Ultra-sensitive HPLC-photochemical reaction-luminol chemiluminescence method for the measurement of secondary amines after nitrosation.

A novel method for the determination of secondary amines at the nanomolar level was developed. The method is based on the nitrosation reaction of secondary amines, with the generated N-nitrosamines being measured using an HPLC separation, photochemical reaction, and chemiluminescence detection system. The efficient nitrosation of secondary amines was performed using sodium nitrite (200 mM) and acetic acid (0.

Rapid method for monitoring N-nitrosodimethylamine in drinking water at the ng/L level without pre-concentration using high-performance liquid chromatography-chemiluminescence detection.

As a contaminant in drinking water, N-nitrosodimethylamine (NDMA) is of great concern because of its carcinogenicity; it has been limited to levels of ng/L by regulatory bodies worldwide. Consequently, a rapid and sensitive method for monitoring NDMA in drinking water is urgently required. In this study, we report an improvement of our previously proposed HPLC-based system for NDMA determination.

Fluorescent character of Cu(I/II) complexes with bisquinoline-based ligands and fluorometric detection of reductants.

The fluorescence ligands N,N'-bis(2-methylquinolyl)dimethylethylenediamine (BQDMEN) and N,N'-bis(2-methylquinolyl)dimethyl-1,3-propanediamine (BQDMPN) were synthesized. [Cu(II)(bqdmen)](2+) and [Cu(II)(bqdmpn)](2+) were prepared, and their reduction to [Cu(I)(bqdmen)](+) and [Cu(I)(bqdmpn)](+) was confirmed by the observed UV-Vis spectral change. Then, the fluorescence of [Cu(I/II)(bqdmen)](+/2+) and [Cu(I/II)(bqdmpn)](+/2+) in aqueous solution was characterized; [Cu(I)(bqdmen)](+) and [Cu(I)(bqdmpn)](+) were found to fluoresce in aqueous solution, whereas the fluorescence of [Cu(II)(bqdmen)](2+) and [Cu(II)(bqdmpn)](2+) was completely quenched.

Chemiluminescence detection of glucose using Ce(IV) oxidation in a batch system.

A chemiluminescence method for the determination of glucose (GC) using a batch system made in our laboratory is proposed. The method is based on measures of the chemiluminesence intensity from a batch of sample GC solutions following the injection of an (NH(4))(2)[Ce(NO(3))(6)]-[Ru(bpy)(3)]Cl(2) solution. The effect of the Ru complex concentration on chemiluminescence was studied.

Simultaneous determination of pyridine-triphenylborane anti-fouling agent and its degradation products in paint-waste samples using capillary zone electrophoresis with field-amplified sample injection.

We proposed a capillary zone electrophoresis (CZE) procedure using field-amplified sample injection (FASI) for the simultaneous determination of pyridine-triphenylborane (PTPB) and its degradation products: diphenylborinic acid (DPB), phenylboronic acid (MPB), and phenol. The LODs for PTPB, DPB, MPB, and phenol were, respectively, 0.85, 0.

Sensitive determination method for mercury ion, methyl-, ethyl-, and phenyl-mercury in water and biological samples using high-performance liquid chromatography with chemiluminescence detection.

A sensitive determination method for mercury speciation analysis was developed. Four mercury species, mercury ion, methylmercury, ethylmercury, and phenylmercury, were complexed with emetine-dithiocarbamate (emetine-CS(2)), and then injected onto a HPLC instrument coupled with a tris(2,2'-bipyridine)ruthenium(III) chemiluminescence detection system. The emetine-CS(2) complexing agent was effectively used to measure the concentration in addition to serving as a separation and detection reagent.

A novel hybrid mode of sample injection to enhance CZE sensitivity for simultaneous determination of a pyridine-triphenylborane anti-fouling agent and its degradation products.

We developed a novel hybrid sample injection mode (HSIM) that presents the combination of electrokinetic injection and vacuum injection to enhance detection sensitivity in CZE. Samples were introduced using both vacuum and electrokinetic injections simultaneously, with a water plug injected into the capillary prior to sample introduction (i.e.

Rapid method for simultaneous determination of nitrite and nitrate in water samples using short-column ion-pair chromatographic separation, photochemical reaction, and chemiluminescence detection.

A rapid method has been developed for the simultaneous determination of nitrite and nitrate. The separation of nitrite and nitrate was achieved using an octadecylsilane (ODS) short column (5 µm, 20 × 4.6 mm) with 10 mM of borate buffer-methanol (99.

Simultaneous determination of a pyridine-triphenylborane anti-fouling agent and its estimated degradation products using capillary zone electrophoresis.

