Dr Monica Felipe-Sotelo


Lecturer in Radiation and Analytical Chemistry
+44 (0)1483 686837
15 AZ 03

Academic and research departments

School of Chemistry and Chemical Engineering.

About

Research interests

  • Creation of reliable spectral databases for the characterisation of radionuclide solid phases:
    • Investigation of radionuclide mineralisation under environmental and repository conditions.
    • Comprehensive characterisation of solid phases by XRD, EXAFS, XANES, TRLFS, FTIR, Raman and ion beam techniques.
  • Study of the dynamics of radionuclides under environmental conditions:
    • Improvement of purification procedures leading to selective and sensitive methods for the determination of radionuclides at ultra-trace levels by ICP-MS .
    • Investigation of procedures for the removal of isobaric interferences on ICP-MS.
  • Development of non-separative speciation schemes by combination of advanced spectroscopic techniques and multivariate statistics

Publications

Ifrah Yusuf, Fabio Flagiello, Neil I Ward, Harvey Arellano-García, Claudio Avignone-Rossa, Mónica Felipe-Sotelo (2020);Valorisation of banana peels by hydrothermal carbonisation: Potential use of the hydrochar and liquid by-product for water purification and energy conversion, In: Bioresource Technology Reports12100582 Elsevier Ltd

Banana peels were used as feedstock to produce a carbon dense hydrochar for the removal of toxic metals from wastewater. Compared to the biomass feedstock (41.3% mass C), the banana peel hydrochar possesses higher carbon (54–72% mass C) and lower ash contents. The carbonised banana peels treated between 150 and 300 °C (1−2h) demonstrated an excellent ability to remove Cd2+ (5–100 mg L−1), achieving 99% removal, in comparison with 75% for the raw peel. The liquid by-product generated in the carbonisation process was tested as feedstock in microbial electrochemical devices, showing significant reduction in the chemical oxygen demand levels (initially 10–25 103 mg L−1), associated with the production of electrical outputs; 81–85% reduction with microbial communities from compost, and 53–85% with anaerobic sludge. The results demonstrate the complete utilization of waste from mass cultivation of banana, providing a full-cycle solution for the pollution associated to this important crop. [Display omitted] •Hydrothermal carbonisation is a sustainable solution for waste in banana industry.•Hydrochars from banana peels are effective sorbents of Cd2+ ion from water.•Promising use of liquid by-product from hydrocharring for bioelectrochemical cells.

M Jaafar, A Shrivastava, S Rai Bose, M Felipe-Sotelo, NEIL IAN WARD, N.I Ward (2021)Transfer of arsenic, manganese and iron from water to soil and rice plants: An evaluation of changes in dietary intake caused by washing and cooking rice with groundwater from the Bengal Delta, India, In: Journal of food composition and analysis96103748 Elsevier Inc

Contamination of groundwater with arsenic from natural sources is endemic in the West Bengal region of India. Despite increased awareness regarding the consumption of safe water for drinking, the use of groundwater for agricultural purposes, cooking and other domestic tasks still prevails. This study investigates the accumulation of As, Mn and Fe in paddy soils irrigated with groundwater and evaluates the levels of these elements in the different parts of the rice plants. The results show that although there is a significant accumulation of As, Mn and Fe in the soils irrigated with groundwater, the uptake by the grains is not proportional to the concentrations in the soils. Arsenic is accumulated mainly in the roots, followed by straw and grains, and significant amounts of arsenic are removed by de-husking of the rice (86–88 % of As in the wholegrain). The evaluation of the effect of washing and cooking the rice with groundwater shows that there is a marked increase in the arsenic levels of cooked rice (up to 232 %). However, the accumulation is highly dependent on the type of rice, with processed commercial samples (parboiled) having a lower capacity to retain arsenic than the rice varieties utilised by the local villagers.

