Determination of tributyltin in marine sediment: Comité Consultatif pour la Quantité de Matière (CCQM) pilot study P-18 international intercomparison

The capabilities of National Metrology Institutes (NMIs—those which are members of the Comité Consultatif pour la Quantité de Matière (CCQM)of the CIPM) and selected outside "expert" laboratories to quantitate (C₄H₉)₃Sn⁺ (TBT) in a prepared marine sediment were assessed. This exercise was sanctioned by the 7th CCQM meeting, April 4–6, 2001, as an activity of the Inorganic Analysis Working Group and was jointly piloted by the Institute for National Measurement Standards of the National Research Council of Canada (NRC) and the Laboratory of the Government Chemist (LGC), UK. A total of 11 laboratories submitted results (7 NMIs, and 4 external labs). Two external laboratories utilized a standard calibration approach based on a natural abundance TBT standard, whereas all NMIs relied upon isotope dilution mass spectrometry for quantitation. For this purpose, a species specific ¹¹⁷Sn-enriched TBT standard was supplied by the LGC. No sample preparation methodology was prescribed by the piloting laboratories and, by consequence, a variety of approaches was adopted by the participants, including mechanical shaking, sonication, accelerated solvent extraction, microwave assisted extraction and heating in combination with Grignard derivatization, ethylation and direct sampling. Detection techniques included ICP–MS (with GC and HPLC sample introduction), GC–MS, GC–AED and GC–FPD. Recovery of TBT from a control standard (NRCC CRM PACS-2 marine sediment) averaged 93.5±2.4% (n=14). Results for the pilot material averaged 0.680±0.015 µmol kg^–1 (n=14; 80.7±1.8 µg kg^–1) with a median value of 0.676 µmol kg^–1. Overall, performance was substantially better than state-of-the-art expectations and the satisfactory agreement amongst participants permitted scheduling of a follow-up Key comparison for TBT (K-28), a Pilot intercomparison for DBT (P-43), and certification of the test sediment for TBT content and its release as a new Certified Reference Material (HIPA-1) with a TBT content of 0.679±0.089 µmol kg^–1 (expanded uncertainty, k=2, as Sn) (80.5±10.6 µg kg^–1).Electronic Supplementary Material Supplementary material is available in the online version of this article at .     

International comparison of the determination of cadmium and lead in herb: the Comité Consultatif pour la Quantité de Matière (CCQM) pilot study CCQM-P97

A Comité Consultatif pour la Quantité de Matière (CCQM) inter-laboratory comparison program, CCQM-P97, for the analysis of cadmium and lead in Herba Demodii Styracifolii was organized by the Hong Kong Government Laboratory. The objective of the program was to establish comparability of trace metals analysis in herbal matrices amongst the participating national metrology institutes. The arithmetic mean values of the 13 participants were 0.3186 mg kg⁻¹ (RSD = 11.3%) and 1.650 mg kg⁻¹ (RSD = 11.0%) for cadmium and lead, respectively. The participants using double-isotope dilution mass spectrometry technique for their quantification were found to provide similar mean values to those of non-isotope dilution mass spectrometry users. The observation indicated that trace metal analysis in herbal matrices was not method-dependent, but the use of the highest metrological IDMS approach gave a better precision than other routine calibration methods.     

International comparability of determination of mass fractions of chromium, copper, iron, manganese and zinc in aluminium alloy: Comité Consultatif pour la Quantité de Matière key comparison K42

The degree of equivalence within the participating national metrology institutes for the measurement results of the mass fractions of the analytes Cr, Cu, Fe, Mn and Zn in an aluminium alloy was assessed. This interlaboratory comité consultatif pour la quantité de matière key comparison (CCQM-K42) was organised as an activity of the Inorganic Analytical Working Group of CCQM. In total seven laboratories participated, six of them for all analytes. Measurands were the mass fractions of the analytes in a range of 0.05 and 0.2%. As an outcome the consistency of the results for all elements investigated was acceptable, hence satisfactory comparability was established. An aluminium based certified reference material—undisclosed to the analysts which one it was—was used as test sample. For the purpose of this study homogeneity was tested at BAM. Each laboratory was free to choose any analytical method they wanted to use for the analysis. Consequently various methods of measurement were employed: instrumental neutron activation analysis, X-ray fluorescence spectrometry (XRF) using fused cast-bead method combined with reconstitution technique, inductively coupled plasma optical emission spectrometry (ICP OES) and inductively coupled plasma mass spectrometry. Metrological traceability of the measurement results to the SI unit had to be demonstrated. Therefore, methods such as spark OES or XRF (without fused cast-bead technique)—both of them being most important methods for the analysis of metals and alloys in industrial laboratories—could not be used in the frame of the key comparison.     

