Masataka Yamane

Determination of bromide ions in seawater by capillary zone electrophoresis using diluted artificial seawater as the buffer solution

Abstract A novel capillary zone electrophoresis method was developed for the determination of bromide ion in seawater. A tenfold-diluted artificial seawater was adopted as the buffer solution, to prevent interference from high concentrations of chloride ion in seawater. No electroosmotic flow reverser was used to shorten the analysis time. It was found that the peak area and migration time for bromide ion were almost constant, despite differences in the salinity of sample solutions; the peak height decreased linearly with an increase in the salinity. The limit of detection for bromide ion was 0.46 mg/l ( S / N =3). The values of the relative standard deviation for peak area and migration time for bromide ion were 1.4 and 1.5%, respectively. The proposed method was applied to the determination of bromide ion in seawater samples taken from the surface and the sea-bed. The analytical results obtained by the working curve method agreed with those obtained by the standard addition method. The method may be applicable to the determination of other ions, such as nitrite and nitrate ions, in seawater

Simultaneous determination of nitrate and nitrite ions in seawater by capillary zone electrophoresis using artificial seawater as the carrier solution

We are proposing a novel capillary zone electrophoresis for the simultaneous determination of nitrate and nitrite ions in seawater. An artificial seawater was adopted as the carrier solution to eliminate the interference of high concentrations of chloride ion etc., in seawater. For the purpose of reversing the electroosmotic flow, 3 mM cetyltrimethylammonium chloride was added to the carrier solution. A 100 μm I.D. capillary was used to extend the optical path length. Regardless of the salinity of sample solutions, the peak areas and migration times for nitrate and nitrite ions were within ±3%, while the peak heights for these ions decreased linearly with increasing salinity of sample solutions. The limits of detection for nitrate and nitrite ions were 0.04 and 0.07 mg/l (S/N=3, based on three-times the baseline noise), respectively. The values of the relative standard deviation (RSD) of peak areas for these ions were 1.5 and 2.4%. The RSDs of migration time for these ions were 0.85 and 0.78%. The proposed method was applied to the determination of nitrate and nitrite ions in seawater samples taken from the surface and the seabed. The recovery of nitrate and nitrite ions was 97-114%.

Ionization of dichlorophenols for their analysis by capillary electrophoresis-mass spectrometry.

In order to develop an advanced analytical method using capillary electrophoresis (CE) for non-volatile environmental pollutants such as endocrine disruptors, combination with mass spectrometry (MS) is necessary for their identification. We chose dichlorophenols (DCPs) as test samples because one of their isomers, 2,4-DCP, is suspected to have endocrine disrupting effects. A preliminary study on their separation by CE-MS was performed using a laboratory-made electrospray ionization (ESI) interface. For the effective ionization of 2,4-DCP at the

Determination of ascorbic acid in vegetables by capillary zone electrophoresis

Capillary zone electrophoresis (CZE) was used for the determination of ascorbic acid (AsA) in vegetables. AsA was extracted from vegetables by homogenizing with 2% thiourea–10 mM hydrochloric acid and determined directly by CZE with a borate buffer. The limit of detection (LOD) for AsA was 0.35 mg/l (S/N=3). Relative standard deviations of peak area and migration time for AsA in vegetables were 8.7 and 0.3%, respectively. Recovery of AsA was 97–112%. AsA concentrations in various vegetables were determined by the method. The method was also used for the determination of AsA in vegetables that had been cultivated by using fermented blue mussels, to examine their usefulness as a fertilizer for vegetables.

Effect of alkyl chain length of sodium N-acyl sarcosinates on migration behavior in micellar electrokinetic chromatography

Application of sodium N-acyl sarcosinates for micellar electrokinetic chromatography was investigated. Three homologous sodium N-acyl sarcosinates were able to be used as pseudo-stationary phase. The migration behavior of some aromatic test samples was investigated with these surfactants under the same micellar concentrations. The migration time window became wider as the alkyl chain length of surfactant decreased. The capacity factors increased with an increase in the alkyl chain length of surfactant. Three sarcosinates gave almost the same separation selectivity for hydrophilic solutes. The separation selectivity for hydrophobic solutes was slightly different from one another.

Analysis of dyestuff degradation products by capillary electrophoresis.

