC) adjusted to pH 3.5; detection wavelength, 200 nm; vacuum injection period of sample, 3 s (45 nL); terminating ion solution, 500 mM MES adjusted to pH 4.0; vacuum injection period of the terminating ion solution, 30 s (450 nL); applied voltage, 30 kV with the sample inlet side as the cathode. The LOD for phosphate was 16 mg/L (PO 3À 4 -P) at S/N of 3. The respective values of the RSD of the peak area, peak height, and migration time for phosphate were 2.6, 2.3, and 0.34%. The proposed method was applied to the determination of phosphate in a seawater certified reference material for nutrients, MOOS-1, distributed by the National Research Council of Canada (NRC). The results were very similar to certified values. The method was also applied to the determination of phosphate in coastal seawaters. The results agreed with those obtained using a conventional spectrophotometric method.

Analysis of phenolic acids by non-aqueous capillary electrophoresis after electrokinetic supercharging

“…Most of the on-line preconcentration methods in capillary electrophoresis (CE) are based on changes in analyte migration due to conductivity difference, buffer pH difference or the association between the analytes and the surfactants, and the combination of these approaches. Thus methods such as field-amplified sample stacking (FASS) [5][6][7], field-amplified sample injection (FASI) [8], large-volume stacking using the EOF pump (LVSEP) [9][10][11][12][13][14][15][16], fieldamplified sample injection with matrix removal via an EOF pump (FAEP) [17,18], dynamic pH junction (DypH) [19][20][21], transient isotachophoresis (tITP) [22,23], pseudo-transient isotachophoresis (Pseudo-tITP) [24][25][26][27][28], sweeping [29][30][31][32], micelle collapse (MC) [33,34] and various combinations including electrokinetic surpercharging (EKS) [35][36][37][38][39][40][41], selective exhaustive injection [42] and selective exhaustive injection-sweeping (SEI-sweeping) [43][44][45], dynamic pH junction-sweeping [46], and large-volume stacking using the EOF pu...…”

Determination of bromate in highly saline samples using CZE with on‐line transient ITP

“…It was presumed that the transient ITP condition disappeared rapidly because the chloride concentration in the sample solutions was insufficient to maintain the transient ITP lower than 27.2 of salinity. In our investigation, the salinity of coastal seawater was 27 -32 [21]. The difference of peak area and peak height between 27.2 and 34.0 was around 10%.…”

“…The third group was a mixed solution of potassium chloride, sodium hydrogen carbonate, potassium bromide, boric acid, and sodium fluoride. Then the three groups were mixed to give the composition presented in Table 1 of our previous report [21]. Sea salts of two kinds and a commercially available type of rock salt were used.…”

CZE determination of submicromolar level of phenol in seawater using improved dynamic pH junction

“…Distilled, demineralized water, obtained from an automatic still (WG220; Yamato Kagaku, Tokyo, Japan) and a Simpli Lab‐UV high purity water apparatus (Merck Millipore, Tokyo, Japan) was used throughout. Artificial seawater (ASW, salinity 34 at 25°C, pH 7.9) was prepared according to the procedure described in an earlier report . NSW samples were collected from three different sites.…”

“…Various on‐line concentration procedures including dynamic pH junction have been developed to improve the low concentration sensitivity of CZE with conventional UV detection . Dynamic pH junction is applicable to highly saline samples as well as transient ITP . Today, CZE is applied to the detection and quantification of phenolic compounds in surface and reused waters using chemiluminescence or amperometric detection .…”