Riccardo Aigotti

Aroma compounds of an Italian wine (Ruché) by HS–SPME analysis coupled with GC–ITMS

Abstract Headspace solid phase micro extraction (HS–SPME) was used for extraction of aroma compounds characterizing a Piedmont wine ( Ruche ) derived from a non aromatic vine. Extracted compounds were identified by ion trap mass spectrometry (ITMS) after gas-chromatographic analysis. In this way a selection of 59 identified primary aromatic compounds, related to the typical flavour of Ruche was made possible. The SPME technique showed peculiar behaviour in that 23 of the 59 compounds identified were not detected by liquid-liquid solvent extraction of the same samples. Subsequent comparison with the aromatic profiles of different wine samples obtained by microvinification from different grape varieties showed similarities between Ruche and the wines, Brachetto and Malvasia , originating from aromatic vines. SPME analysis proved to be useful in understanding aroma compositions of all samples examined, establishing bases for further investigations on the chemical and biochemical mechanisms underlying wine aroma development.

Electrochemical oxidation of organic pollutants at low electrolyte concentrations

The electrochemical oxidation of organic pollutants is a promising process for substances which are recalcitrant to biological degradation. The anodic oxidation of coumaric acid, which is a biorefractory organic pollutant of olive oil manufacturing waste waters, was evaluated on a Pt–Ti electrode. The operating test conditions were compatible with direct discharge of the after-treatment effluent in natural water basins or rivers as regards the electrolyte salt content (Na2SO4=0.02 N). The effect of the applied current density, pH, temperature, initial coumaric acid concentration and of the type of DC feeder (a galvanostat or a simple current rectifier) over the oxidation rate was assessed through a series of batch runs performed in a pilot plant apparatus. Beyond direct oxidation at the Pt-electrode surface, bulk oxidation with hydrogen peroxide, generated through a persulfate-formation/hydrolysis route, was found to be a crucial step in coumaric acid degradation to more biodegradable non-aromatic products. Small quantities of Fe ions were helpful in accelerating the oxidation process. An analysis of the rather complex reaction schemes governing the process is proposed.

Identification and determination of red dyes in confectionery by ion-interaction high-performance liquid chromatography

Abstract In this paper an ion-interaction HPLC method for the separation and determination of red dyes used to decorate home-made sweets is presented. In particular E122, E123 and E124 dyes are considered, with special interest for E123 (amaranth), prohibited by the US Food and Drug Administration in 1976 and by Italian legislation in 1977 and then again permitted (with restrictions) in the European Community in 1994, (94/36 EEC Directive). A RP-ODS stationary phase is used and an ion-interaction reagent (octylammonium phosphate) is added to the hydro-organic eluent [water-acetonitrile (30:70, v/v), pH = 6.4]. Spectrophotometric detection at 520 nm was employed and detection levels below 12 μg/l for the three dyes were achieved. The method is applied to two commercial products, respectively produced in France and in Italy, and the results are discussed in the light of the recent EEC Directive concerning food dyes.

Analysis of regioisomers of polyunsaturated triacylglycerols in marine matrices by HPLC/HRMS.

Natural sources of triacylglycerols containing ω-3 fatty acids are of particular interest due to their protective role against several human diseases. However, as it has been well ascertained, the position of the ω-3 fatty acid on the triacylglycerol backbone influences how digestion occurs. In particular, occurrence at the sn-2 position allows optimal intestinal absorption conditions. The analytical protocol for regioisomer characterisation of fatty acids in a triacylglycerol usually requires the use of stereospecific lipases before instrumental identification. In this paper, we propose a more direct instrumental determination of triacylglycerol composition along with sn-2 positional identification of the fatty acids constituents by Liquid Chromatography-High Resolution Mass Spectrometry. Different intensities of product signals obtained in MS(2) and MS(3) experiments were used to define an interpretative scheme able to rationalise the stereochemistry of the TAGs. Marine matrices like tuna and algae oils have been studied in detail, their triacylglycerols identified and sn-2 positional arrangement of fatty acid constituents assessed.

Photocatalytic degradation of selected anticancer drugs and identification of their transformation products in water by liquid chromatography-high resolution mass spectrometry.

A study on the fate of two antineoplastic drugs, methotrexate and doxorubicin, in the aquatic environment is presented. The investigation involved a study of their decomposition under dark experiments, homogeneous photolysis and heterogeneous photocatalysis using titanium dioxide, the identification of intermediate compounds, as well as the assessment of acute toxicity over time. The analysis were carried out using LC (ESI positive mode) coupled with LTQ-Orbitrap analyser; accurate mass-to-charge ratios of parent ions were reported with inaccuracy below 10mmu, which guarantee the correct assignment of their molecular formula in all cases, while their MS(2) and MS(3) spectra showed several structural-diagnostic ions that allowed to characterize the different transformation products and to discriminate the isobaric species. Fourteen and eight main species were identified subsequently to doxorubicin or methotrexate transformation. The major transformation processes for doxorubicin involved (poli)hydroxylation and/or oxidation of the molecule, or the detachment of the sugar moiety. Methotrexate transformation involved decarboxylation or the molecule cleavage. Acute toxicity measurements showed that not only the two drugs exhibit high toxicity, but also their initial transformation products are highly toxic.