A commercial organoborane compound, pyridine-triphenylborane (PTPB), is often applied to ship hulls as an anti-fouling agent. We developed capillary zone electrophoresis (CZE) with direct UV detection for the simultaneous determination of PTPB and its estimated degradation products: diphenylborinic acid (DPB), phenylboronic acid (MPB), and phenol. The limits of detection (LODs) for PTPB, DPB, MPB, and phenol were, respectively, 25, 30, 50, and 29 microg/l at a signal-to-noise ratio of three.

Selective determination method for measurement of nitrite and nitrate in water samples using high-performance liquid chromatography with post-column photochemical reaction and chemiluminescence detection.

A simple, sensitive and selective method for the simultaneous determination of nitrite and nitrate in water samples has been developed. The method is based on ion-exchange separation, online photochemical reaction, and luminol chemiluminescence detection. The separation of nitrite and nitrate was achieved using an anion-exchange column with a 20mM borate buffer (pH 10.

Effect of a carboxyl group on the chemiluminescent reaction of tris(2,2'-bipyridine)ruthenium(III) with aliphatic amines.

The effect of a carboxyl group beside nitrogen of aliphatic amines on the tris(2,2'-bipyridine)ruthenium(III), Ru(bpy)(3)(3+), chemiluminescent reaction was examined. It has been shown that a carboxylate anion promotes the chemiluminescent reaction at a lower pH and then the aliphatic amines with this substituent can be sensitively detected compared with corresponding aliphatic amines without this substituent. Based on this finding, preliminary studies on simultaneous determination of 4-hydroxyproline, N-methylglycine, N-methylalanine, proline, and pipecolic acid in human serum have been performed using isocratic reversed-phase ion-pair high-performance liquid chromatography (HPLC) with electrogenerated Ru(bpy)(3)(3+) chemiluminescent detection.

Highly sensitive method for determination of N-nitrosamines using high-performance liquid chromatography with online UV irradiation and luminol chemiluminescence detection.

A new method for the measurement of N-nitrosamines in part-per-trillion concentrations from water samples without preconcentration steps has been developed. This method is based on online UV irradiation after high-performance liquid chromatographic separation and subsequent luminol chemiluminescence detection without addition of an oxidant. It was confirmed that N-nitrosamines in basic aqueous solution were transformed to peroxynitrite by UV irradiation.

Electrogenerated chemiluminescence reaction of tris(2,2'-bipyridine)ruthenium(II) with 2,5-dimethylthiophene as co-reactant in aqueous solution.

A novel effective co-reactant for electrogenerated chemiluminescence (ECL) of Ru(bpy)(3)(2+) has been found. Alpha-position-dialkylated thiophene derivatives such as 2,5-dimethylthiophene (DMT) could be used as a co-reactant for Ru(bpy)(3)(2+) ECL. The reaction mechanism of the Ru(bpy)(3)(2+)/DMT system was proposed on the basis of the identification of the reaction product, the relationship between the molecular structure and the chemiluminescent intensity, and the electrochemical study.

A single-bead analysis on a disk-shaped microfluidic device using an antigen-immobilized bead.

A disk-shaped microfluidic device (lab-on-a-Disk) was developed to allow the evaluation of mental stress. As a standard sample, secretory immunoglobulin A (sIgA), which is a candidate marker of mental stress, was measured by a heterogeneous enzyme immunoassay (EIA) on the lab-on-a-Disk. Centrifugal force provided a microfluidic control on the lab-on-a-Disk.

Chemiluminescence detection of five-membered heteroaromatic compounds using electrogenerated tris(2,2'-bipyridine)-ruthenium(III).

Heteroaromatic compounds, such as 2,5-dimethylthiophene, 2,5-dimethylpyrrole, and 2,5-dimethylfuran, were found to act as reducing agents for the tris(2,2'-bipyridine)ruthenium(III), Ru(bpy)3(3+), chemiluminescent reaction. In order to characterize the chemiluminescent reaction of Ru(bpy)3(3+) with heteroaromatic compounds, we have investigated various mono-, di-, and tri-heteroaromatic compounds. The pi-electron density and stability of aromatic rings influence the chemiluminescent efficiency of the reaction.

Highly sensitive and simple method for measurement of pipecolic acid using reverse-phase ion-pair high performance liquid chromatography with tris(2,2'-bipyridine)ruthenium(III) chemiluminescence detection.

A new, highly sensitive chemiluminescence method for measurement of pipecolic acid in various substances such as human serum, cow's milk, beer, and apple juice has been developed. The method is based on reverse-phase ion-pair high performance liquid chromatographic separation and subsequent tris(2,2'-bipyridine)ruthenium(III) chemiluminescence detection. It was confirmed that imino acids show strong chemiluminescence upon mixing with tris(2,2'-bipyridine)ruthenium(III).

