Solubilities of rare earth lodates in aqueous and aqueous alcoholic solvent mixtures

The solubilities of thirteen iodates of rare earth metals in aqueous and aqueous alcoholic solvent mixtures at 25°C were measured. Methanol and ethanol were used as the alcoholic components, and the alcohol concentrations in solvent mixtures were between 0–40 mass percent. From the solubilities measured in this study and the published data, the recommended solubility values of eleven iodates of rare earth metals [Ln(IO₃)₃: Ln=Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb] in water at 25°C were decided by applying the guidelines of the IUPAC Solubility Data Project, and the solubilities of two iodates [Ln(IO₃)₃: Ce and Lu] are designated as tentative values. The change in solubility of lanthanide iodates in aqueous and aqueous alcoholic solvent mixtures as a function of lanthanide atomic number is discussed. The logarithm of the solubility decreases almost linearly with the reciprocal of the dielectric constant of the solvent mixture, as expected from Born's equation and its modifications.Presentation to First International Symposium on Solubility Phenomena, University of Western Ontario, London, Ontario, August 21–23, 1984.     

Total Synthesis of (±)-Hirsutene via Pd-Promoted Cycloalkenylation Reaction

Beginning with trans-2-methyl-4-cyclohexenecarboxylic acid (9), a total synthesis of linear triquinane sesquiterpene (±)-hirsutene (1) has been accomplished. An acid catalyzed intramolecular conjugate addition (7→6a) and a Pd²⁺-promoted highly stereocontrolled cyclization (5→4) were utilized for the key step of the sequence. Interestingly, some synthetic intermediates exhibited cytotoxicity.     

Determination of total 3α-hydroxy bile acids in serum by a bioluminescent flow-injection system using a hollow-fibre reactor

A continuous-flow bioluminescence method for measuring total 3α-hydroxy bile acids in serum is described. A bacterial luciferase and NADH:FMN oxidoreductase are covalently co-immobilized on a CNBr-activated Sepharose 4B. A permeable membrane (hollow fibre) reactor is used for the introduction of NAD⁺ and bioluminescent reagent. The reagent permeates into the flow-stream due to the existing difference in ionic strength. The continuous-flow light-emitting system, in which the column filled with the immobilized bioluminescent enzyme is placed in front of a photomultiplier tube inside a photon counter, is versatile and simple. The technique was tested by comparing results with those obtained by fluorimetry. More than 20 samples an hour can be analyzed. Normal values for total bile acids content serum ranged from 1.0 to 7.5 μM, in agreement with those obtained by the other method. Excellent reproducibility, precision, and sensitivity are achieved.     

Determination of perfluorinated alkyl acid concentrations in human serum and milk standard reference materials

Standard Reference Materials (SRMs) are certified reference materials produced by the National Institute of Standards and Technology that are homogeneous materials well characterized with values for specified properties, such as environmental contaminant concentrations. They can be used to validate measurement methods and are critical in improving data quality. Disagreements in perfluorinated alkyl acid (PFAA) concentrations measured in environmental matrices during past interlaboratory comparisons emphasized the need for SRMs with values assigned for PFAAs. We performed a new interlaboratory comparison among six laboratories and provided, for the first time, value assignment of PFAAs in SRMs. Concentrations for perfluorooctane sulfonate (PFOS), perfluorooctanoate (PFOA), and other PFAAs in two human serum and two human milk SRMs are reported. PFAA concentration measurements agreed for serum SRM 1957 using different analytical methods in six laboratories and for milk SRM 1954 in three laboratories. The interlaboratory relative standard deviation for PFOS in SRM 1957 was 7%, which is an improvement over past interlaboratory studies. Matrix interferences are discussed, as well as temporal trends and the percentage of branched vs. linear isomers. The concentrations in these SRMs are similar to the present-day average concentrations measured in human serum and milk, resulting in representative and useful control materials for PFAA human monitoring studies.     

