Colorimetric and fluorometric determination of uric acid by a suspension-based assay using enzyme-immobilized micro-sized particles.

Daily monitoring of serum uric acid levels is very important to provide appropriate treatment according to the constitution and lifestyle of individual hyperuricemic patients. We have developed a suspension-based assay to measure uric acid by adding a sample solution to the suspension containing micro-sized particles immobilized on uricase and horseradish peroxidase (HRP). In the proposed method, the mediator reaction of uricase, HRP, and uric acid produces resorufin from Amplex red.

Hydrophilic interaction chromatography-type sorbent prepared by the modification of methacrylate-base resin with polyethyleneimine for solid-phase extraction of polar compounds.

Hydrophilic interaction chromatography (HILIC)-type sorbents were newly developed for the solid-phase extraction (SPE) of polar compounds. Two methacrylate-base resins with different cross-linking monomers and pore properties were synthesized, and three polyethyleneimines (PEIs) with different molecular weights were modified onto each base resin. In both cases, PEIs with a molecular weight of 10,000 (PEI-10,000) exhibited the highest adsorption properties for polar compounds (uracil, uridine, adenosine, cytidine, and guanosine).

Novel chemically cross-linked self-molding particulate sorbents as solid-phase extraction media.

Here, we describe novel, chemically cross-linked, self-molding particulate polymer sorbents that are utilized as a molding-type solid-phase extraction medium (M-SPEM), which exhibits high permeability and rigidness. To fabricate such M-SPEM, first, polyethyleneimine (PEI)-modified reversed-phase (RP)-type particulate sorbents were synthesized, thereafter, they were chemically cross-linked by a polymer having many epoxy groups together with additional PEI. By optimizing the binding conditions of the particulate sorbents, the resultant M-SPEM has almost the same adsorption properties as the corresponding unmolded particulate sorbent for some polar (e.

Preparation and evaluation of molding-type solid-phase extraction media binding with commercially available adhesives.

A fabrication method of molding-type solid-phase extraction media (M-SPEM) bound with commercially available adhesive is presented. Six pieces of M-SPEM were prepared by heating each kneaded product of a particulate sorbent and an adhesive inserted into a six-hole cylindrical mold for hardening under an open system and normal pressure. The particulate sorbent contained in M-SPEM was divinylbenzene-based reversed-phase mode solid-phase extractants that we have reported.

Development of a fluorescence microplate reader using an organic photodiode array with a large light receiving area.

We developed a small fluorescence microplate reader with an organic photodiode (OPD) array. The OPD array has nine OPDs that have a large light receiving area (9.62 mm per one OPD).

Lead Assays with Smartphone Detection Using a Monolithic Rod with 4-(2-Pyridylazo) Resorcinol.

A monolithic rod of polyurethane foam-[4-(2-pyridylazo) resorcinol] (PUF-PAR) as a simple chemical sensor for lead assays with smartphone detection and image processing was developed. With readily available simple apparatus such as a plastic cup and a stirrer rod, the monolithic PUF rod was synthesized in a glass tube. The monolithic PUF-PAR rod could be directly loaded by standard/sample solution without sample preparation.

Determination of Lead Employing Simple Flow Injection AAS with Monolithic Alginate-Polyurethane Composite Packed In-Valve Column.

A simple flow injection FlameAAS for lead determination with an alginate-polyurethane composite (ALG-PUC) monolithic in-valve column has been developed. The ALG-PUC monolithic rod was prepared by mixing methylene diphenyl diisocyanate with polyol and sodium alginate with the ratio of 2:1:1 by weight for a 5 min polymerization reaction. It was then put into a column (0.

Development and Evaluation of HILIC-type Sorbents Modified with Hydrophilic Copolymers for Solid-phase Extraction.

Hydrophilic interaction chromatography (HILIC) has attractive attention for the separation of water-soluble compounds via HPLC. There are, however, few studies on the pretreatment of the HILIC-type solid-phase extraction (SPE) due to the difficulty of obtaining the HILIC-type sorbent. Therefore, the development of HILIC-type sorbents for SPE is essential.

Molding-type Solid-phase Extraction Media Glued with Commercially Available Adhesives.

The handling of a particulate sorbent for solid-phase extraction is often troublesome because it causes static clinging and scattering. To overcome this problem, a production method for a simple molding-type solid-phase extraction medium (M-SPEM) was developed in this study by using commercially available adhesives. The content of a particulate sorbent can increase to as much as 85 wt% in the M-SPEM.

Evaluation of the adsorption properties of nucleobase-modified sorbents for a solid-phase extraction of water-soluble compounds.

