Large-volume injection electrothermal AAS combined with tungsten-treated pyrolytic graphite furnace: determination of cadmium in tap, snow and river water samples with phosphate modifier.

A large-volume (100 microl) injection-ETAAS with W-treated PG furnace combined with a phosphate modifier was applied to the determination of unpolluted levels of Cd in tap, snow and river-water samples. The limit of detection of 1.1 ng l(-1) was observed for a 4 w/v% NH4H2PO4 modifer. Matrix interference studies were tested for major ion species well found in fresh water. The direct determination of Cd in certified river water (12 +/- 2 ng l(-1)) was carried out and the observed value was in agreement with the certified one. The good recoveries of Cd added to real environmental water samples were also observed. This method was applied to the determination of Cd in unpolluted environmental water samples.     

Improved detectability with a polymer-based trapping device in rapid HPLC analysis for ultra-low levels of bisphenol A (BPA) in environmental samples.

A new high-performance liquid chromatography (HPLC) method has been developed to detect ultra-low concentrations of bisphenol-A (BPA) (below 1 ng/L (ppt)) using column switching electrochemical detection (ECD). The results were superior to those obtained from manual pretreatment procedure with membrane stationary phase. BPA is inherently ubiquitous in the environment, including tools and solvents used for its analysis; to obtain meaningful results, therefore, the concentration of the overall BPA contamination must be below the detection limit for BPA using the analytical system. Therefore, purified water for preparing the standard BPA solution must be filtered with a hydrophobic membrane to suppress BPA background levels of contamination. In addition, we investigated methods for effectively preserving environmental water containing BPA. The addition of a small amount of ethylenediaminetetraacetic acid (EDTA) provided good recovery even after overnight storage. By employing these precautionary measures and procedures to reduce BPA contamination from the analytical procedure, we could accurately determine l(-10) ppt of BPA in environmental water samples using a column switching HPLC system.     

The Canonical Solutions of the Q-Systems¶ and the Kirillov–Reshetikhin Conjecture

We study a class of systems of functional equations closely related to various kinds of integrable statistical and quantum mechanical models. We call them the finite and infinite $Q$-systems according to the number of functions and equations. The finite Q-systems appear as the thermal equilibrium conditions (the Sutherland–Wu equation) for certain statistical mechanical systems. Some infinite Q-systems appear as the relations of the normalized characters of the KR modules of the Yangians and the quantum affine algebras. We give two types of power series formulae for the unique solution (resp. the unique canonical solution) for a finite (resp. infinite) Q-system. As an application, we reformulate the Kirillov–Reshetikhin conjecture on the multiplicities formula of the KR modules in terms of the canonical solutions of Q-systems. Received: 2 August 2001 / Accepted: 27 December 2001     

Preparation and certification of the new reference materials; plastics (disk form, JSAC 0621-0625) for determination of mercury using x-ray fluorescent analysis.

The Japan Society for Analytical Chemistry has developed some new plastic certified reference materials (CRMs) for the analysis of mercury in polyester disks using XRF analysis. These CRMs (named as JSAC 0621-0625) were prepared by casting polyesters including a toluene solution of organometallic compounds as a standard. Concentrations of the five levels of mercury ranged from 0 to 250 mg/kg. Homogeneity tests of prepared disks had shown excellent results. Interlaboratory comparison study for the certification was performed by 15 laboratory participants. The z-scores in robust statistical method was applied for the evaluation of outliers. The certified values were assigned after discarding outliers. The uncertainties of certified values were determined as the confidence levels of 95%.     

