Concentration and determination of trace organic pollutants in water

Organic pollutants in water are isolated on a mini-sampler tube containing a macroporous resin. The sorbed pollutants are next thermally transferred to a second sorption tube and then to an analytical column where they are separated and determined by temperature-programmed gas chromatography. Excellent recoveries were obtained for tests in which model organic compounds of various classes were added to water. The water sample is much smaller than that required with previous analytical methods.     

Automatic geometry optimization for molecules with d orbitals. I. General analytic formulas for derivatives of slater orbitals

General analytic formulas for derivatives of real Slater orbitals with respect to the Cartesian coordinates x and y have been derived. The application of this result to molecular geometry optimization or to the construction of a force constant matrix is briefly discussed.     

KINETIC STUDIES OF THE TRYPTOPHAN TRIPLET STATE IN SOLID FILM AND IN WOOL KERATIN

Abstract— The triplet state of tryptophan in the solid environments of a polyvinyl alcohol) (PVA) film and the protein wool keratin has been studied by emission and absorption spectroscopy at room temperature. The decay kinetics of the triplet state vary depending on the conditions under which the study is made. The observation of second order kinetics suggests triplet-triplet interactions play a major role in the deactivation of the tryptophan triplet state in PVA films plasticised by the presence of water vapour. For wool keratin in the presence of air the major mechanism appears to be a first order reaction between tryptophan residues and oxygen. The actual effects of moisture and oxygen on the tryptophan triplet state are discussed.     

Micellar catalysis of the reaction of 2,4-dinitrofluorobenzene with phenoxide and thiophenoxide ions

The reactions of 2,4-dinitrofluorobenzene with phenoxide and thiophenoxide ion in water are strongly catalyzed by micelles of cetyltrimethylammonium bromide (CTABr) by factors of 230 and 1100 respectively. Nonionic micelles of Brij weakly catalyze the reaction with thiophenoxide ion. Spectral measurements show that phenoxide, and especially thiophenoxide, ions interact strongly with micelles of CTABr which also markedly change the acid dissociation of phenol under given buffer conditions.     

Regioselectivite sous controle d'interactions de charges ou d'interactions orbitalaires : Reaction d'anions α-chlores a charge localisee ou delocalisee sur des α-enones

Benzalacetophenone reacts with anions derived from methyl chloroacetate and chloroacetonitrile (which are of the charge-localized type) at the carbonyl group to give α-epoxyalkenes. In contrast, the same ketone reacts with the anions derived from methyl phenylchloroacetate and phenylchloroacetonitrile (the negative charge of which is delocalized) to give cyclopropanes by attack at the carbon-carbon double bond. These results support the hypothesis that the reaction is charge-controlled with the former two reagents and orbital-controlled in the case of the latter two. Only one cyclopropane stereoisomer is formed in HMPA.     

Deoxygenation of quinoxaline N-oxides and related compounds

The alkali induced deoxygenation of 3-(α-hydroxyalkyl)-quinoxaline-1-oxides is shown to be first order in substrate and in hydroxide ion. Examples are given to illustrate the synthetic utility of this reaction for the synthesis of quinoxaline and quinoline derivatives of type 4, 5, 8, and 11. The mechanism of the reaction is related to the mechanism of deoxygenation of heteroaromatic N-oxides by sodium dithionite.     

Analysis of 19-norandrosterone in human urine by gas chromatography–isotope-dilution mass spectrometry: method adopted by LGC for participation in the Comité Consultatif pour la Quantité de Matière (CCQM) Pilot Study P68

The method used at LGC for analysis of “total” 19-norandrosterone (19-norandrosterone glucuronide plus “free” 19-norandrosterone) in urine for the Comité Consultatif pour la Quantité de Matière Pilot Study (CCQM-P68) is described. The analytical method used was a modified version of the method developed at the National Measurement Institute of Australia, which used a hydrolysis and derivatisation procedure first described by the German Sports University. This method is routinely used by World Anti-Doping Agency-accredited laboratories for sports drug testing. The main modifications made to the method were the use of 19-norandrosterone glucuronide as a calibration standard and 19-norandrosterone glucuronide-d4 as an isotopically labelled internal standard, and the use of a bench-top quadrupole gas chromatograph–mass spectrometer. The results produced by LGC (2.14 ± 0.15 ng g⁻¹ expanded uncertainty, coverage factor k = 2) were in excellent agreement with those from other participating national metrology institutes and thus further validates the exact-matching isotope-dilution mass spectrometric procedures used at LGC for a wide range of reference measurement applications, including measurement of ng g⁻¹ levels of steroids in a biological matrix.     