HARRISON FROST, THOMAS BOND, T. Sizmur, MONICA FELIPE-SOTELO (2022)A review of microplastic fibres: generation, transport, and vectors for metal(loid)s in terrestrial environments, In: Environmental science : processes & impacts RSC
Farzad Foroutan, Athanasios Nikolaou, Benjamin A. Kyffin, Ruan M. Elliott, Monica Felipe-Sotelo, Jorge Gutierrez-Merino, Daniela Carta (2020)Multifunctional phosphate-based glass fibres prepared via electrospinning of coacervate precursors: controlled delivery, biocompatibility and antibacterial activity, In: Materialia14 Elsevier B.V

There is an increasing demand for new biomaterials that both rapidly stimulate healing and prevent infections. Being bioresorbable, phosphate-glass fibres can simultaneously induce tissue regeneration and deliver therapeutic agents (e.g. antibacterial ions) in a controlled way. Here we present a series of copper-doped phosphate-based glass fibres in the P2O5-CaO-Na2O-(CuO)x system (x = 0, 1, 3, and 5 mol%) prepared for the first time via electrospinning of coacervate precursors. This method presents several advantages over the conventional high temperature melt spinning; the synthesis of the coacervate occurs at room temperature and in aqueous solution allowing the incorporation of temperature sensitive molecules. Moreover, electrospinning is an inexpensive, sustainable, easily scalable manufacturing process. The fibres produced are cotton-like, fully amorphous with an average diameter in the range 1–3 µm. Dissolution studies on cations (Ca2+, Na+ and Cu2+) and phosphate anions (PO43−, P2O74−, and P3O105−) show a gradual release of all species in solution over time, ideal for controlled drug delivery applications. The antibacterial activity against both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria was found to increase with increasing Cu2+ content and was found to be more effective against E. coli than against S. aureus. Interestingly, Cu2+ content seem to have a positive effect on cytocompatibility. Tests performed on osteoblast-like MG63 osteosarcoma cells have shown that the copper doped phosphate-glass fibres have a significantly better capacity to regenerate bone tissue than the undoped glass fibres. These findings suggest that phosphate-based glass fibres are promising multifunctional biomaterials for both antibacterial activity and tissue regeneration. [Display omitted]

Malgorzata Gbylik-Sikorska, Anna Gajda, Monica Felipe-Sotelo, Manuela Canica, Adriana Cabal-Rosel, Tanel Tenson, Marta Korinkova, Kroot Arbo, Veljo Kisand, Gerhard Rab, Martin Brandtner (2023)Investigation of 29 Antimicrobial Compounds in Soil Using Newly Developed UHPLC-MS/MS Method, In: Molecules28(18)6496 MDPI

While the prudent and reasonable use of veterinary antimicrobial agents in food-producing animals is necessary, researchers over the decades have shown that these antimicrobial agents can spread into the environment through livestock manure and wastewater. The analysis of the occurrence of antimicrobial compounds in soil samples is of a great importance to determine potential impacts on human and animal health and the environment. In this study, an affordable, rugged and simple analytical method has been developed for the determination of twenty-nine antimicrobial compounds from five different classes (tetracyclines, fluoro(quinolones), macrolides, sulfonamides and diaminopirimidines). Liquid-liquid extraction (LLE) with extract filtration combined with ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) was the best strategy for the simultaneous determination of all analytes. The developed method was validated according to the Commission Implementing Regulation (EU) 2021/808. The limit of detections (LODs) ranged from 0.5 to 2.0 mu g/kg, while the limit of quantitation (LOQ) was established at 1.0 to 20.0 mu g/kg. The developed method was successfully applied for the determination of antimicrobial residues in one hundred and eighteen soil samples obtained from four European countries (Austria, Czech Republic, Estonia and Portugal). Doxycycline in the concentration levels of 9.07 mu g/kg-20.6 mu g/kg was detected in eight of the analysed samples. Samples were collected from areas where natural fertilizers (swine or cow manure) were applied. Our method can be efficiently used to monitor anti-microbial compounds in soil samples.