Analysis of chiral carboxylic acids in wine by high-performance liquid chromatography with coupled UV and circular dichroism detection

Abstract A circular dichroism (CD) spectrophotometer, equipped with a flow cell, and a UV detector were connected in series and were used for coupled UV-CD detection of optically active carboxylic acids. The limits of detection and the linear range for the enantiomers of tartaric, malic, lactic and ascorbic acids are reported. Several wines were analysed and CD detection proved to be sensitive enough for accurate determinations. The combined UV-CD detection was helpful for identifying the peaks and allowed the calculation of enantiomeric ratios.

Ion trap tandem mass spectrometric identification of thiabendazole phototransformation products on titanium dioxide

The purpose of this study is to artificially produce degradation intermediates of thiabendazole, which could be reasonably similar to those really present in the environment. The formation of by-products from thiabendazole transformation has been evaluated by adopting irradiated titanium dioxide as a photocatalyst. Several species more hydrophilic than the thiabendazole have been identified and characterized by HPLC-multiple MS. A pattern of reactions accounting for the observed intermediates is proposed. Two different parallel pathways are operating (and through these pathways the transformation of the molecule proceeds) leading to several intermediate compounds. The main steps involved are: (1) the hydroxylation of the molecule on the aromatic ring with the formation of a species having [M+H]+ 218; a further oxidation leads to the ring-opening and to the formation of aldehydic and alcoholic structures ([M+H]+ 270, 268 and 152); and (2) the cleavage of a C-C bond and the formation of a species having [M+H]+ 119.

LC-high-resolution multiple stage spectrometric analysis of diuretic compounds Unusual mass fragmentation pathways

The analysis of diuretic compounds has become of great concern because of their extensive use both in therapy and in illicit treatments (such as masking agents in sport doping and drug abuse). The variety of chemical structures of this class of drugs encouraged the development of new methods and techniques of analysis, especially as regards to acidic compounds. LC/MS has so grown to be the reference technique for this kind of analysis in forensic and anti-doping confirmation purposes. Multiple stage MS permits identification of single drugs with high selectivity, but some unexpected pathways could weaken the entire process. In this work we aim to explain some unusual fragmentation steps using high-resolution MSn. For example, in the case of amiloride an intense product ion in MS3 analysis generates an apparent loss of 10Da. Water adduct formation and successive carbon monoxide elimination can explain this uncommon behavior, which was studied using different ion traps. Bendroflumethiazide MSn spectra show instead three successive HF losses, in spite of the presence of a radical site in the parent structure. Homolytic cleavages with radical ion production occur also in the case of protonated positive ion of ethacrynic acid (loss of chlorine radical) showing that such fragmentation behavior is not so rare as generally reported. Different ionization modes were studied and a tentative correlation with acidic-base properties was done. Multiple stage high-resolution mass spectra of positive and negative ions were discussed.

Complex formation between copper(II) and hippuryl-L-histidyl-L-leucine in aqueous solution: A model for coordination properties of internal chains of proteins

Abstract Complex formation between copper(II) and the peptide hippuryl-L-histidyl-L-leucine (H 2 L + ) was studied in aqueous solution at t = 25°C and I = 0.1 mol·dm −3 by means of potentiometric, visible spectrophotometric, and circular dichroism measurements. In the acidic pH range, potentiometric and spectrophotometric data are consistent with the formation of the monodentate CuL + species. At a half neutralization of proton bound to N(3)-imidazole nitrogen, before forming more stable deprotonated species, precipitation occurs; redissolution of precipitate is obtained when further base is added. Potentiometric data are satisfactorily explained by assuming the formation of the species CuLH° −1 , CuLH − −2 , and CuLH 2− −3 . As regards CuLH − −2 complex, the whole of the data are strongly consistent with three nitrogen donor groups in the equatorial plane. The comparison between CD spectra calculated for CuLH − −2 and CuLH 2− −3 species suggests the participation of the L-leucyl residue to coordination only in the latter complex. Since the N-terminal amino group is not available for coordination, this tripeptide might be a reliable model for coordination properties of internal chains of proteins.

Potentiometric and spectroscopic study of copper(II) complexes with glycyl-glycyl-l-histidyl-l-alanine in aqueous solution

Abstract The complex formation between copper(II) and the tetrapeptide glycyl-glycyl- l -histidyl- l -alanine ([H 3 L] 2+ ) has been studied in aqueous solution at t = 25°C and I = 0.1 mol dm −3 by potentiometric, visible spectrophotometric and circular dichroism measurements. All the experimental techniques show that the complex [CuLH −2 ] − is predominant over a wide pH range, while the monodentate [CuLH] 2+ is formed in the acidic region and a further deprotonated [CuLH −3 ] 2− species exists at pH higher than 10. The formation constants of the three above complexes are reported and a structure is proposed on the basis of spectroscopic results. The structure of [CuLH −2 ] − species very probably involves four nitrogen donors in the plane, excluding coordination by the l -alanine residue, while it seems likely that [CuLH −3 ] 2− is formed by simple dissociation of the N-1 pyrrole hydrogen.