Electrophoretically mediated microanalysis with small molecules: the Jaffé method for creatinine carried out in a capillary tube

An eletrophoretically mediated microanalysis (EMMA) approach, used to perform online chemistry between two small molecules, has been characterized and optimized. The "plug-plug" type EMMA method involved electrophoretic mixing and subsequent reaction of nanoliter plugs of creatinine-containing samples and alkaline picrate (Jaffe reaction) within the confines of the capillary column, which acts as a microreactor. Analyses were performed by pressure injecting a plug of picrate followed by a plug of the creatinine-containing sample. A potential was then applied to electrophoretically mix the two reactants, and an incubation time of up to 6 min allowed the reaction to proceed prior to the application of a 27 kV separation potential with absorbance detection at 485 nm. The use of a 50 microm inner diameter(ID) extended light path capillary (150 microm pathlength) was found to be adequate for determining elevated levels of creatinine in human blood sera, but could not be used to quantify normal levels. Quantification of both normal and elevated levels of creatinine in sera was possible with a 75 microm ID high-sensitivity cell (1200 microm pathlength). Calibration plots using the latter for creatinine in human blood sera spanned the expected clinical range and were linear between 40 microM and 1.2 mM (r2 = 0.996) with an estimated limit of detection of 17 microM (signal-to-noise ratio S/N = 3). A quantitative comparison of results obtained with the reported EMMA method and accepted clinical methodology correlated very well (slope = 1.001).     

Ion flotation of rhodium(III) and palladium(II) with anionic surfactants

The ion flotation of rhodium(III) and palladium(II) with some anionic surfactants has been investigated. Two flotation procedures are proposed for the separation of some platinum metals, based on differences in the kinetic properties of the chloro-complexes of rhodium(III), palladium(II) and platinum(IV). The first involves the selective flotation of Rh(H(2)O)(3+)(6) from PdCl(2-)(4) and PtCl(2-)(6) in dilute hydrochloric acid with sodium dodecylbenzenesulfonate (SDBS). After precipitation of the hydroxide and redissolution in dilute acid, the Rh(III) is converted into Rh(H(2)O)(3+)(6), Pd(II) and Pt(IV) remaining as PdCl(2-)(4) and PtCl(2-)(6) respectively, and separation is achieved by floating the Rh(H(2)O)(3+)(6) with SDBS. The second is for separation of Pd(II). Prior to flotation, the solution of PdCl(2-)(4) and PtCl(2-)(6) is heated with ammonium acetate to convert PdCl(2-)(4) into Pd(NH(3))(2+)(4). The chloro-complex of Pt(IV) is unaffected. The complex cation, Pd(NH(3))(2+)(4), is then selectively floated with SDBS. The procedures are fast, simple and do not require expensive reagents and apparatus.     

Lanczos cluster expansion for non-extensive systems

A cluster expansion of the Lanczos recursion for non-extensive systems is developed based on the plaquette expansion for extensive systems, in which an auxiliary scaling parameter, Ω, plays the role of volume and introduces extensivity into the problem. Connected Hamiltonian moments of the non-extensive system are computed and introduced into the plaquette expansion in the usual way with Ω. The extensive energy is calculated for increasing orders of the expansion in 1/Ω and the ground state and mass gap of the finite few body problem recovered in the limit Ω → ∞. This new non-perturbative method is applied to the case of N bosons interacting harmonically in one dimension and the ground state energy and mass gap in the vacuum sector are calculated exactly.