Kathryn Lawson-Wood, Maisarah Jaafar, Mónica Felipe-Sotelo, Neil I. Ward (2021)Investigation of the uptake of molybdenum by plants from Argentinean groundwater, In: Environmental science and pollution research international28(35)pp. 48929-48941 Springer Berlin Heidelberg

Some regions of Argentina are affected by high concentrations of molybdenum, arsenic and vanadium from natural sources in their groundwater. In particular, Mo levels in groundwater from Eduardo Castex (La Pampa, Argentina) typically exceed the guidelines for drinking water formerly established by WHO at 70 μg/L. Therefore, this study investigated the uptake of Mo in plants, using cress ( Lepidium sativum L . ) as a model using hydroponic experiments with synthetic solutions and groundwater from La Pampa. Cress grown from control experiments (150 μg/L Mo, pH 7) presented an average Mo concentration of 35.2 mg/kg (dry weight, d.w.), higher than the typical total plant range (0.7–2.5 mg/kg d.w.) in the literature. Using pooled groundwater samples (65.0–92.5 μg/L Mo) from wells of La Pampa (Argentina) as growth solutions resulted in significantly lower cress Mo levels (1.89–4.59 mg/kg d.w.) than were obtained for synthetic solutions of equivalent Mo concentration. This may be due to the high levels in these groundwater samples of As, V, Fe and Mn which are known to be associated with volcanic deposits. This research addressed the hitherto scarcity of data about the effect of various physicochemical parameters on the uptake of Mo in plants.

MARINE DIANA, Maria José Farré, Josep Sanchís, Rakesh Kanda, Monica Felipe-Sotelo, THOMAS BOND (2022)The formation of furan-like disinfection byproducts from phenolic precursors, In: Environmental science Water research & technology Royal Society of Chemistry

In this study, it was hypothesised that UV-absorbing disinfection byproducts (DBPs) may include compounds, such as halofuranones, prioritized as candidates for explaining the increased risk of bladder cancer associated with the consumption of chlorinated water highlighted by epidemiological studies. Hence, UV spectroscopy was used as a screening method to identify conditions forming stable UV-absorbing DBPs from 10 phenolic precursors at various pH levels, chlorine and bromide doses. Subsequently, high performance liquid chromatography coupled to high resolution mass spectrometry (OrbitrapTM) was used to elucidate the chemical formulas of 30 stable DBPs, 12 of which were tentatively identified as furan-like structures, including trichlorofuran-2-carboxylic acid, dichlorofuran-2-carboxylic acid, 3,4-dichlorofuran-2,5-dicarbaldehyde, 4-chloro-5-(dichloromethyl)furan-2,3-dione, 5-formyl-2-furancarboxylic acid, chloro-5-methyl-2-furancarboxylic acid, 2-acetylchlorofuran-5-one and bromo-2-furancarboxylic acid. Eleven of the furan-like structures are previously unknown as DBPs. A novel pathway was proposed to explain their formation, involving the opening of the oxidised phenolic ring followed by the formation of a 5-membered ring by intramolecular nucleophilic addition. Of the 12 furan-like DBPs identified, eight and three were respectively predicted to be mutagens and bladder carcinogens, using a quantitative structure-activity relationship theoretical model. The findings indicate the formation of furan-like DBPs from natural organic matter surrogates is more widespread than previously appreciated. Moreover, this class of DBPs may be toxicologically significant for the urinary bladder.

