Evaluation of chromatographic and spectroscopic methods for the analysis of petroleum-derived compounds in the environment

Summary Analytical protocols have been adapted for the study of hydrocarbons at the trace level in the environment. Various samples, including sediments and biota, were collected from the Kuwaiti environment, treated according to the protocol and analyzed by chromatographic and spectroscopic methods. The methods used were synchronous scanning fluorescence spectroscopy (SSFS); high-performance liquid chromatography (HPLC) on C18 reversed-phase and NH2 normal-phase columns with UV and fluorescence detectors; gas chromatography on fused-silica capillary columns (GC) with flame ionization detector (FID), mass spectrometer (MS) and flame photometric detector (FPD); and high-resolution molecular spectrofluorimetry in Shpol'skii matrix at 10 K (HRSS). The different methods were found to give complementary information. SSFS was useful for fast evaluation and preliminary assessment of oil pollution during extended programs; it permitted sample selection for deeper analyses but, when applied to biota, needed special care in the clean-up procedure. GC/FID, was used to analyze saturated and ethylenic compounds and was useful for obtaining information on the origin of hydrocarbons but inconvenient for analyzing the aromatic fraction. GC/FPD was difficult to use with sediment samples and yielded little information on biota samples, although it did permit confirmation of high oil contamination in some examples. HPLC on a normal-phase column with UV and fluorescence detectors was useful for the fractionation of samples and for the separation of different families of aromatic compounds according to aromatic carbon number. GC/MS was used to quantify polycyclic aromatic hydrocarbons (PAHs) of less than four cycles but was not sensitive enough for PAHs of higher molecular weight. HRSS, however, was useful for the quantification of heavy PAHs and was also faster, could be automated, and gave accurate results. However, in an oil-pollution study, it must be backed up by the other techniques. In fact, no single analytical technique was found to be sufficient, and only judicious combinations of the tested techniques yielded adequate information on the origin of hydrocarbons in the environment.     

Characterization of carboxylated nanolatexes by capillary electrophoresis

Poly(styrene-co-acrylic acid) (St/AA) and poly(styrene-co-methacrylic acid) (St/MA) nanolatexes with different acid contents were prepared by emulsion copolymerization and were analyzed by capillary electrophoresis (CE) and by laser doppler velocimetry (LDV). Due to the intrinsic differences in the methodologies, CE (separative technique) and LDV (zetametry, nonseparative technique) lead to very different electrophoretic mobility distributions. Beyond these differences, the variation of the electrophoretic mobility is a complex and nonlinear function of the hydrodynamic radius, the ionic strength, and the zeta potential. To gain better insight on the influence of the ionic strength and the acid content on the electrophoretic behavior of the nanolatexes, the electrophoretic mobility data were changed into surface charge densities using the O'Brien, White, and Ohshima modeling. This approach leads to the conclusion that the surface charge density is mainly controlled at high ionic strength (～50 mM) by the adsorption of anionic surfactants coming from the sample. On the contrary, at low ionic strength, and/or in the presence of neutral surfactant in the electrolyte, the acid content was the main parameter controlling the surface charge density of the nanolatexes.     

Biosensors elaborated on gold nanoparticles, a PM-IRRAS characterisation of the IgG binding efficiency

This work is focused on studying the grafting of gold nanoparticles (Np) on a cystamine self-assembled monolayer on gold, in order to build sensitive immunosensors. The synthesis and deposition of gold nanoparticles, 13 and 55 nm sizes, were characterised by combining Polarisation Modulation Infrared Reflection-Absorption Spectroscopy (PM-IRRAS), X-ray Photoelectron Spectroscopy (XPS) Surface Enhanced Raman Scattering (SERS), and Atomic Force Microscopy (AFM) which all indicated the formation of a dispersed layer of nanoparticles. This observation is explained by the compromise between the high reactivity of amine-terminated layers towards gold, and interparticle repulsions. Nps were then functionalised with antibody probes, and the recognition by an anti-rIgG was assayed both on planar and Np gold surfaces.The important result is that nanoparticles of 55 nm are preferable for the following reasons: they enable to build a denser and well dispersed layer and they increase both the number of receptors (IgGs) and their accessibility. Beside these geometric improvements, a net enhancement of the Raman signal was observed on the 55 nm nanoparticle layer, making this new platform promising for optical detection based biosensors.     