International comparison of the determination of the mass fraction of cadmium, chromium, mercury and lead in polypropylene: the Comité Consultatif pour la Quantité de Matière pilot study CCQM-P106

The CCQM-P106 pilot study was organized by the inorganic working group of the Comité Consultatif pour la Quantité de Matière (CCQM) as a feasibility comparison to study the applicability of different analysis methods to the polypropylene sample and test the abilities of the participants for measuring the Cd, Cr, Hg and Pb in polypropylene. National Institute of Metrology P.R. China (NIM) acted as the coordinating laboratory of this pilot study. There were 21 laboratories that submitted the final results. The median values of the mass fraction of Cd, Cr, Hg and Pb were 36.12 mg kg^?1 (the median absolute deviation about the median (MADe) = 0.46 mg kg^?1), 252.5 mg kg^?1 (MADe = 3.4 mg kg^?1), 387.0 mg kg^?1 (MADe = 10.1 mg kg^?1) and 466.2 mg kg^?1 (MADe = 8.9 mg kg^?1), respectively. Isotope dilution mass spectrometry (IDMS), inductively coupled plasma-mass spectrometry (ICP-MS), inductively coupled plasma-optical emission spectrometry (ICP-OES), atomic absorption spectrometry (AAS), instrumental neutron activation analysis (INAA) and X-ray fluorescence (XRF) measurement methods were used, and microwave digestion was used by the most of the participants. In general, very good agreement of the results was observed. Moreover, compared to the results of other methods, the results of IDMS still showed less spread amongst laboratories and had a smaller uncertainty. In addition, the results of some analytes used by XRF and INAA also got satisfactory agreement with the median value.     

Contamination Pétrolière de la Microcouche de Surface du Golfe de Fos-sur-mer (Mer Méditerranéee)

Abstract

In a general study on the petroleum contamination of the Fos-sur-mer Gulf (Mediterranean Sea), the surface microlayer was sampled. We present here the first results reported up to date in this area, based on a sampling carried out with a rotating PVC drum at 3 stations in May 1985.

Very high hydrocarbons concentrations were sometimes observed in the surface film, which appears more heterogeneous than the underlaying water column (0.5-2m). Water samples were filtered through fiberglass filters (0.5-1 μm). Both dissolved and particulate phases were separately extracted and analysed, providing evidence that suspended particles are the major vector for the accumulation and the transport of petroleum pollutants in these neritic waters.

The petroleum origin of “total hydrocarbons” fractions is confirmed by GC and HPLC which reveal characteristic features for n-alkanes and polynuclear aromatic hydrocarbons. HPLC analysis of polar (non-hydrocarbons) fractions could indicate their formation from petroleum components. Furthermore, the comparison with the underlying waters shows that volatilization and biodegradation are the major processes affecting hydrocarbons distribution in these superficial waters.

Biological data (bacteria, chlorophylls, ATP and energetic charge) were simultaneously measured and indicated an important inhibition of phyto- and bacterio- neuston regarding to the planktonic organisms.     

