New metallomolecular wires based on carbon-rich bridging systems: a systematic study

This dissertation presents and discusses the preparation of molecular wires (MW) candidates that would then be probed for electron transfer properties. These wires are bridged by 1,4-diethynylbenzene derivatives with alkoxy side chains with palladium and ruthenium metal complex termini. Characterization of these compounds was performed by usual spectroscopic techniques like 1H, 13C{1H} and 31P{1H} NMR, MS, FTIR and UV-Vis as well as by cyclic voltammetry which allowed classifying the candidates in the Robin–Day system and determination of bridges side chain and length effects on electronic transport. Preparation of the 1,4-diethynylbenzene derivatives was done with synthetic pathways that relied heavily in palladium catalyzed cross-couplings (Sonogashira). A family of single ringed 1,4-diethynylbenzene ligands with different length alkoxy side chains (OCH3, OC2H5, OC7H15) was thus prepared allowing for the influence of these ring decorations to be assessed. The ruthenium binuclear rods showed communication between metal centres only when the shorter ligands were used whereas the longer Ru complexes showed only one redox pair in CV studies which is in agreement to non-communicating metal centres. Cyclic voltammetry studies show irreversible one wave processes for palladium dinuclear complexes, making these rods function as molecular insulators. Fluorescence decay studies performed on the prepared compounds (ligands and complexes) show a pattern of decreasing decay times upon coordination to the metal centres which can due to ligand charge redistribution upon coordination leading to non-radiative relaxation paths. Regarding the X-ray structures, two new ligand related structures were obtained as well as new structure for a palladium rod. The effect of the side chains was observed to be important to the wires’ electronic properties when comparing with the analogues without a side chain. The effect brought by longer chains is nevertheless almost negligible.

Evolution of ethyl carbamate during Madeira wine ageing by GC-MS: a new methodology

Recently, ethyl carbamate (EC) was reclassified by the International Agency for Research on Cancer (IARC) as "probably carcinogenic to humans" and occurs mainly in fermented beverages. Nowadays many countries have set limit values for EC in alcoholic beverages. In this sense and taking into account the low concentrations found in alcoholic beverages, the scientific community has shown interest for the development of new analytical methods, whereby its simplification plays an important role in the EC control and prevention. Firstly, a simple, rapid and sensitive methodology was developed for the EC quantification in fortified wines by microextraction by packed sorbent (MEPS) with gas chromatography coupled with a mass spectrometer detector (GC-MS). This method showed good linearity (R2 = 0.999) and sensitivity (LOD = 1.5 μg/L). The accuracy of the method was assessed by means of repeatability and reproducibility (RSD < 7%). Moreover, a good recovery has been demonstrated (97 – 106%) as well as its applicability (16 fortified wines). Thus, the developed methodology has proven to be an excellent approach for routine quantification of EC in fortified wines. The EC evolution was also evaluated during a year and half of Madeira wine ageing submitted to two traditional ageing methods, estufagem and canteiro, in order to evaluate the formation kinetic. The results revealed that estufagem process increased the formation kinetic and promoted a linear increase of the EC concentration (R2 ≥ 0.977), proportionally to the ageing time (4 months). However, when the wines are firstly submitted to estufagem and then undergo canteiro ageing, the EC values remain almost constant during the following 14 months. The results suggest that estufagem does not seem to be the critical factor in the EC formation, but instead the amount of precursors in the medium.

Investigation of urinary volatile organic metabolites as potential cancer biomarkers by solid-phase microextraction in combination with gas chromatography-mass spectrometry