Jia Xiong, Fernanda V. Matta, Mary Grace, Mary Ann Lila, Neil I. Ward, Monica Felipe-Sotelo, Debora Esposito (2020)Phenolic content, anti-inflammatory properties, and dermal wound repair properties of industrially processed and non-processed acai from the Brazilian Amazon, In: Food & Function The Royal Society of Chemistry

Acai fruit is recognized for its health promoting properties. However, there is still a need to address the effects of industrial processing on this fruit. In this study, phenolic content, anti-inflammatory properties and dermal wound repair properties of 20 acai samples, before and after industrial processing, from various Amazon regions were investigated. Acai pulp was rich in total phenolics (18.9–58.8 mg g−1) and proanthocyanins (9.8–43.1 mg g−1), but contained trace anthocyanins (up to 0.1 mg g−1). Industrially processed samples lost substantial amounts of proanthocyanidins (up to 83.2%), while the anthocyanins inherently present were greatly enriched after processing (20-fold higher). Non-processed acai pulp extracts protected against early inflammation response which was correlated with proanthocyanidins, by significantly inhibiting nitric oxide production and suppressing pro-inflammatory gene expression including interleukin-1β, cyclooxygenase-2, nitric oxide synthase, and interleukin-6. The promotion of dermal wound repair of acai seed and pulp extracts was mainly contributed by anthocyanins and other bioactive compounds. The anti-inflammatory effect was diminished but wound healing effect was retained after pulp processing, suggesting the processing technology needs to be improved to maintain biological properties of acai fruit.

Monica Felipe-Sotelo, J. Hinchliff, D. Drury, N.D.M. Evans, David Read (2022)Cellulose degradation products and high ionic strength enhance the retardation of strontium in hydrated cement paste, In: Frontiers in nuclear engineering

The present concept for the disposal of some low- and all intermediate-level radioactive waste in the United Kingdom involves grouting with cement in steel drums and placement in a geological facility. The vaults would then be backfilled with low strength, high porosity cement-based materials designed to promote a pervasive, alkaline environment in which many of the radioactive species present are sparingly soluble. This work investigates the interaction of strontium with such a backfill under both diffusive and advective conditions given the potential significance of the fission product 90Sr. An important characteristic of the United Kingdom waste inventory is the abundance of organic compounds, including cellulosic materials; consequently, the experiments were repeated with products of alkaline cellulose degradation. Additional experiments were performed at high ionic strength simulating anticipated changes in the salinity of the groundwater. The effective diffusivity (De) of strontium in the absence of the organic compounds ranged between 5.5 × 10−11 and 8.5 × 10−11 m2 s−1, with a distribution coefficient (Rd) of between 2.8 × 10−3 and 3.1 × 10−3 m3 kg−1. The presence of organic compounds and/or an increase of ionic strength enhanced the retardation of strontium. The results indicate that the retention of strontium by hydrated cement paste occurs via a reversible ion exchange mechanism rather than mineralisation and is promoted by decalcification of the calcium silicate hydrate phases.

Marine Diana, Monica Felipe-Sotelo, Tom Bond (2019)Disinfection byproducts potentially responsible for the association between chlorinated drinking water and bladder cancer: a review, In: Water Research162pp. 492-504 Elsevier

Epidemiological studies have consistently associated the consumption of chlorinated drinking water with an enhanced risk of bladder cancer. While this suggests that some disinfection byproducts (DBPs) are bladder carcinogens, causal agents are unknown. This study aims to highlight likely candidates. To achieve this, structures ofknown and hypothesised DBPs werecompared with 76 known bladder carcinogens. The latter are dominated by nitrogenous and aromatic compounds; only 10 are halogenated. Under 10% of the chlorine applied during drinking water treatment is converted into identified halogenated byproducts; most of the chlorine is likely to be consumed during the generation of unidentified non-halogenated oxidation products. Six nitrosamines are among the nine most potent bladder carcinogens, and two of them are known to be DBPs: N-nitrosodiphenylamine and nitrosodibutylamine. However, these and other nitrosamines are formed in insufficiently low concentrations in chlorinated drinking water to account for the observed bladder cancer risk. Furthermore, although not proven bladder carcinogens, certain amines, haloamides, halocyclopentenoic acids, furans and haloquinones are potential candidates. At present, most identified bladder carcinogens are nitrogenous, whereas > 90% of natural organic matter is not. Therefore, non-nitrogenous DBPs are likely to contribute to the bladder cancer risk. Given the high proportion of DBPs that remains uncharacterised, it is important that future research prioritises compounds believed to be potent toxicants.