Examining the impact of ancillary ligand basicity on copper(I)–ethylene binding interactions: a DFT study

A theoretical investigation at the density functional theory level (B3LYP) has been conducted to elucidate the impact of ligand basicity on the binding interactions between ethylene and copper(I) ions in [Cu(η ²-C₂H₄)]⁺ and a series of [Cu(L)(η ²-C₂H₄)]⁺ complexes, where L = substituted 1,10-phenanthroline ligands. Molecular orbital analysis shows that binding in [Cu(η ²-C₂H₄)]⁺ primarily involves interaction between the filled ethylene π-bonding orbital and the empty Cu(4s) and Cu(4p) orbitals, with less interaction observed between the low energy Cu(3d) orbitals and the empty ethylene π*-orbital. The presence of electron-donating ligands in the [Cu(L)(η ²-C₂H₄)]⁺ complexes destabilizes the predominantly Cu(3d)-character filled frontier orbital of the [Cu(L)]⁺ fragment, promoting better overlap with the vacant ethylene π*-orbital and increasing Cu → ethylene π-backbonding. Moreover, the energy of the filled [Cu(L)]⁺ frontier orbital and mixing with the ethylene π*-orbital increase with increasing pK _a of the 1,10-phenanthroline ligand. Natural bond orbital analysis reveals an increase in Cu → ethylene electron donation with addition of ligands to [Cu(η ²-C₂H₄)]⁺ and an increase in backbonding with increasing ligand pK _a in the [Cu(L)(η ²-C₂H₄)]⁺ complexes. Energy decomposition analysis (ALMO-EDA) calculations show that, while Cu → ethylene charge transfer (CT) increases with more basic ligands, ethylene → Cu CT and non-CT frozen density and polarization effects become less favorable, yielding little change in copper(I)–ethylene binding energy with ligand pK _a. ALMO-EDA calculations on related [Cu(L)(NCCH₃)]⁺ complexes and calculated free energy changes for the displacement of acetonitrile by ethylene reveal a direct correlation between increasing ligand pK _a and the favorability of ethylene binding, consistent with experimental observations.     

Examining the impact of ancillary ligand basicity on copper(I)–ethylene binding interactions: a DFT study

A theoretical investigation at the density functional theory level (B3LYP) has been conducted to elucidate the impact of ligand basicity on the binding interactions between ethylene and copper(I) ions in [Cu(?? ²-C₂H₄)]⁺ and a series of [Cu(L)(?? ²-C₂H₄)]⁺ complexes, where L?=?substituted 1,10-phenanthroline ligands. Molecular orbital analysis shows that binding in [Cu(?? ²-C₂H₄)]⁺ primarily involves interaction between the filled ethylene ??-bonding orbital and the empty Cu(4s) and Cu(4p) orbitals, with less interaction observed between the low energy Cu(3d) orbitals and the empty ethylene ??*-orbital. The presence of electron-donating ligands in the [Cu(L)(?? ²-C₂H₄)]⁺ complexes destabilizes the predominantly Cu(3d)-character filled frontier orbital of the [Cu(L)]⁺ fragment, promoting better overlap with the vacant ethylene ??*-orbital and increasing Cu????ethylene ??-backbonding. Moreover, the energy of the filled [Cu(L)]⁺ frontier orbital and mixing with the ethylene ??*-orbital increase with increasing pK _a of the 1,10-phenanthroline ligand. Natural bond orbital analysis reveals an increase in Cu????ethylene electron donation with addition of ligands to [Cu(?? ²-C₂H₄)]⁺ and an increase in backbonding with increasing ligand pK _a in the [Cu(L)(?? ²-C₂H₄)]⁺ complexes. Energy decomposition analysis (ALMO-EDA) calculations show that, while Cu????ethylene charge transfer (CT) increases with more basic ligands, ethylene????Cu CT and non-CT frozen density and polarization effects become less favorable, yielding little change in copper(I)?Cethylene binding energy with ligand pK _a. ALMO-EDA calculations on related [Cu(L)(NCCH₃)]⁺ complexes and calculated free energy changes for the displacement of acetonitrile by ethylene reveal a direct correlation between increasing ligand pK _a and the favorability of ethylene binding, consistent with experimental observations.     

Influence de l'acidité, en milieu très acide,sur l'intensité de la transition secondaire de molécules de type φCX(1)X(2)X(3) sans sites formellement protonables

The 00 band of the secondary transition (towards 260 nm) of the benzenic chromophore undergoes, for many molecules whose type is φCX₍₁₎X₍₂₎X₍₃₎ (X = CO₂H, NH⁺₃, φ, OCH₃,OH, H), a surprising increase of its intensity when the acidity of the medium is lowered under pH = 0. Some, on the contrary, undergo a slight decrease. We show that these phenomena, appearing in molecules where there is no functional group to be protonated, can be explained on the grounds of an interaction involving the acid species of the medium and the π cloud of the chromophore. We also study the effect of the interaction of these acid species with the substituent.     