Capillary electrophoresis (CE) with two different detection methods, mass spectrometry (MS) and UV absorption spectroscopy with photodiode array detection (UV/DAD), was used for the analysis of the degradation products of dyestuffs. We have studied wet oxidation with solid catalyst as the treatment method of wastewaters containing dyestuffs. When the Orange II (C.I. Acid Orange 7) solution was used as the model wastewater, treated solution contained unknown highly polar degradation products. We were able to determine the molecular masses of some products by CE-MS. From this clue, we tried to identify these products by CE-UV/DAD. By means of the comparison of the migration time and UV spectra of standard samples, three degradation products were identified. The separation of degradation products was successful within 15 min.

Effect of the polar groups of anionic surfactant on migration behavior in micellar electrokinetic chromatography

Abstract Three kinds of anionic surfactants with different polar groups were used as the pseudo-stationary phase in micellar electrokinetic chromatography (MEKC). We found that sodium N-lauroyl-N-methyl-β-alaninate (ALE) can be used as a pseudo-stationary phase in MEKC, as well as sodium N-lauroyl-N-methyltaurate (LMT) and sodium dodecyl sulfate (SDS). The ionic groups are carboxylate, sulfonate and sulfate, respectively. ALE and LMT have amido linkages. The migration behavior of aniline derivatives and phenol derivatives was investigated with these surfactants. The difference in the migration behavior was compared in terms of the capacity factor. Surfactants with amido linkages showed different selectivity from SDS, for phenol derivatives. The three surfactants also gave different selectivity for aniline derivatives. Changing the buffer pH affected greater the migration behavior of aniline derivatives with SDS than those with ALE and LMT. The correlation of the capacity factor and the octanol-water partition coefficient for each solute was also investigated. Correlation with ALE was the highest among the three surfactants.

Use of several anionic surfactants for the separation of aniline derivatives in micellar electrokinetic chromatography

The separation of 13 aniline derivatives by micellar electrokinetic chromatography (MEKC) with four anionic surfactants was demonstrated. We used sodium dodecyl sulfate (SDS), sodium N-lauroyl-N-methyl-β-alaninate (ALE), sodium N-lauroyl-N-methyltaurate (LMT) and sodium laurylsulfoacetate (LSA) as surfactants. The first application of LSA to MEKC was described. The surfactants having amido linkages, ALE and LMT, gave better separation than SDS. LSA has an ester linkage and its ionic group is sulfonate. Separation with LSA was also better than that with SDS. LSA showed different selectivity from the other surfactants. The effect of the linkages on migration behavior was investigated.

Methods for the preparation and characterisation of a selenocyanate ion-sensitive field effect transistor with Urushi as the membrane matrix

A selenocyanate ion-sensitive field effect transistor (ISFET) was fabricated from a silicon wafer with Urushi (natural lacquer) as the membrane matrix. The proposed ion sensor has excellent durability for over 2 months. The ISFET can be characterised by the relationship between the square root of the drain current and the logarithm of the ion activity in the saturation region of the ISFET. It was found that the linear response range of the Urushi ISFET was from 10–5 to 10–1M selenocyanate ion activity and the selectivity coefficients were almost the same as those of the Urushi ion-selective electrode.

Studies on pH and Nitrate Checkers Made of Semiconductor Devices for Acid Rain Monitoring

Ion-selective field-effect transistors (ISFETs), which are integrated devices for ion-selective electrodes using solid-state microelectronics technology, have attracted much attention for convenient monitoring of acid rain, since conventional analytical procedures are time-consuming. In this paper, some recent results of studies on pH and nitrate checkers made of ISFETs using new sensing materials and their application to samples of acid rain are described.A new pH-sensitive film, TiN was deposited onto the gate of ISFET device using RF plasma-enhanced CVD method. The plasma was generated in a mixture of TiCl4, N2 and H2 gases. The prepared pH-ISFETs showed a linear response and the almost theoretical slope sensitivity of 59 mV per pH change with a rapid response of less than 10 seconds. We have obtained fairly good agreement with the pH values using conventional pH glass electrode. A prototype nitrate-checker was prepared with casting newly designed nitrate-sensing materials, plasticizers and PVC based tetrahydrofuran solution onto the ISFET device. We have obtained good agreement with the values using conventional ion-chromatography at mg L−1 level.