A Quality Assurance Study for the Analysis of Hydrocarbons in Sediments

Abstract

Two exercises (MEDCAL I and II) were conducted in our Department during November 1984 and October 1986, with participants from the Mediterranean region, for testing the IOC Manual for the determination of petroleum hydrocarbons in sediments (IOC, Manuals and Guides, No. 11).

The gas chromatographic analysis of the saturated hydrocarbon fraction provided, at the best, a precision of 60% (relative standard deviation RSD) for n-alkanes (mean conc. 0.89 μg/g) and 56 % for the unresolved complex mixture (UCM) (mean conc. 16μg/g). The CPI and the pristane/phytane ratio provided better results (13% RSD). The aromatic fractions, analysed by UV-fluorescence, yielded in total a mean concentration of 10μg/g of chrysene equivalents with a 49% RSD.

The extraction-partition step was confirmed to be the main source of error in the analysis because when the results were corrected for recoveries, the RSD were reduced to 17, 30 and 6% for n-alkanes, UCM and total aromatics, respectively. Our reference intra-laboratory precision was, respectively, 18, 14 and 14%.     

Asymmetric Induction via an Intramolecular Haloetherification Reaction of Chiral Ene Acetals: A Novel Approach to Optically Active 1,4- and 1,5-Diols

An asymmetric synthesis of chiral 1,4- and 1,5-diols has been developed from the ene acetals 1a and 1c, prepared from the corresponding aldehydes and chiral C(2)-symmetric diols, involving remote asymmetric induction as a key step. In the first step, treatment of 1 with I(coll)(2)ClO(4) in the presence of an alcohol afforded the macrocyclic acetals (3-5 and 7) in a highly stereoselective manner. Subsequent nucleophilic substitution of iodide followed by a Grignard reaction with complete retention of stereochemistry and a final deprotection of the diphenylethylene or diphenylpropylene unit successfully gave optically active 1,4- and 1,5-diols in good yields.     

Chemical Synthesis of a Circular Protein Domain: Evidence for Folding-Assisted Cyclization

Extremely fast cyclization of the linear polypeptide precursor 1 takes place to form 2 . The reaction appears to be assisted by the native fold of 1 , which positions the reactive ends in close proximity. The circular topology has no influence on the folding or function of 2 .     

Fragmentation of Optically Active (1-Phenylethyl)- and (1-Naphthylethyl)ureas in Refluxing Alcohols: Easy Preparation of Optically Active Amines of High Optical Purity

(1-Phenylethyl)- and (1-naphthylethyl)ureas, obtained in the reaction of racemic amines with optically pure isocyanates, are separated and then decomposed in refluxing alcohols, to afford optically pure secondary amines and optically pure alkyl carbamates in quantitative yields. The scope of this fragmentation for the resolution of racemic mixtures of amines is illustrated by several examples of biologically important compounds. Carbamates obtained by this fragmentation can readily be recycled.     

Synthesis and Polymerization of Optically Active N‐Propargylphosphonamidates: A Novel Helical Polymer Carrying a P‐Chiral Center

Summary: A diastereomeric pair of novel N‐propargylphosphonamidates, HCCCH₂NHP(O)(CH₃)O‐L ‐menthyl was synthesized by the successive condensations of methylphosphonic dichloride with L ‐menthol and propargylamine. The (R)‐P‐isomer ( 1a ) was isolated, and the absolute configuration was determined by XRD. Polymerization of 1a , and a mixture of 1a and (S)‐P‐isomer ( 1b ) was carried out with a zwitterionic Rh complex as a catalyst. cis‐Stereoregular polymers with number‐average molecular weights of 5 600–9 800 were obtained in good yields. Poly( 1a ) and poly( 1a ₂₉‐co‐ 1b ₇₁) exhibited large specific rotations (+408 and −146°), and intense Cotton effects ([θ] = +2.25 and −0.9 × 10⁴ deg · cm² · dmol⁻¹) based on the conjugated polyacetylene backbone around 325 nm in CHCl₃, indicating that these polymers have helical structures, whose predominant helical senses are opposite.

Polymerization of N‐propargylphosphonamidate.     