The structure of μ-oxo dimer of aluminium(III) porphyrin: a theoretical study

The gas-phase molecular structure of μ-oxo dimer of aluminium(III) porphyrin, (AlP)₂O, has been studied for the first time by density functional theory calculations using the B3LYP and M06 functionals and triple-ζ valence basis sets. The molecule has two conformers with equilibrium structures of D _4d and D _4h symmetries with parallel macrocycles and aluminium-oxygen distances of 1.680–1.684 Å (M06/cc-pVTZ). The aluminium atom lies out of the plane of the four central nitrogen atoms and forms a square-based pyramid with them, with the following parameters (M06/cc-pVTZ): r(Al–N) = 2.030–2.031 Å, r(N···N) = 2.803–2.804 Å (the side of the pyramid base), z(Al)–z(N) = 0.434–0.446 Å (the height of the pyramid).     

Influence of the anions on the structure and magnetic properties of a series of bis(μ-diphenoxo)-bridged linear trinuclear copper(II) complexes: an experimental and theoretical study

The reaction of H(2)L (N,N'-dimethyl-N,N'-bis(2-hydroxy-3-methoxy-5-methylbenzyl)-ethylenediamine) with different copper salts, in methanol and using a H(2)L/Cu = 2 : 3 molar ratio, led to four new bis(μ-diphenoxo)-bridged Cu(3) complexes of general formula [{Cu(S)(μ-L)}(2)Cu(H(2)O)(2n)]X(2) (S = CH(3)OH, n = 1 and X = BF(4)(-) for (1) or ClO(4)(-) for (2); S = Br(3)(-) anion and n = 1 without any X species for (3); S = H(2)O, n = 0 and X = NO(3)(-) for (4)). The use in the same reaction conditions of 4,4'-bipyridine (4,4'-bipy) as connector led to the chain complex [{Cu(μ-4,4'-bipy)(0.5)(μ-L)}(2)Cu(H(2)O)(2n)](ClO(4))(2)·17H(2)O (5). The structure of the centrosymmetric trinuclear unit in (1)-(5) consists of two [Cu(L)] fragments connected through two phenoxo bridging groups to the central copper(II) ion giving rise to a linear arrangement of the copper(II) ions, where the ligand acts in a compartmental form wrapping the metal centre with a N(2)O(2) tetradentate bridging mode. The coordination polyhedron of the symmetrically related external copper atoms exhibits a geometry very close to square-pyramidal, whereas the central copper(II) atom displays either a tetragonally elongated octahedral geometry or a square-planar geometry. Owing to the steric hindrance promoted by the methoxy groups at the phenyl rings, the whole Cu(3) structure is not planar but folded along the line connecting the phenoxo bridging oxygen atoms of the same ligand. Temperature dependence of the magnetic susceptibility of complexes (1)-(5) was measured, showing strong antiferromagnetic interactions between the central and external atoms through the bis(μ-phenoxo) groups. DFT calculations were also performed (a) to support the experimental values of the coupling constant (J(1)) between the nearest-neighbouring copper atoms, (b) to determine the magnitude of the interactions between next-nearest copper(II) atoms (J(2)) and (c) to study magneto-structural correlations for this kind of bis(μ-diphenoxo) trinuclear copper(II) complex.     

