High sensitivity flow-based analysis system using a semiconductor laser and thin long flow-through cell for the determination of total phosphorus in water

A highly sensitive detection system using a semiconductor laser (SCL) and a thin long flow-through cell (TLFCT) to match flow-based analysis, such as flow injection analysis (FIA), has been developed. The SCL was a GaAlAs semiconductor laser emitting at 780 nm (5 mW), and the TLFTC, which has a 100 mm thin long light path, was made of a poly(tetrafluoroethylene) (PTFE) rod. The sensitivity was essentially improved about 10-fold in comparison to usual FIA-spectrophotometry using a 10 mm conventional flow cell. When this detection system was applied to the determination of total phosphorus (P) in water by molybdenum-blue spectrophotometry, the relative standard deviation, detection limit and linear range were 1.0% (n = 10 at 20 mug P 1(-1)), 0.6 (3 sigma) and 1.0-50 mug P 1(-1), respectively, and the results for the samples were fairly consistent with those by the official method. It may also be possible to apply the present detection system to other flow-based analytical methods such as the liquid chromatography family.     

One-step preparation of highly concentrated well-stable gold colloids by direct mix of polyelectrolyte and HAuCl4 aqueous solutions at room temperature

Highly concentrated, well-stable gold colloids can be prepared directly from an amine-bearing polyelectrolyte-HAuCl4 aqueous solution at room temperature. It is found that increasing molar ratio of polyelectrolyte to gold leads to increasing particle size. UV-vis spectra, transmission electron microscopy (TEM), and X-ray photoelectron spectra (XPS) were used to characterize the products thus formed.     

Highly regioselective rearrangement of 2-substituted vinylepoxides catalyzed by gallium(III) triflate

Gallium(III) triflate catalyzed the rearrangement of 2-substituted vinylepoxides into beta,gamma-unsaturated carbonyl compounds with high regio- and chemoselectivity (>97/3) in low catalyst loading (1-5 mol %). The alkyl-substituted trimethylsilylvinyl epoxides gave beta,gamma-unsaturated ketone, but aryl-substituted vinylepoxides gave the aldehydes instead.     

NMR determination of absolute site-specific natural isotope ratios of hydrogen in organic molecules. Analytical and mechanistic applications

It has been shown that the “internal” isotope distribution within a given molecular species at the natural abundance level is accessible by a new method, SNIF-NMR, which is based on deuterium NMR. Relative internal factors, R_i/j,have been defined which enable the isotope content of a given site, i, to be compared to that of another molecular site, j, taken as the reference. Several referencing methods intended to provide direct access to relative $\text{externals}$, T_i , and $\text{absolute}$, (D/H)_i , site-specific parameters, are now discussed from both the theoretical and the experimental points of view. In the $\text{intramolecular referencing method}$, which involves a time-consuming chemical transformation of the sample, the risk exists of more or leas systematic errors resulting from discriminating fractionation effects. However this technique offers, conversely, an interesting way of investigating kinetic isotope effects without the need for specific labelling. In spite of its lower spectral precision the $\text{external referencing method}$ has the advantage of being fast and less sensitive to systematic errois and may be used for direct rough routine determinations of the site-specific isotope contents. More precise results can be obtained, at the price of contaminating the sample, when an $\text{intermolecular reference}$ is added and signal heights are used, remembering however that the intensity parameters then have no strict physical meaning in terms of absolute isotope contents. The site-specific parameters, T_i and (D/H)_i thus accessible, provide new information on the mechanisms of the fractionation effects occurring in natural conditions and examples are considered.     

Novel one-dimensional tubelike and two-dimensional polycatenated metal-organic frameworks

Two novel metal-organic frameworks (MOFs) [Zn(TITMB)(OAc)](OH).8.5H(2)O (1) and [Ag(TITMB)N(3)].H(2)O (2) [TITMB = 1,3,5-tris(imidazol-1-ylmethyl)-2,4,6-trimethylbenzene, OAc = acetate anion] were synthesized and their structures were determined by X-ray crystallography. Complex 1 crystallizes in tetragonal space group P(-)4 with a = 23.2664(7) and c = 11.9890(3) A and Z = 8. 1 has a one-dimensional tubelike structure with large inner pore size of approximately 17 A. Complex 2 crystallizes in monoclinic space group C2 with a = 20.7193(10), b = 11.5677(8), and c = 12.2944(6) A, beta = 125.5770(10) degrees, and Z = 4. 2 consists of two-dimensional honeycomb networks that interpenetrate each other to generate a polycatenated structure. In these two complexes, both zinc(II) and silver(I) atoms are four-coordinated with the same tetrahedral coordination geometry. The topologies of 1 and 2 are predominated by the conformations of TITMB, which are cis, trans, trans in 1 and cis, cis, cis in 2, respectively.     

Use of p-dimethylaminobenzalhyde as a colored reagent for determination of procaine hydrochloride by spectrophotometry

Spectrophotometric determination of procaine hydrochloride is described. The procaine hydrochloride reacts with p-dimethylaminobenzalhyde in glacial acetic acid to form an Schiff base which is a yellow compound, and its maximum absorption wavelength is at 455nm, ₄₅₅=3.46×10⁴. The absorbance for procaine hydrochloride from 0.2 to 15 μg ml⁻¹ obeys Beer's law. The linear regression equation of the calibration graph is C=5.866A−0.02, with a linear regression correlative coefficient is 0.9994 and relative standard deviation (RSD) of 1.7%; the detection limit is 0.1 μg ml⁻¹; recovery is from 92.0 to 110.0%. Effects of reaction medium, temperature, gentamycin, beneylpenicillin, kanamycin, streptomycin, foreign ions, and stand for time on the determination of procaine hydrochloride have been examined. The results obtained by this method agreed with those by the official method (dead-stop titration). This method is rapid and simple, and can be used for the determination of procaine hydrochloride in injection solution of procaine hydrochloride.     

Synthesis of four diastereomeric 3,5-dialkoxy-2,4-dimethylalkanals by a simple extension of the non-aldol aldol process to bis(propionates)

[formula: see text] The synthesis of all four diastereomers of bis(propionates), 3,5-dialkoxy-2,4-dimethylalkanals, by non-aldol aldol chemistry is described. The epoxy alcohols (3, 4) were converted into the mesylates (9, 11) which were cleanly rearranged to the desired 3,5-bis(oxygenated)-2,4-dimethylalkanals (10, 12) in high yield. The epoxy mesylates (13, 16) gave the desired products (14, 17) in good yield on treatment with TMSOTf and a hindered base.