Monitoring of Ambient Ozone : Instrumentations and Applications

This short review provides the recent progresses on continuous monitoring of atmospheric ozone. The analytical performance is defined in US-EPA 40 CFR Part 53, and Federal Equivalent Method for ozone adopts an ultraviolet photometry to meet the definition. Chemical monitoring systems including spectrophotometry with dye bleaching, chemiluminescence, and bioluminescence have been developed to satisfy the analytical performance. Changes in the electric resistance of semiconductors are also utilized for the measurements. Some of the proposed instruments have been applied to the monitoring of ozone in the ambient air, and reliable results are demonstrated

Development of Novel Analysis and Characterization Methods Utilizing Reaction Dynamics in a Separation Capillary

Electrophoretic migration of an analyte in capillary electrophoresis (CE) reflects reaction dynamics of the analyte in solution. In affinity CE, an analyte of interest interacts with a modifier added in the separation buffer in fast equilibrium, and effective electrophoretic mobility of the analyte is contributed from its equilibrium species. Precise measurement of effective electrophoretic mobility allows analyzing the equilibrium. Analysis of equilibria under CE separation possesses several advantages against traditional analyses in homogeneous solution; coexisting substances including impurities and kinetically generated substances are resolved by CE from the equilibrium species of interest. Characteristics of the CE analysis have been applied to analyses of acid-base equilibria of degradable substances and ion-association equilibria in an aqueous solution. Since CE is operated in an open-tubular capillary, it is also suitable for the characterization of carbon nanoclusters such as graphene and carbon nanotube, and measurement of effective electrophoretic mobility helps characterization of nanoclusters. A novel analysis technique of capillary electrophoresis/dynamic frontal analysis (CE/DFA) has also been proposed for the analysis of such reactions as involving equilibria and kinetic reactions. In CE/DFA, kinetically generated product is continuously resolved from the equilibrium species, and a plateau signal would be detected when the reaction rate is constant. Michaelis-Menten constants have successfully been determined through the plateau height by CE/DFA. In this review, analysis and characterization methods utilizing reaction dynamics in a separation capillary are summarized

Kinetic-spectrophotometric method for the determination of trace amounts of bromide in seawater

A novel simple, sensitive and rapid kinetic-spectrophotornetric method is proposed for the determination of trace amounts of bromide. The method is based on its catalytic effect on the oxidation of methylene blue (MB) by hydrogen peroxide in strongly acidic solution. The oxidation reaction is activated by large amounts of chloride and can be monitored spectrophotometrically by measuring the decrease in the absorbance of MB at 746 run. The determination of bromide is performed by a fixed-time method at the first 100 s from the initiation of the reaction. Unlike other kinetic-spectrophotornetric methods for the determination of bromide, the proposed method does not require heating the solution. Bromide can be determined in the range from 80 to 960 mu g l(-1) with the detection limit of 35 mu g l(-1). The relative standard deviation of ten replicate determination of 480 mu g l(-1) bromide was 1.4%. The influence of potential interfering ions was studied. The proposed method was satisfactorily applied to the determination of bromide in seawater without interfering effect from chloride ion.</p

Capillary zone electrophoretic studies of ion association between inorganic anions and tetraalkylammonium ions in aqueous-dioxane media

Ion association between inorganic anions and symmetrical tetraalkylammonium ions, R4N+ (R = Me, Et, Pr, n-Bu, n-Am, and 2-methyl butyl {isoamyl = iAm}) was investigated using ordinary silica capillary by capillary zone electrophoresis. An improved version of the Williams-Vigh method was used for the first time to measure the mobilities of the inorganic anions. Plots of log K-ass against log dielectric constant in various media, revealed a smaller change in K-ass compared to dielectric constant. These plots suggest that the Bjerrum's equation is inadequate in accounting for the associations of ions in a CZE setup. </p

Analysis of Acid Dissociation Equilibrium of Bupropion by Capillary Zone Electrophoresis After Degradation Under Heat