Synthesis of aromatic polyamides by 1-hydroxybenzotriazole-catalyzed polycondensation of active aromatic diesters with aromatic diamines

Catalytic actions of various additives were studied in the polycondensation of di(4-nitrophenyl) isophthalate with bis(4-aminophenyl) ether in N-methyl-2-pyrrolidone, and 1-hydroxybenzotriazole (HOBt) was found to be a highly effective catalyst that yielded high-molecular-weight polyamide. In addition to the polycondensation of the 4-nitrophenyl ester, the polymerization of negatively substituted phenyl esters like di(2,4,5-trichlorophenyl) isophthalate was also accelerated by HOBt. For the HOBt-catalyzed aminolysis of esters a bifunctional concerted mechanism that involves an eight-membered transition state was proposed.     

Dianion of sulfinylacetone as a synthetic equivalent of beta-enolate of propionic acid: a novel synthesis of carboxylic acids from alkyl halides with three-carbon elongation

The reaction of the dianion of phenylsulfinylacetone with alkyl halides afforded beta-keto sulfoxides, which were first chlorinated with hexachloroethane and then treated successively with KH and t-BuLi to give carboxylic acids in three-steps in moderate overall yields from the alkyl halides. This procedure affords a good method for a synthesis of carboxylic acids from alkyl halides with three-carbon elongation.     

Structural variety of membrane permeable peptides

Peptide-mediated protein delivery into living cells has been attracting our attention. Among the peptides that have been reported to have carrier activity, the one from the human immunodeficient virus (HIV)-1 Tat has been most often used for the introduction of exogenous macromolecules into cells. We have shown that not only the Tat peptide, but also various arginine-rich peptides showed very similar characteristics in translocation, and the possible presence of ubiquitous internalization mechanisms among the arginine-rich peptides has also been suggested. These arginine-rich peptides includes ones derived from HIV-1 Rev and flock house virus coat proteins. The linear- and branched-chain peptides containing approximately 8 residues of arginine also show a similar ability. In this review, we present the structural variety of membrane permeable peptides and provide a survey of the findings on the translocation of these peptides through the cell membranes.     

Automatic semi-microcolumn liquid chromatographic determination of catecholamines in rat plasma utilizing peroxyoxalate chemiluminescence reaction

A fully automated and highly sensitive method with a semi-microcolumn liquid chromatography system for the determination of rat plasma catecholamines (CAs) was developed. Automated on-line extraction of CAs in diluted plasma using a precolumn packed with strong acidic cation exchange resin was coupled with separation of CAs on a semi-microcolumn (250 x 1.5 mm id). fluorogenic derivatization with ethylenediamine and finally postcolumn peroxyoxalate chemiluminescence detection utilizing bis[2-(3,6,9-trioxadecanyloxycarbonyl)-4-nitrophenyl]oxalate (TDPO) and hydrogen peroxide. The detection limits were 0.91, 0.36 and 1.1 fmol for norepinephrine (noradrenaline), epinephrine (adrenaline) and dopamine, respectively, at a signal-to-noise ratio of 3. A good linearity of the calibration curve for each CA was observed in the range of 5.0 to 500 fmol for each CA using N-methyldopamine (N-MeDA) as an internal standard. The RSD for the proposed method (n = 5) were 3.7-9.5% for the intra-day assay and 6.6-10.0% for the inter-day assay. The volume of rat plasma required for the determination of CAs was 10 microliters.     

Preparation and properties of polyamides and polymides containing bibenzyl,stilbene, and tolan structures

Polyisophthalamides and polyterephthalamides were prepared by the solution polycondensation of the corresponding diacyl chlorides with 4,4′-diaminobibenzyl, trans-4,4′-diaminostilbene, and 4,4′-diaminotolan in N,N-dimethylacetamide (DMAc). Polypyromellitimides were synthesized in two steps by the ring-opening polyaddition of pyromellitic dianhydride with the aromatic diamines in DMAc, followed by thermal cyclodehydration. The amorphous polyisophthalamides were soluble in some amide solvents containing lithium chloride, while the polyterephthalamides having fair degree of crystallinity were insoluble in these solvents. The thermal stability of these aromatic polymers decreased in the order of the tolan-containing polymers > the stilbene-containing polymers > the bibenzyl-containing polymers, both in air and under nitrogen.