Zwitterionic copper(I) π-complexes with monosubstituted alkynes. Synthesis and X-ray diffraction study of a π-complex of copper(I) chloride with 4-ethynyl-4-hydroxy-2,2,6,6-tetramethylpiperidinium chloride

The first mononuclear π-complex of copper(I) chloride with monosubstituted alkyne of the formula [(C₉H₁₆NH₂(OH)C≡CH)CuCl₂] was obtained in the system CuCl-HCl-H₂O-(C₉H₁₆NH₂(OH)C≡CH)Cl (C₉H₁₆NH ₂ ⁺ (OH)C≡CH is the 4-ethynyl-4-hydroxy-2,2,6,6-tetramethylpiperidinium cation) and studied by single-crystal X-ray and X-ray powder diffraction. The crystals are monoclinic: a = 16.868(8) Å, b = 13.177(8) Å, c = 13.32(1) Å, γ = 103.50(4)°, space group P2₁/b, Z = 8. The structure of the complex contains two crystallographically independent zwitterionic entities of the formula [(C₉H₁₆NH₂(OH)C≡CH)CuCl₂], which result from π-coordination of the potential π-bidentate bond C≡C of the organic cation to one Cu(I) atom of the inorganic anion CuCl ₂ ^? . The distances Cu-m (m is the midpoint of the C≡C bond) are 1.91(2) Å. Along with weak intermolecular hydrogen bonds ≡CH...Cl and intramolecular contacts OH...Cl, the structure is stabilized by a directed ionic interaction through strong NH...Cl bonds.     

Binuclear copper(II) complexes of 1-amidino-O-alkylurea (alkyl = n-propyl,n-butyl,or i-butyl) and vanadate: an EPR study

Five new complexes of bis(1-amidino-O-alkylurea)Cu(II)vanadate where alkyl?=?methyl, ethyl, n-propyl, n-butyl or i-butyl have been synthesized by reaction of ammonium metavanadate with bis(1-amidino-O-alkylurea)Cu(II)perchlorate complexes. Electron paramagnetic resonance (EPR) spectra of bis(1-amidino-O-n-propylurea)Cu(II)vanadate (1), bis(1-amidino-O-n-butylurea)Cu(II)vanadate (2) and bis(1-amidino-O-i-butylurea)Cu(II)vanadate (3) gave half-field signal (ΔM _s?=?±2) ca 1623G, in addition to fine structure due to zero field splitting (ZFS) characteristics of the S?=?1 system. From the observed ZFS the average Cu–Cu distance was estimated. The isotropic exchange constant J was evaluated by recording EPR spectra at different temperatures. The photoacoustic signal of the complexes indicated square-planar geometry around Cu²⁺. X-ray powder diffraction studies on 2 suggested orthorhombic structure with unit cell dimensions a?=?21.11?Å, b?=?24.11?Å, c?=?27.11?Å, α?=?β?=?γ?=?90°. The crystal structure of bis(1-amidino-O-n-butylurea)Cu(II)perchlorate is also reported.     

Synthesis, crystal structures and magnetic properties of bis(μ-dialkoxo)-bridged linear trinuclear copper(II) complexes with aminoalcohol ligands: a theoretical/experimental magneto-structural study

The bis(μ-dialkoxo)-bridged trinuclear copper(II) complexes [Cu(3)(ap)(4)(ClO(4))(2)EtOH] (1), [Cu(3)(ap)(4)(NO(3))(2)] (2), [Cu(3)(ap)(4)Br(2)] (3) and [Cu(3)(ae)(4)(NO(3))(2)] (4) (ae = 2-aminoethanolato and ap = 3-aminopropanolato) have been synthesised via self-assembly from chelating aminoalcohol ligands with the corresponding copper(II) salts. The complexes are characterised by single-crystal X-ray diffraction analyses and variable temperature magnetic measurements. The crystal structures of complexes 1-4 consist of slightly bent linear or linear trinuclear [Cu(3)(aa)(4)](2+) (aa = aminoalcoholato) units to which the perchlorate, nitrate or bromide anions are weakly coordinated. The adjacent trinuclear units of 1-4 are connected together by hydrogen bonds and bridging nitrate or bromide anions resulting in the formation of 2D layers. Magnetic studies of 1, 2 and 4 show that J values vary from -379 to +36.0 cm(-1) as the Cu-O-Cu angle (θ) and the out-of-plane shift of the carbon atom of the bridging alkoxo group (τ) vary from 103.7 to 94.4° and from 0.9 to 35.5°, respectively. Magnetic exchange coupling constants calculated by DFT methods are of the same nature and magnitude as the experimental ones. For complexes 1, 2 and 4, which have complementarity effects between the θ and τ angles (small θ values are associated with large τ values and vice versa), an almost linear relationship between the calculated J values with θ angles could be established, thus supporting that the θ and τ angles are the two key structural factors that determine the magnetic exchange coupling for such a type of compounds. Complex 3 does not obey this linear correlation because of the existence of counter-complementarity effects between these angles (small θ values are associated with small τ values and vice versa). It is of interest that the theoretical calculations for the magnetic exchange interaction between next-nearest neighbours indicate that the usual approximation in experimental studies of neglecting the magnetic coupling between the next-nearest neighbours in linear trinuclear complexes could lead to considerable errors, especially when J(1) and J(2) are of the same order of magnitude as J(3).     