BACKGROUND: Non-invasive diagnostic strategies aimed at identifying biomarkers of cancer are of great interest for early cancer detection. Urine is potentially a rich source of volatile organic metabolites (VOMs) that can be used as potential cancer biomarkers. Our aim was to develop a generally reliable, rapid, sensitive, and robust analytical method for screening large numbers of urine samples, resulting in a broad spectrum of native VOMs, as a tool to evaluate the potential of these metabolites in the early diagnosis of cancer. METHODS: To investigate urinary volatile metabolites as potential cancer biomarkers, urine samples from 33 cancer patients (oncological group: 14 leukaemia, 12 colorectal and 7 lymphoma) and 21 healthy (control group, cancer-free) individuals were qualitatively and quantitatively analysed. Dynamic solid-phase microextraction in headspace mode (dHS-SPME) using a carboxenpolydimethylsiloxane (CAR/PDMS) sorbent in combination with GC-qMS-based metabolomics was applied to isolate and identify the volatile metabolites. This method provides a potential non-invasive method for early cancer diagnosis as a first approach. To fulfil this objective, three important dHS-SPME experimental parameters that influence extraction efficiency (fibre coating, extraction time and temperature of sampling) were optimised using a univariate optimisation design. The highest extraction efficiency was obtained when sampling was performed at 501C for 60min using samples with high ionic strengths (17% sodium chloride, wv 1) and under agitation. RESULTS: A total of 82 volatile metabolites belonging to distinct chemical classes were identified in the control and oncological groups. Benzene derivatives, terpenoids and phenols were the most common classes for the oncological group, whereas ketones and sulphur compounds were the main classes that were isolated from the urine headspace of healthy subjects. The results demonstrate that compound concentrations were dramatically different between cancer patients and healthy volunteers. The positive rates of 16 patients among the 82 identified were found to be statistically different (Po0.05). A significant increase in the peak area of 2-methyl3-phenyl-2-propenal, p-cymene, anisole, 4-methyl-phenol and 1,2-dihydro-1,1,6-trimethyl-naphthalene in cancer patients was observed. On average, statistically significant lower abundances of dimethyl disulphide were found in cancer patients. CONCLUSIONS: Gas chromatographic peak areas were submitted to multivariate analysis (principal component analysis and supervised linear discriminant analysis) to visualise clusters within cases and to detect the volatile metabolites that are able to differentiate cancer patients from healthy individuals. Very good discrimination within cancer groups and between cancer and control groups was achieved.

Characterization of volatile substances in apples from rosaceae family by headspace solid‐phase microextraction followed by GC‐qMS

The volatile composition of different apple varieties of Malus domestica Borkh. species from different geographic regions at Madeira Islands, namely Ponta do Pargo (PP), Porto Santo (PS), and Santo da Serra (SS) was established by headspace solid-phase microextraction (HS-SPME) procedure followed by GC-MS (GC-qMS) analysis. Significant parameters affecting sorption process such as fiber coating, extraction temperature,extractiontime,sampleamount,dilutionfactor,ionicstrength,anddesorption time,wereoptimizedanddiscussed.TheSPMEfibercoatedwith50/30 lmdivinylbenzene/carboxen/PDMS (DVB/CAR/PDMS) afforded highest extraction efficiency of volatile compounds, providing the best sensitivity for the target volatiles, particularly whenthesampleswereextractedat508Cfor30 minwithconstantmagneticstirring. A qualitative and semi-quantitative analysis between the investigated apple species has been established. It was possible to identify about 100 of volatile compounds amongpulp(46,45,and39),peel(64,60,and64),andentirefruit(65,43,and50)inPP, PS,andSSapples,respectively.Ethylesters,terpenes,andhigheralcoholswerefound tobethemostrepresentativevolatiles. a-Farnesene,hexan-1-olandhexyl2-methylbutyratewerethecompoundsfoundinthevolatileprofileofstudiedappleswiththelargestGCarea,representing,onaverage,24.71,14.06,and10.80%ofthetotalvolatilefractionfromPP,PS,andSSapples.InPPentireapple,themostabundantcompoundsidentified were a-farnesene (30.49%), the unknown compound m/z (69, 101, 157) (21.82%) andhexylacetate(6.57%).RegardingPSentireapplethemajorcompoundswere a-farnesene(16.87%),estragole(15.43%),hexan-1-ol(10.94),andE-2-hexenal(10.67).a-Farnesene(30.3%),hexan-1-ol(18.90%),2-methylbutanoicacid(4.7%),andpentan-1-ol(4.6%) werealsofoundasSSentireapplevolatilespresentinahigherrelativecontent.Principal component analysis (PCA) of the results clustered the apples into three groups according to geographic origin. Linear discriminant analysis (LDA) was performed in order to detect the volatile compounds able to differentiate the three kinds of apples investigated. The most important contributions to the differentiation of the PP, PS, and SS apples were ethyl hexanoate, hexyl 2-methylbutyrate, E,E-2,4-heptadienal, pethylstyrene,andE-2-hexenal.