Dendroclefts: Optically Active Dendritic Receptors for the Selective Recognition and Chiroptical Sensing of Monosaccharide Guests

The enantiomerically pure dendritic receptors with cleft-type recognition sites (dendroclefts) of generation zero ((−)- G0 ), one ((−)- G1 ), and two ((−)- G2 ) (Fig. 1) were prepared for the complexation of monosaccharides via H-bonding. They incorporate a rigid, optically active 9,9′-spirobi[9H-fluorene] core bearing 2,6-bis(carbonylamino)pyridine moieties as H-bonding sites in the 2,2′-positions. The dendritic shells in (−)- G1 and (−)- G2 are made out of a novel type of dendritic wedges of the first ( 8 ; Scheme 2) and second ( 13 ; Scheme 3) generations, which contain only donor O-atoms and are attached to the H-bonding edges of the core via glycine spacers (Scheme 4). The formation of stable 1 : 1 complexes (association constants K_a between 100 and 600 M ⁻¹, T=298 K; Table 2) between the three receptors and pyranosides in CHCl₃ was confirmed by ¹H-NMR and CD binding titrations as well as by Job plot analyses. The degree of dendritic branching was found to exert a profound effect on the stereoselectivity of the recognition processes. The binding enantioselectivity decreases with increasing degree of branching, whereas the diastereoselectivity increases. The ¹H-NMR analysis showed that the N−H⋅⋅⋅O H-bonds between the amide NH groups around the core and the sugar O-atoms become weakened with increasing dendritic generation, presumably due to steric factors and competition from intramolecular H-bonding between these amide groups and the O-atoms of the dendritic shell. The chiroptical properties of the dendroclefts respond to guest binding in a stereoselective manner. Whereas large differential changes are seen in the circular dichroism (CD) spectra of (−)- G0 and (−)- G1 upon complexation of the enantiomeric monosaccharides (Figs. 3 and 4), the CD spectra of the higher-generation derivative (−)- G2 respond to a lesser extent to guest complexation (Fig. 5). This is indicative of a different binding geometry, more remote from the core chromophore. With their higher masses, the dendroclefts (−)- G1 and (−)- G2 are readily recycled from host-guest solutions by gel-permeation chromatography. The strong CD sensory response and the easy recyclability suggest applications of chiral dendroclefts as sensors for biologically important molecules.     

High Syn Selectivity of a SE′ Reaction: Acylation of an Optically Active 1,1-Disilyl-2-alkene. Preliminary communication

The disilane/disilylmethane rearrangement of an optically active disilanyl sulfide 9B was used to prepare an optically active disilylalkene 10 whose absolute configuration was established by X-ray analysis of the bromo derivative 13 (P2₁, a = 7.847 (3) Å, b = 9.487 (3) Å, c = 20.010 (8) Å, β = 82.28° (3), Z = 2). Acylation of 10 furnished an optically active ketone 14 , which was degraded to 16 , a compound of known absolute configuration. The enantiomeric excess of 10 was determined by alkylation with an optically active lithium compound and that of 14 by an optically active NMR.-shift reagent. The S_E′ reaction 10 → 14 was thus shown to proceed with 94% (97% syn/3% anti) stereoselectivity.     

The Application of Active Biomonitoring with the Use of Mosses to Identify Polycyclic Aromatic Hydrocarbons in an Atmospheric Aerosol

The use of biological indicators of environmental quality is an alternative method of monitoring ecosystem pollution. Various groups of contaminants, including organic ones, can be measured in environmental samples. Polycyclic aromatic hydrocarbons (PAHs) have not yet been determined by the moss bag technique. This technique uses several moss species simultaneously in urban areas to select the best biomonitoring of these compounds, which are dangerous to humans and the environment. In this research, a gas chromatography coupled with mass spectrometry was used for the determination of selected PAHs in three species of mosses: Pleurozium schreberi, Sphagnum fallax and Dicranum polysetum (active biomonitoring) and for comparison using an air filter reference method for atmospheric aerosol monitoring. The chlorophyll fluorescence of photosystem II (PSII) was also measured to assess changes in moss viability during the study. As a result of the study, the selective accumulation of selected PAHs by mosses was found, with Pleurozium schreberi being the best bioindicator—9 out of 13 PAHs compounds were determined in this species. The photosynthetic yield of photosystem (II) decreased by 81% during the exposure time. The relationship between PAHs concentrations in mosses and the total suspended particles (TSP) on the filter indicated the possibility of using this bioindicator to trace PAHs in urban areas and to apply the moss bag technique as a method supporting classical instrumental air monitoring.     

L-(-)-Menthol in the Synthesis of Key Synthons for Optically Active Methyl-Branched Insect Pheromones

A synthesis of optically active 4S-methylhexanal, 1-bromo-3S-methylheptane, and 1-bromo-3S-methylundecane, which are key synthons for several methyl-branched insect pheromones, that is based on chemically selective transformations of 6-tosyloxy- and 6-iodoisopropyl-4R-methylhexanoates that are available from L-(-)-menthol was proposed. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 592–593, November–December, 2005.     