Grafted poly(1→4-β-glucan) strands on silica: a comparative study of surface reactivity as a function of grafting density

Grafted poly(β-glucan) (β-glu) strands on the surface of silica are synthesized with varying degrees of grafting density, and display an amorphous-like environment via (13)C CP/MAS NMR spectroscopy. Thermal gravimetric analysis of these materials under oxidative conditions shows increased β-glu thermal stability with higher degrees of grafting density. The range of temperature stability between the most and least hydrogen-bound grafted β-glu strands spans 321 to 260 °C. This range is bound by the combustion temperature previously measured for crystalline and amorphous cellulose, with the former having greater oxidative stability, and is likely controlled by the extent of hydrogen bonding of a grafted β-glu strand with the underlying silica surface. When using these materials as reactants for glycosidic bond hydrolysis, the total number of reducing ends formed during reaction is quantified using a BCA colorimetric assay. Results demonstrate that the material with greatest interaction with silica surface silanols undergoes hydrolysis at an initial rate that is 6-fold higher than the material with the lowest degree of such interaction. The role of the surface as a reactive interface that can endow oxidative stability and promote hydrolysis activity has broad implications for surface-catalyzed processes dealing with biomass-derived polymers.     

Reactivity of nickel(II) and copper(II) complexes of a β-aminohydrazone ligand with pyridine-2-aldehyde: macrocyclization vs unprecedented pyrazole ring synthesis via C-C bond-forming reaction

The synthesis and characterization of a mononuclear nickel(II) complex [Ni(L(2))](ClO(4))(2) (1) and an analogous mononuclear copper(II) complex [Cu(L(2))](ClO(4))(2) (2) of a 15-membered azamacrocycle (L(2) = 3-(2-pyridyl)-6,8,8,13,13,15-hexamethyl-1,2,4,5,9,12-hexaazacyclopentadeca-5,15-diene) are reported. The macrocyclic ligand is formed during the reaction of 4,4,9,9-tetramethyl-5,8-diazadodecane-2,11-dione dihydrazone (L(1)) with pyridine-2-aldehyde (PyCHO) templated by metal ions. The X-ray crystal structure of 1 exhibits a distorted square-pyramidal coordination geometry, where the metal ion sits in the macrocyclic cavity and the pendant pyridine group of L(2) occupies the axial position. While 1 is stable in the presence of an excess of PyCHO, 2 reacts further with copper(II) salt and PyCHO to form a mononuclear copper(I) complex, [Cu(H(2)L(3))](ClO(4))(3) (3). The structure of the complex cation of 3 reveals a distorted tetrahedral coordination geometry at the copper center with a pseudo 2-fold screw axis. A two-dimensional (2D) polymeric copper(II) complex, {[Cu(2)(L(4))(2)](ClO(4))(2)}(n) (4) is obtained by reacting complex 2 (or [Ni(L(1))](ClO(4))(2)) with copper(II) perchlorate and pyridine-2-aldehyde in a methanol-water solvent mixture. Complex 4 is also obtained by treating 3 with copper(II) perchlorate and pyridine-2-aldehyde in the presence of a base. The X-ray structural analysis of 4 confirms the formation of a pyrazolate bridged dimeric copper(II) complex. The extended structure in the solid state of 4 revealed the formation of a 2D coordination polymer with the dimeric core as the repeating unit. The ligand (HL(4)) in 4 is a 3,4,5-trisubstituted pyrazole ring formed in situ via C-C bond formation and represents an unprecedented transformation reaction.