Simultaneous determination of serotonin and 5-hydroxyindole-3-acetic acid in human urine by automated precolumn derivatization and semi-microbore column liquid chromatography with fluorescence detection.

An improved high-performance liquid-chromatographic (HPLC) assay for the simultaneous determination of serotonin (5-HT) and 5-hydroxyindole-3-acetic acid (5-HIAA) in human urine is reported. Following the automated precolumn derivatization of urinary 5-HT and 5-HIAA with benzylamine, the derivatives are separated by isocratic elution on a reversed-phase C18 semi-microbore column, and are fluorometrically detected at an excitation wavelength of 345 nm and an emission wavelength of 480 nm. The detection limits of 5-HT and 5-HIAA are 7 and 5 nmol/l in urine (0.7 and 0.5 fmol/20-microl injection). The proposed automatic method permits a highly selective and sensitive determination of 5-HT and 5-HIAA in human urine without any sample purification.     

Scalar curvature of spheres

Financial support from the FRD is gratefully acknowledged     

Phase transitions of lanthanide monophosphides with NaCl-type structure at high pressures

Lanthanide monophosphides LnP (Ln = La, Ce, Pr, Nd, Sm, Gd, Tb, Tm and Yb) with a NaCl-type structure have systematically been prepared at high temperatures. Using synchrotron radiation, X-ray diffractions of LnP have been studied up to 61 GPa at room temperature. The NaCl---CsCl transition for CeP is found at around 25 GPa. First-order phase transitions of LnP (Ln = La, Pr and Nd) with the crystallographic change occur at around 24, 26 and 30 GPa, respectively. The structure of the high pressure phases of these phosphides is a body center tetragonal structure (Ln: 0, 0, 0; P: 1/2, 1/2, 1/2; space group P4/mmm), which can be seen as the distorted CsCl-type structure. The Pr---P distance in the high pressure form of PrP is 2.789 Å. This almost agrees with the sum of covalent radii of Pr and P. The Pr---P bond has the covalent character at very high pressures. Similar results are also obtained for LaP and NdP. The pressure-induced phase transitions of SmP, GdP, TbP, TmP and YbP occur at around 35, 40, 38, 53 and 51 GPa, respectively. The structure of the high pressure phase is unknown. The phase transitions of LnP with many f-electrons are not due to the mechanism of the ordinary NaCl---CsCl transition. The transition pressures of LnP increase with decreasing the lattice constants in the NaCl-type structure, which decrease with increasing atomic number of the lanthanide atoms.     

Synthesis of well‐defined syndiotactic poly(methyl methacrylate) with low‐temperature atom transfer radical polymerization in fluoroalcohol

The copper‐mediated atom transfer radical polymerization of methyl methacrylate (MMA) in 1,1,1,3,3,3‐hexafluoro‐2‐propanol (HFIP) was studied to simultaneously control the molecular weight and tacticity. The polymerization using tris[2‐(dimethylamino)ethyl]amine (Me₆TREN) as a ligand was performed even at ?78°C with a number‐average molecular weight (M_n) of 13,400 and a polydispersity (weight‐average molecular weight/number‐average molecular weight) of 1.31, although the measured M_n's were much higher than the theoretical ones. The addition of copper(II) bromide (CuBr₂) apparently affected the early stage of the polymerization; that is, the polymerization could proceed in a controlled manner under the condition of [MMA]₀/[methyl α‐bromoisobutyrate]₀/[CuBr]₀/[CuBr₂]₀/[Me₆TREN]₀ = 200/1/1/0.2/1.2 at ?20°C with an MMA/HFIP ratio of 1/4 (v/v). For the field desorption mass spectrum of Cu^IBr/Me₆TREN in HFIP, there were [Cu(Me₆TREN)Br]⁺ and [Cu(Me₆TREN)OCH(CF₃)₂]⁺, indicating that HFIP should coordinate to the Cu^I/Me₆TREN complex. The syndiotacticity of the obtained poly(methyl methacrylate)s increased with the decreasing polymerization temperature; the racemo content was 84% for ?78°C, 77% for ?30°C, 75% for ?20°C, and 63% for 30°C. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1436–1446, 2006     

Effects of quaternary ammonium bases on valence-saturated but coordination-unsaturated chelates: Part IV. Extraction of some divalent metal 8-hydroxyquinolinates

The effect of zephiramine on the chelate formation and extraction of some divalent metals with oxine is reported. In the presence of zephiramine, the non-extractable 1:2 zinc— and cadmium—oxine chelates as well as the extractable 1:2 nickel— and manganese—oxine chelates become highly coordinated ternary complexes, M(Q)₃ (zeph), which are easily extracted into 1,2-dichloroethane. Copper is easily extracted into 1,2-dichloroethane as Cu(Q)₂, which is not affected by zephiramine.     

Cyclopolymerization of diallylamine derivatives in dimethyl sulfoxide

Diallyl quaternary ammonium chlorides, bromides and N-alkyldiallylamine hydrochlorides were polymerized with ammonium persulfate (APS) in dimethyl sulfoxide (DMSO). The dependences of yield and molecular weight of polymers on polymerization conditions were examined and quaternary ammonium chlorides were found to have better polymerizability than bromides. The poly(diallyl quaternary ammonium chlorides) obtained with APS—DMSO system are expected to have quite high molecular weights, as determined from the measurement of limiting viscosity numbers of the polymers in NaCl aqueous solution.     

Polymers having stable radicals. II. Synthesis of nitroxyl polymers from 4-methacryloyl derivatives of 1-hydroxy-2,2,6,6-tetramethylpiperidine

Polymers having stable pendant . radicals were synthesized through their precursor polymers by oxidizing them in air or by H₂O₂–Na₂WO₄. Hydrochlorides and sulfates of 4-methacryloylamino- and 4-methacryloyloxy-1-hydroxy-2,2,6,6-tetramethylpiperidines were synthesized as precursor monomers and polymerized by using α,α′-azobisisobutyronitrile under appropriate conditions to precursor polymers of high molecular weight: poly-4-methacryloylamino-/oxy-1-hydroxy-2,2,6,6-tetramethylpiperidinehydrochlorides and sulfates. The precursor polymers were converted to polymers having nitroxyl stable radicals, i.e., poly-4-methacryloylamino-/oxy-2,2,6,6-tetramethylpiperidine-1-oxyls, by oxidation in air or with H₂O₂–Na₂WO₄ without any main-chain scission. The structure of the resultant stable radical polymers was determined by infrared, ultraviolet, and ESR spectroscopy. Based on the results of spectroscopic analysis and Kjeldahl analysis, the transformation from precursors to nitroxyl stable radical polymers was found to be quantitative. Investigations on the applicability of polymeric nitroxyl radicals to oxidation-reduction reactions were attempted by means of polarography; the reduction half-wave potential was found to be ?1.16 V for the mercury pool.