Optically Active Cyclophane Receptors for Mono‐ and Disaccharides: The Role of Bidentate Ionic Hydrogen Bonding in Carbohydrate Recognition

A new family of optically active cyclophane receptors for the complexation of mono‐ and disaccharides in competitive protic solvent mixtures is described. Macrocycles (−)‐(R,R,R,R)‐ 1 – 4 feature preorganized binding cavities formed by four 1,1′‐binaphthalene‐2,2′‐diyl phosphate moieties bridged in the 3,3′‐positions by acetylenic or phenylacetylenic spacers. The four phosphodiester groups converge towards the binding cavity and provide efficient bidentate ionic H‐bond acceptor sites (Fig. 2). Benzyloxy groups in the 7,7′‐positions of the 1,1′‐binaphthalene moieties ensure solubility of the nanometer‐sized receptors and prevent undesirable aggregation. The construction of the macrocyclic framework of the four cyclophanes takes advantage of Pd⁰‐catalyzed aryl—acetylene cross‐coupling by the Sonogashira protocol, and oxidative acetylenic homo‐coupling methodology (Schemes 2 and 8 – 10). Several cleft‐type receptors featuring one 1,1′‐binaphthalene‐2,2′‐diyl phosphate moiety were also prepared (Schemes 1, 6, and 7). An undesired side reaction encountered during the synthesis of the target compounds was the formation of naptho[b]furan rings from 3‐ethynylnaphthalene‐2‐ol derivatives, proceeding via 5‐endo‐dig cyclization (Schemes 3 – 5). Computer‐assisted molecular modeling indicated that the macrocycles prefer nonplanar puckered, cyclobutane‐type conformations (Figs. 7 and 8). According to these calculations, receptor (−)‐(R,R,R,R)‐ 1 has, on average, a square binding site, which is complementary in size to one monosaccharide. The three other cyclophanes (−)‐(R,R,R,R)‐ 2 – 4 feature, on average, wider rectangular cavities, providing a good fit to one disaccharide, while being too large for the complexation of one monosaccharide. This substrate selectivity was fully confirmed in ¹H‐NMR binding titrations. The chiroptical properties of the cyclophanes and their nonmacrocyclic precursors were investigated by circular dichroism (CD) spectroscopy. The CD spectra of the acyclic precursors showed a large dependence from the number of 1,1′‐binaphthalene moieties (Fig. 9), and those of the cyclophanes were remarkably influenced by the nature of the functional groups lining the macrocyclic cavity (Fig. 11). Profound differences were also observed between the CD spectra of linear and macrocyclic tetrakis(1,1′‐binaphthalene) scaffolds, which feature very different molecular shapes (Fig. 10). In ¹H‐NMR binding titrations with mono‐ and disaccharides (Fig. 13), concentration ranges were chosen to favor 1 : 1 host−guest binding. This stoichiometry was experimentally established by the curve‐fitting analysis of the titration data and by Job plots. The titration data demonstrate conclusively that the strength of carbohydrate recognition is enhanced with an increasing number of bidentate ionic host−guest H‐bonds (Table 1) in the complex formed. As a result of the formation of these highly stable H‐bonds, carbohydrate complexation in competitive protic solvent mixtures becomes more favorable. Thus, cleft‐type receptors (−)‐(R)‐ 7 and (−)‐(R)‐ 38 with one phosphodiester moiety form weak 1 : 1 complexes only in CD₃CN. In contrast, macrocycle (−)‐(R,R,R,R)‐ 1 with four phosphodiester groups undergoes stable inclusion complexation with monosaccharides in CD₃CN containing 2% CD₃OD. With their larger number of H‐bonding sites, disaccharide substrates bind even more strongly to the four phosphodiester groups lining the cavity of (−)‐(R,R,R,R)‐ 2 and complexation becomes efficient in CD₃CN containing 12% CD₃OD. Finally, the introduction of two additional methyl ester residues further enhances the receptor capacity of (−)‐(R,R,R,R)‐ 3 , and efficient disaccharide complexation occurs already in CD₃CN containing 20% CD₃OD.     