An acid dissociation constant (pKa) of bupropion has been determined in an aqueous solution by capillary zone electrophoresis (CZE). Electrophoretic mobility of bupropion was measured by CZE over its acid-dissociating pH range, and a pKa value has been determined as 8.75±0.02 (mean ± standard error, ionic strength: 0.010 mol dm−3). Although bupropion degrades under heated and alkaline conditions and the degraded species from bupropion coexist in the aqueous solution, the pKa value of bupropion can also be determined by CZE with the residual bupropion without any interference from the degraded species. The pKa value determined after the heat-degradation was 8.74±0.02; the result agreed well with the one determined with the freshly prepared solution. Utilization of the separation characteristics of CZE has been demonstrated with bupropion for the analysis of the fast equilibrium of acid-base reaction under the coexistence of the degraded species

Direct photometric detection of inorganic anions by capillary zone electrophoresis using stacking effect of sulfate ion on sample ions

Stacking effect of sulfate ion on the analysis of inorganic anions by capillary zone electrophoresis was examined during the sample injection period. A used silica capillary was dynamically coated with tetradecyltrimethylammonium bromide (TDTMA(+)Br(-)) to control the electroosmotic flow. Analyte anions were directly detected by photometry at 214 nm. Five kinds of anions, namely bromide, nitrite, nitrate, molybdate, and tungstate, were detected. Anion separation was developed using 4×10(-3) M sodium sulfate in the carrier solution. Peak heights for anions increased along with additional Na(2)SO(4). The stacking effect was more effective for the anions with high mobility than those with low mobility. Calibration graphs for nitrate and nitrite showed good linearity in the concentration range of 10(-6) to 10(-5) M

Migration Behavior of Carbon Nanotube in Capillary Electrophoresis with Sodium Dodecyl Sulfate and Water-Soluble Nonionic Polymer

Single-walled carbon natobube (SWCNT) was dispersed in an aqueous surfactant solution, and the dispersion of CNT was analyzed by capillary electrophoresis (CE). The dispersion was evaluated through a broad peak of the electropherograms, while the aggregation of the CNT was attributed to the shot signals in the electropherograms. Water-soluble nonionic polymer was also added in the separation buffer to examine the dispersion in the surfactant solution as well as to control the migration behavior. Polyethylene glycol, polyvinyl alcohol, and polyvinylpyrrolidone were examined. The electrophoretic mobility of the broad peak got smaller with increasing concentrations of the polymer examined. The theoretical number of plates of the broad peak was improved by the addition of the polymer. Moderately broad peak was preferable for the dispersion of the SWCNT in the surfactant solution

Inhibition Assay of Theophylline by Capillary Electrophoresis/Dynamic Frontal Analysis on the Hydrolysis of p-Nitrophenyl Phosphate with Alkaline Phosphatase

A novel inhibition assay is proposed by capillary electrophoresis/dynamic frontal analysis (CE/DFA). When a substrate of p-nitrophenyl phosphate and an inhibitor of theophylline were tandemly introduced into the capillary containing alkaline phosphatase as an enzyme, two plateau signals were detected in the electropherogram. A higher plateau is based on the CE/DFA without inhibition, and a suppressed plateau is formed under the inhibition while the substrate zone passing through the inhibitor zone. Inhibition constant was successfully determined through the two plateau heights

Determination of Two-Steps Acid Dissociation Constants of L-Ascorbic Acid by Capillary Zone Electrophoresis

Two-steps acid dissociation constants of L-ascorbic acid (AA) were determined through the changes in the effective electrophoretic mobility in capillary zone electrophoresis. Although ascorbic acid is oxidatively degradable in an aqueous solution, especially in alkaline conditions, the effective electrophoretic mobility of AA was successfully measured in the pH range between 1.87 and 11.97. In the analysis of the first-step acid dissociation constant (pKa1) at weakly acidic pH conditions, a coated capillary with 1,3-propanesultone and a pressure-assist were utilized to detect anionic AA. In the analysis of the second-step acid dissociation constant (pKa2) at weakly alkaline pH conditions, AA was successfully detected at the pH range up to 11.97 with the help of Cu catalyst to remove the dissolved oxygen in the separation buffer. Acid dissociation constants were independently determined as pKa1 = 4.15±0.01 and pKa2 = 12.07±0.04 by non-linear least-squares analyses. AA did not fully dissociate at the weakly alkaline pH range, and the effective electrophoretic mobility of the dianion form of AA was extrapolated for the analysis