Applicability of Micellar Electrokinetic Chromatography with a Double-Chain Surfactant Having Two Sulfonate Groups to the Determination of Pollutant Phenols in Water

Hiroya HARINO, Shinji TSUNOI, Toshiyuki SATO, Minoru TANAKA
2000 Analytical Sciences  
Micellar electrokinetic chromatography (MEKC) is attracting much attention as a method for separating a wide range of neutral compounds owing to its rapid run-times, extremely high separation efficiency and low sample requirements. During the past several years, the number of publications on MEKC analysis has significantly increased. Especially, MEKC is often applied to the analysis of neutral compounds in the environment. [1] [2] [3] Phenolic compounds, a case in point, are of great
more » ... al concern because of their high toxicity, even at low concentrations and common use. So far, phenols in water have been determined by GC/MS after derivatization to, for instance, their t-butyldimethylsilyl 4 or acetylated 5 derivatives. They are also measured directly (without derivatization) by HPLC with UV 6,7 or electrochemical 6 detection and by SFC 8 with photodiode array detection. Along with capillary-zone electrophoresis, MEKC has also been employed to separate certain phenols. 9, 10 To our knowledge, the eleven priority phenols (EPA phenols) cannot be completely separated in HPLC. In a previous paper, 11 we described the complete baseline separation of EPA phenols by MEKC with a double-chain surfactant having two sulfonate groups: disodium 5,13-bis(dodecyloxymethyl)-4,7,11,14-tetraoxa-1,17-heptadecanedisulfonate (DBTHP). Therefore, it is of great interest to preliminarily investigate the applicability of this MEKC with DBTHP for the simultaneous determination of the EPA phenols in water. In this work, after the EPA phenols were spiked into river water and seawater, they were extracted using solid-phase extraction (SPE); their recoveries were then evaluated by MEKC. Experimental Apparatus MEKC was performed with a P/ACE 5010 capillary electrophoresis system (Beckman, California, USA) using an uncoated fused-silica capillary tube (57 cm × 50 µm i.d., 50 cm from inlet to the detector). The separation temperature and applied voltage were held constant at 35˚C and 20 kV, respectively. The EPA phenols were detected by UV absorption at 214 nm. The micellar solution was prepared by dissolving DBTHP (7.5 mM) in a buffer solution of 50 mM sodium dihydrogenphosphate-25 mM sodium tetraborate at pH 7.0. Sample solutions were injected into the MEKC apparatus by a pressure mode for 2 s (ca. 2 nl). All experiments were performed in duplicate to ensure reproducibility. Data analysis and collection were accomplished using a Compaq PROLINEA 4/66 computer and Beckman P/ACE software, GOLD. Reagents Figure 1 shows the structure of the double-chain surfactant, DBTHP, used in this work. It was synthesized as previously reported. 12,13 All other reagents were of analytical-reagent grade and were used as received. SPE procedure SPE cartridges (Excelpack SPE-UNI/154) were conditioned by successively washing with 10 ml of acetone and 10 ml of distilled water. Then, 500 ml of a water sample acidified in advance to pH 2 with 1 M HCl was loaded at a flow-rate of 10 ml/min. The cartridge was washed with 100 ml of water. After dehydrating the cartridge for 10 min by centrifugation, the adsorbed phenols were eluted with 5 ml of acetone. The eluate was reduced to 1.0 ml under a gentle stream of nitrogen. An aliquot of this solution containing desorbed phenols was subjected to MEKC. Results and Discussion As shown in Fig. 2A , the eleven EPA phenols (1 mM each) could be readily baseline separated with 7.5 mM DBTHP in the separation buffer at pH 7.0. Table 1 gives the results of 1349 Fig. 1 Structure of a double-chain surfactant, DBTHP.
doi:10.2116/analsci.16.1349 fatcat:kititaohezd5vab4o73mpt4ace