We developed hydrophilic interaction chromatography (HILIC)-type sorbents modified with nucleobases for solid phase extraction (SPE). The synthesized hydrophilic base resins were modified by each nucleobase (adenine, guanine, and cytosine). The measurement of the amount of water content indicated that each nucleobase-modified sorbent had a water layer.

Preparation of N-Ethyl-2'-deoxyguanosine-d as an Internal Standard for the Electrospray Ionization-Tandem Mass Spectrometric Determination of DNA Damage by Acetaldehyde.

The deuteration of N-ethyl-2'-deoxyguanosine (Et-dG), which is a DNA adduct generated from acetaldehyde, was studied by the addition reaction of acetaldehyde-d to 2'-deoxyguanosine (dG) in deuterium oxide (DO), with the aim to obtain an isotope internal standard for the liquid chromatography/tandem mass spectrometry (LC/MS/MS) quantitation of Et-dG. The replacement of the dG C-8 hydrogen atom by a deuteron atom took place at 50°C in DO and afforded a mixture of Et-dG-d and Et-dG-d. Et-dG-d, which was stable in aqueous solutions, was prepared by incubating the mixture in HO at 60°C for 48 h.

Preparation of Cyclic-1,N-propano-2'-deoxyguanosine-d as an Internal Standard for ESI-MS/MS Determination of DNA Damage from Acetaldehyde.

Cyclic-1,N-propano-2'-deoxyguanosine-d (CPr-dG-d) was prepared as an isotopic internal standard (IS) for electrospray ionization tandem mass spectrometry (ESI-MS/MS) quantification of CPr-dG in DNA as a candidate cancer risk marker of acetaldehyde intake, mainly from drinking. The deuterated compound was reasonably synthesized from acetaldehyde-d and 2'-deoxyguanosine in deuterium oxide (DO), preventing the deuterium atoms of acetaldehyde-d from being substituted by hydrogen atoms, which occurred seriously in aqueous synthesis media via keto-enol tautomerism. Furthermore, another deuterium atom was added from DO to form CPr-dG-d.

Optimization of background electrolyte composition for simultaneous contactless conductivity and fluorescence detection in capillary electrophoresis of biological samples.

In this article, optimization of BGE for simultaneous separation of inorganic ions, organic acids, and glutathione using dual C D-LIF detection in capillary electrophoresis is presented. The optimized BGE consisted of 30 mM 2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid, 15 mM 2-amino-2-hydroxymethyl-propane-1,3-diol, and 2 mM 18-crown-6 at pH 7.2 and allowed simultaneous separation of ten inorganic anions and cations, three organic acids and glutathione in 20 min.

Effects of pendant-like hydrophilic monomers on the adsorption properties of reversed-phase-type sorbents for solid-phase extraction.

Solid-phase extraction (SPE) has been extensively employed as a pretreatment method. In SPE, reversed-phase-type sorbents have been widely applied for the pretreatment of environmental or biological samples. Hydrophilic-lipophilic balance (HLB)-type sorbents, constituting the copolymers used as reversed-phase-type sorbents, have been applied for various sample pretreatment methods.

Evaluation of Type-A Endonucleases for the Quantitative Analysis of DNA Damage due to Exposure to Acetaldehyde Using Capillary Electrophoresis.

The substrate selectivities of three endonucleases were studied quantitatively using capillary zone electrophoresis to find one giving N-ethyl(Et)-2'-deoxyguanosine-5'-monophosphate (5'-dGMP) and cyclic 1,N-propano(CPr)-5'-dGMP from DNAs damaged by acetaldehyde (AA). Six 2'-deoxyribonucleoside-5'-monophosphates to be quantified in the hydrolysis solutions of DNAs, namely, Et-5'-dGMP, CPr-5'-dGMP, and four authentic ones, were completely separated using a 100 mM borate running buffer solution having an optimized pH of 9.67.

Effects of hydrophilic monomers on sorptive properties of divinylbenzene-based reversed phase sorbents.

Solid phase extraction (SPE) has been extensively used as a pretreatment method. In SPE methods, commercially available reversed phase type sorbents, which consist of macroporus styrene-divinylbenzene or copolymers including divinylbenzene (DVB) and hydrophilic monomers, have been applied to a variety of samples. The later sorbents are called hydrophilic lipophilic balanced (HLB) type sorbents.

Progress in a selective method for the determination of the acetaldehyde-derived DNA adducts by using HILIC-ESI-MS/MS.