High-throughput nitric oxide assay in biological fluids using microchip capillary electrophoresis.

In order to develop a high-throughput screening method for the nitrogen monoxide metabolites, nitrite and nitrate, in biological fluids, we have investigated the simultaneous determination of these metabolites using microchip capillary electrophoresis (MCE). In this study, the control of applied voltage to obtain higher sensitivity by increasing the sample injection volume was investigated. Also, the improvement of reproducibility by correcting the injection volume using the internal standard was investigated.

High-performance liquid chromatography of aromatic compounds with photochemical decomposition and tris(2,2'-bipyridine)ruthenium(III) chemiluminescence detection.

A novel high-performance liquid chromatographic method for the determination of aromatic compounds based on the on-line photochemical degradation and subsequent tris(2,2'-bipyridine)ruthenium(III) chemiluminescence detection has been developed. Chemiluminescence intensity depended upon the number of aromatic rings, UV irradiation time, and variety of substituted functional groups. One of the decomposition products of aromatic compounds by UV irradiation was identified as oxalic acid.

Determination of ammonium in river water and sewage samples by capillary zone electrophoresis with direct UV detection.

We developed capillary zone electrophoresis (CZE) with direct UV detection for determination of ammonium in environmental water samples. Ammonium in the samples was partly converted into ammonia in the alkaline background electrolyte (BGE) during migration and was detected by molecular absorption of ammonia at 190 nm in approximately 7 min. The limit of detection (LOD) for ammonium was 0.

Simple and sensitive method for determination of glycoalkaloids in potato tubers by high-performance liquid chromatography with chemiluminescence detection.

A novel, simple and sensitive high-performance liquid chromatographic method for the determination of the potato glycoalkaloids, alpha-solanine and alpha-chaconine, based on the chemiluminescent reaction of tris(2,2'-bipyridine)ruthenium(III) has been developed. The calibration graph was linear in the range of 5 ng/ml-10 microg/ml for both alpha-solanine and alpha-chaconine. The detection limits of alpha-solanine and alpha-chaconine were 1.

Simultaneous detection of monoethanolamine, diethanolamine, and triethanolamine by HPLC with a chemiluminescence reaction and online derivatization to tertiary amine.

In this paper we propose a new postcolumn detection method for compounds having primary, secondary, and tertiary amine moieties. The primary and secondary amine are delivatized by a reaction with epichlorohydrin having an epoxy moiety in a reaction coil to yield a tertiary amine with subsequent chemiluminescence detection using [Ru(bpy)3]3+. The liner values of the calibration curves of monoethanolamine (MEA), diethanolamine (DEA) and triethanolamine (TEA) were 0.

Simultaneous determination of nitrite, nitrate, thiocyanate and uric acid in human saliva by capillary zone electrophoresis and its application to the study of daily variations.

Simultaneous determination of nitrite (NO2-), nitrate (NO3-), thiocyanate (SCN-) and uric acid in human saliva was performed by capillary zone electrophoresis using a coated capillary with reversed electroosmotic flow (EOF), using a 100 mM sodium phosphate buffer at pH 6.5 as a running buffer. Saliva samples were deproteinized with acetonitrile and filtered through a membrane filter.

Simultaneous determination of nitrate and nitrite in biological fluids by capillary electrophoresis and preliminary study on their determination by microchip capillary electrophoresis.

In order to develop a highly sensitive and high-throughput screening method for nitrogen monoxide metabolites in biological fluids, we have investigated the simultaneous determination of nitrite and nitrate, using capillary electrophoresis and microchip capillary electrophoresis. In capillary zone electrophoresis, a running buffer based on human serum components with high ionic strength has been developed for the determination of nitrite and nitrate in human serum and human saliva. We obtained successful separation of nitrite and nitrate in the serum and the saliva within 7 min under optimum analytical conditions.

Sensitive determination of domoic acid using high-performance liquid chromatography with electrogenerated tris(2,2'-bipyridine)ruthenium(III) chemiluminescence detection.

A new sensitive determination method of domoic acid based on the chemiluminescent reaction of tris(2,2'-bipyridine)ruthenium(III) has been developed. The method exhibited good reproducibility. The relative standard deviation of six replicate measurements was 1.

Development of a novel running buffer for the simultaneous determination of nitrate and nitrite in human serum by capillary zone electrophoresis.

In order to improve NO2- peak height and obtain a convenient buffer system for the assay of nitrogen monooxide metabolites, we developed a novel running buffer for the simultaneous determination of nitrite and nitrate in human serum by capillary electrophoresis. The addition of cetyltrimethylammonium chloride to the running buffer resulted in high-speed separation using reverse electroosmotic flow. Highly sensitive determination was also achieved using stacking with 10-fold diluted sample solutions.