Determination of Polycyclic Aromatic Hydrocarbons in Mangrove Sediments: Comparison of Two Internal Standard Surrogate Methods and Quality-Control Procedures

Two internal standard surrogate (ISS) methods, ISS-I (with m-terphenyl as a single ISS) and ISS-2 (using five deuterated PAHs as a multi-ISS), for the determination of polycyclic aromatic hydrocarbons (PAHs) in mangrove sediments were compared. The recovery percentages of 16 PAHs except naphthalene in HS-6 (a certified reference material) were high, ranging from 69.3 to 111.8% for ISS-1 and from 71.8 to 120.3% for the ISS-2 method. Similarly, the PAH recovery percentages in spiked mangrove sediments and clean sand were lower for ISS-I than for ISS-2, but both methods met the accurate acceptance criteria for PAH recoveries. The reproducibility (i.e. the method precision) between the two ISS methods was also comparable and satisfactory, with relative standard deviation values in most cases within 20% of the data variability. These results indicate that both ISS methods were acceptable for the determination of PAHs in mangrove sediments, despite the fact that the matrix of mangrove sediments may interfere with the PAH recovery efficiency.     

Plutonium Activity Ratios in Plankton: New Evidence of Hold-Up Time in Irish Sea Sediments

The determination of activity ratios for radioisotopes of different half-lives can be used to estimate transit times from a point source to locations further away. For conservative elements, this time is approximately equivalent to the net hydrological transport. However, for non-conservative elements such as plutonium, the additional influence of biogeochemical processes decreases the net transport time. In this study, ²⁴¹Pu and ^239,240Pu concentrations in Irish Sea plankton samples, collected in May 1994, were determined and the ²⁴¹Pu/^239,240Pu ratios calculated. Plutonium-239,240 was measured using a standard method by ion exchange chromatography and alpha counting, and ²⁴¹Pu was determined by liquid scintillation counting using the disk-supported technique. The latter showed some methodological problems, which are briefly discussed. The ²⁴¹Pu/^239,240Pu ratios gave an estimate of the "transit time" from Sellafield to the different sampling points. In fact, this time represents the age of plutonium in plankton, i.e., the time lag between release from Sellafield and detection at the different sampling stations. The mean plutonium age was 17±2 years (n = 10) and 18.6±0.8 years (n = 13) in phytoplankton and zooplankton, respectively. The spatial distribution was reasonably homogeneous over the Irish Sea. The assimilation-elimination processes of plutonium in plankton are rather rapid. Therefore, it may be assumed that, in this time scale, the plutonium concentrations were in equilibrium with surrounding waters. Thus, it is concluded that plutonium was rather old because resuspension-sedimentation processes had occurred that delayed its transport within the Irish Sea. Therefore, the age of plutonium in plankton represented the hold-up time of plutonium in the sediments from the Irish Sea.     

Optically Active Helical Lanthanide Complexes: Storable Chiral Lewis Acidic Catalysts for Enantioselective Diels–Alder Reaction of Siloxydienes

Lanthanide triflates and a series of hexadentate chiral ligand complexes were synthesized. X‐ray‐quality crystals were obtained from mixtures of the lanthanide complexes, which were helical in shape. The complexes showed Lewis acidity and catalyzed the enantioselective Diels–Alder reaction of electron‐rich siloxydienes. The complexes were stable enough to be stored at ambient temperature on a laboratory bench and retained their Lewis acidity even after a month.     

Diaminobenzene as a Novel Reagent for Nitrite Assay in Environmental Samples: Evidence for Its Mechanistic Aspects

Abstract

o-Phenylenediamine has been used as a reagent to quantify nitrites/nitrates in a variety of sample matrices. The method is based on the cyclization reaction between o-phenylenediamine and nitrite in acid medium. The amine undergoes diazotization with nitrite in the presence of acid to form the diazonium ion, which subsequently cyclizes to yield yellowish orange benzotriazole at room temperature with an absorption maximum at 450 nm. The formed dye has been separated, purified, and characterized by IR, NMR, and spectroscopy techniques. The parameters of the reaction between amine and nitrite have been optimized. The effect of interfering ions on the determination of nitrites/nitrates has been described. The developed method has been applied for the determination of residual NO₂ gas present in the ambient air after fixing it as a nitrite ion using sodium arsenite as a trapping medium. The dye formed has been extracted into organic solvent to improve the detection limit during the measurement of low levels of ambient NO₂ in air. The method obeyed Beer's law in the concentration range 0–250 µg in aqueous medium and 0–50 µg in organic medium with molar absorptivity of 4.09 × 10⁴ L mol^?1 cm^?1 and 4.3 × 10⁴ L mol^?1 cm^?1 respectively. Nitrate is determined by reducing it to nitrite after passing through the copperized cadmium reductor column. The developed method has been applied to determine nitrite/nitrate levels in water, soil, and biological samples.