Acetaldehyde (AA), which is present in tobacco smoke, automobile exhaust gases and alcohol beverage, is a mutagen and carcinogen. AA reacts with 2'-deoxyguanosine (dG) in DNA to form N-ethyl-dG (EtdG) and cyclic, 1, N-propano-dG (CPrdG), which are considered to have a critical role in carcinogenesis induced by AA. In this study, we have developed a highly sensitive method for the quantitation of the two AA-derived DNA adducts by using liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) in which hydrophilic interaction chromatography (HILIC) employing mobile phases of high organic solvent concentration was selected to improve the ionization efficiency in the ESI process.

Simple Pretreatment and HILIC Separation for LC-ESI-MS/MS Determination of Adenosine in Human Plasma.

A simple pretreatment method and separation mode for the LC-ESI-MS/MS determination of adenosine in human plasma have been developed. Deproteinization by acetonitrile and ultrafiltration followed by chromatographic separation with a hydrophilic interaction chromatographic (HILIC) column give a highly sensitive MS/MS response without ionic suppression caused by the matrix compounds in human plasma. In addition, the presence of ammonium acetate in the mobile phase contributes to high sensitivity in MS/MS detection, facilitating the ionization of adenosine.

Advanced Stopped-in-Loop Flow Analysis with a Reagents-Merging Zones Technique for a Catalytic Successive Determination of Vanadium and Iron.

An advanced stopped-in-loop flow analysis (SILFA) is proposed for the catalytic determinations of vanadium and iron. The chemistry relies on a vanadium- or iron-catalyzed oxidative reaction of p-anisidine by bromate or hydrogen peroxide in the presence of an activator (Tiron or 1,10-phenanthlorine) to form a red dye (510 nm). Reagents for the vanadium- or iron-catalyzed reaction are well mixed by a reagents-merging zones technique.

Stopped-in-loop flow analysis system for successive determination of trace vanadium and iron in drinking water using their catalytic reactions.

An automated stopped-in-loop flow analysis (SILFA) system is proposed for the successive catalytic determination of vanadium and iron. The determination of vanadium was based on the p-anisidine oxidation by potassium bromate in the presence of Tiron as an activator to form a reddish dye, which has an absorption maximum at 510 nm. The selectivity of the vanadium determination was greatly improved by adding diphosphate as a masking agent of iron.

Automatic On-line Solid-phase Extraction-Electrothermal Atomic Absorption Spectrometry Exploiting Sequential Injection Analysis for Trace Vanadium, Cadmium and Lead Determination in Human Urine Samples.

A fully automated sequential injection column preconcentration method for the on-line determination of trace vanadium, cadmium and lead in urine samples was successfully developed, utilizing electrothermal atomic absorption spectrometry (ETAAS). Polyamino-polycarboxylic acid chelating resin (Nobias chelate PA-1) packed into a handmade minicolumn was used as a sorbent material. Effective on-line retention of chelate complexes of analytes was achieved at pH 6.

Stepwise elusion method in micellar electrokinetic chromatography via sequential use of lithium perfluorooctadecyl sulfonate and lithium dodecyl sulfate.

An effective stepwise micellar electrokinetic chromatography (MEKC) elution method was developed using lithium perfluorooctadecyl sulfonate (LPFOS) and lithium dodecyl sulfate (LDS). The hydrogen-bonding property of LPFOS micelles differs from that of LDS micelles, which leads to remarkably different selectivity in the transfer of solutes to the micelles. The present stepwise method is performed by replacing the inlet reservoir of a first running solution containing LPFOS with that of a second running solution containing LDS during a single separation run in the absence of electroosmotic flow under acidic conditions, where LPFOS micelles work as carriers in first and then LDS micelles turn over.

Facile and effective pretreatment using stop and go extraction tips for LC-MS/MS analysis of trace amounts of DNA adducts.

The preparation and application of a stop and go extraction tip (StageTip) used for pre-purification of sample solutions for LC-MS/MS analysis of DNA adducts was simplified and improved to increase throughput while maintaining high adduct selectivity. It was demonstrated that the StageTip composed of two sheets of a poly(styrene-divinylbenzene) copolymer disk could be easily prepared and proved useful for selective extraction of trace amounts of DNA adducts from a sample solution containing a great quantity of normal deoxynucleosides.

Tracking the growth of tadpole-shaped aggregates by scanning electron microscopy.

A single-step strategy has been developed toward the synthesis of micrometer-sized, tadpole-like structures comprising a repeating sequence of a three-dimensional gold nanoparticle (AuNP)-aniline polymer-AuNP arrangement. The size and shape of the microstructure strongly depends on the concentration of aniline in the reaction solution. Herein, we describe the formation mechanism of the microstructure by focusing on the surface morphology.