Stereoselective organocatalytic one-pot α,α-bifunctionalization of acetaldehyde by a tandem Mannich reaction/electrophilic amination

The first asymmetric organocatalyzed one-pot α,α-bifunctionalization of acetaldehyde with two different electrophiles is described. A diarylprolinol silyl ether-catalyzed reaction of acetaldehyde with an imine and di-tert-butyl azodicarboxylate affords syn-2,3-diaminoalcohols with excellent ee values of up to 98%. This methodology was successfully applied to the synthesis of a chiral α,β-diaminocarboxylic acid.     

Examination of Template Structural Effects on CEC Chiral Separation Performance of Molecule Imprinted Polymers Made by a Generalized Preparation Protocol

Some acidic chiral templates were used to prepare open tubular (OT) molecule imprinted polymer (MIP) capillary columns to explore the effects of molecular structures of templates on chiral recognition capabilities and to verify the feasibility of the general MIP preparation protocol introduced in the previous study. The templates are phenyl carboxylic acids and their derivatives. Optimization was carried out for chiral separation of template enantiomers for each MIP column through varying pH and composition of eluent. It was found that the preparation protocol can be successfully applied for the appropriate templates with functional groups fulfilling the three-points interaction rule. The chiral separation performances were quite satisfactory for MIPs of such templates although they are yet inferior to the separation performances of the MIP columns fabricated with the templates of profen drugs (2-arylpropionic acids with a large substituent on the phenyl ring). Subtle variations of the template molecular structures have been found to be critical to enhance chiral recognition ability of the resultant MIP column.     

An Identification Problem for First-Order Degenerate Differential Equations

We study a first-order identification problem in a Banach space. We discuss the nondegenerate and mainly the degenerate case. As a first step, suitable hypotheses on the involved closed linear operators are made in order to obtain unique solvability after reduction to a nondegenerate case; the general case is then handled with the help of new results on convolutions. Some applications to partial differential equations motivate this abstract approach.Communicated by I. GalliganiWork partially supported by MIUR (Ministero dell’ Istruzione, dell’ Università e dalla Ricerca), Project PRIN 2004011204 “Analisi Matematica nei Problemi Inversi,” and by the University of Bologna Funds for Selected Research Topics.     

Liquid chromatographic retention of homologous alkanes in the two states of C18-bonded reversed phase silicas

Summary LiChrosorb Si100 densely grafted with octadecylmonofunctional reagents and the similar commerical LiChrosorb RP 18 have been studied in RP-HPLC, with water-methanol mobile phases at different temperatures. They exhibit a phase transition revealing two different states of bonded film as we have previously shown on densely grafted C18 or C22 macroporous silicas.The measurement of the capacity factors of the alkane homologous series indicated a discontinuity in the plot (logK, N) at a critical number whose value is dependent on temperature. Two different forms of these curves can be observed above and below the transition, revealing the influence of bonded film state on the retention mechanism.     

Etudes des sélénophènes mono et bisubstitués par Résonance Magnétique de 1H et de 13C

Proton and carbon magnetic resonance spectra of mono-and disubstituted selenophenes are investigated. The proton chemical shifts are discussed in terms of magnetic anisotropy and electric field effects of the substituents, with a view to studying the conformational equilibrium of the carbonyl group. π Electronic charges, computed by the PPP method, are correlated with the proton and carbon chemical shifts. The coupling constants between ¹³C and ¹H (1, 2 or 3 bonds) and ¹³C? ⁷⁷Se are shown to be good structural parameters and a set of substituent additivity constants is calculated.