Hyperfine anomaly arising from the nuclear spin-forbidden transition,and absolute sign determination of the zero-field splitting constant

It has been found in the triplet E.S.R. spectra of radical pairs in irradiated potassium deuterium fumarate that the hyperfine structure of the two transitions, M _s = 1?0 and M _s = 0?+1, are entirely different. This anomaly has been interpreted in terms of the forbidden transition arising from the mixing of the nuclear spin states by the anisotropic hyperfine interaction. The theory has been developed for multiplet electron spin systems and includes the nuclear Zeeman interaction which is often neglected. The theoretical predictions are in good agreement with the observed separations and intensities of the anomalous hyperfine lines. In addition, it has been found that since the forbidden lines of the electron spin multiplet system with S ≥ 1 appear strongly only in transitions which include some specific electronic spin states, the anomalous features of the spectra make it possible to determine the absolute sign of the zero-field or hyperfine splitting constant, if the sign for one of them is known. Using this principle, attempts have been made to determine the absolute sign of the zero-field splitting constant for a number of triplet E.S.R. spectra which exhibit a hyperfine anomaly arising from the proposed mechanism.     

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 0.02 - 1.0 nmol (r2 = 0.9986), 0.02 - 0.5 nmol (r2 = 0.9993) and 0.1 - 1.0 nmol (r2 = 0.9482), respectively. Also, the detection limits (S/N = 3) of MEA, DEA and TEA were 30, 25 and 40 pmol, respectively. The amount of DEA and TEA in shaving cream (60 microg/20 microL) were found to be 0.3 nmol and 14 nmol, respectively, by the proposed method.     

New water-soluble hydrogen donors for the enzymatic spectrophotometric determination of hydrogen peroxide

Eight N -alkyl-N-V-sulphopropylaniline derivatives have been synthesized and assessed as water-soluble hydrogen donors for the spectrophotometric determination of hydrogen peroxide in the presence of peroxidase. The sodium salts of N-ethyl-N-sulphopropylaniline (ALPS), N-ethyl-N-sulphopropyl-m-toluidine (TOPS) and N -ethyl-N-sulphopropyl-m-anisidine (ADPS) are recommended. They have excellent water solubilities, and the optimum pH range for oxidative condensation with 4-aminoantipyrine in the presence of hydrogen peroxide and peroxidase is 5.5–9.5. The absorbances of the resulting chromogens are 2–3 times higher than that achieved with phenol. The molar absorptivities of the chromogens with 4-aminoantipyrine are 41300 (ALPS, λ_max 561 nm), 37400 (TOPS, λ_max 550 nm) and 27900 (ADPS, λ_max 540 nm). Calibration graphs for the determination of hydrogen peroxide in the presence of a control serum are linear for 7–40 × 10^-6 mol H₂O₂ l^-1.     

Photosensitized hydrogen evolution from water using conjugated polymers wrapped in dendrimeric electrolytes

High-efficiency light-driven hydrogen evolution from water was demonstrated by using poly(phenyleneethynylene) bearing negatively charged, [G3] poly(benzyl ether) dendrimeric side groups 3(L4) as photosensitizer. Three-dimensional wrapping of the conjugated backbone suppressed self-quenching of the photoexcited state, while methyl viologen (MV(2+)), a positively charged electron acceptor, was trapped on its negatively charged surface, to form a spatially separated donor-acceptor supramolecular complex. Studies with time-resolved fluorescence spectroscopy showed that the quenching rate constant (k(q) = 1.2 x 10(15) M(-1) s(-1)) is much greater than diffusion control rate constants. Upon excitation of 3(L4) in the presence of a mixture of MV(2+), triethanolamine (TEOA; sacrificial electron donor), and a colloidal PVA-Pt, hydrogen evolution took place with an overall efficiency of 13%, 1 order of magnitude better than precedent examples. Comparative studies with several reference sensitizers showed that spatial isolation of the conjugated backbone and its long-range pi-electronic conjugation, along with electrostatic interactions on the exterior surface, play important roles in achieving the efficient photosensitized water reduction.     

Intercalation of n-Alkylamines and n-Alkyldiamines into γ-Zirconium Phenylphosphonate Phosphate

Crystalline -zirconium phenylphosphonate phosphate was prepared according to Yamanaka's method and the intercalation behavior of n-alkylamines and n-alkyldiamines were investigated. In the case of n-alkylamines, a linear increase in interlayer distance was observed up to a carbon atom number of 12, whereas in n-alkyldiamines, only two di-amines, ethylenediamine and propylenediamine, were intercalated with respective increases in the interlayer distance. The increment of interlayer distance in both monoamines and diamines indicates the formation of a monomolecular layer in the interlayer region of the host, in contrast to the case in -zirconium phosphate as a host.