Monica Felipe-Sotelo, J Hinchliff, LP Field, AE Milodowski, O Preedy, David Read (2017)Retardation of uranium and thorium by a cementitious backfill developed for radioactive waste disposal, In: Chemosphere179pp. 127-138 Elsevier

The solubility of uranium and thorium has been measured under the conditions anticipated in a cementitious, geological disposal facility for low and intermediate level radioactive waste. Similar solubilities were obtained for thorium in all media, comprising NaOH, Ca(OH)2 and water equilibrated with a cement designed as repository backfill (NRVB, Nirex Reference Vault Backfill). In contrast, the solubility of U(VI) was one order of magnitude higher in NaOH than in the remaining solutions. The presence of cellulose degradation products (CDP) results in a comparable solubility increase for both elements. Extended X-ray Absorption Fine Structure (EXAFS) data suggest that the solubility-limiting phase for uranium corresponds to a becquerelite-type solid whereas thermodynamic modelling predicts a poorly crystalline, hydrated calcium uranate phase. The solubility-limiting phase for thorium was ThO2 of intermediate crystallinity. No breakthrough of either uranium or thorium was observed in diffusion experiments involving NRVB after three years. Nevertheless, backscattering electron microscopy and microfocus X-ray fluorescence confirmed that uranium had penetrated about 40µm into the cement, implying active diffusion governed by slow dissolution-precipitation kinetics. Precise identification of the uranium solid proved difficult, displaying characteristics of both calcium uranate and becquerelite.

Matthew Isaacs, John Hinchliff, Monica Felipe-Sotelo, David Read (2017)Factors affecting the suitability of superplasticiser-amended cement for the encapsulation of radioactive waste, In: Advances in Cement Research1700099pp. 1-15 Thomas Telford (ICE Publishing)

Organic superplasticisers improve the flow properties of cement, offering operational advantages for the disposal of radioactive wastes. However, there are concerns that they could increase the mobility of encapsulated contaminants significantly. The effect of polycarboxylate ether superplasticisers on the solubility of Ni(II), Am(III), Pu(IV) and U(VI) in two cement-equilibrated waters (ordinary Portland cement/pulverised fuel ash (OPC/PFA) and OPC/ground granulated blast-furnace slag (GGBS)) has been assessed. The study included four commercial superplasticisers, three adjuncts (a de-foaming agent, biocide and viscosity modifier) and a bespoke, synthesised superplasticiser from which residual monomer had been removed by dialysis. The commercial products (0·5% w/w dosage) had a much greater effect on metal solubility than the dialysed equivalent, increasing solubility by 2–3 orders of magnitude. As the adjuncts alone showed no effect, the difference between the commercial and synthesised superplasticisers is attributed to small molecules, primarily residual monomers, in the commercial formulations owing to incomplete polymerisation. The distribution of radionuclides in hardened cement pastes corresponds closely to the distribution of superplasticiser, as shown by 14C-labelling in combination with digital autoradiography and accounting for the bleed observed for certain slag-rich formulations.

Monica Felipe-Sotelo, J. Hinchliff, N.D.M. Evans, D. Read (2016)Solubility constraints affecting the migration of selenium through the cementitious backfill of a geological disposal facility, In: Journal of Hazardous Materials305pp. 21-29 Elsevier

This work presents the study of the solubility of selenium under cementitious conditions and its diffusion, as SeO32−, through monolithic cement samples. The solubility studies were carried out under alkaline conditions similar to those anticipated in the near-field of a cement-based repository for low- and intermediate-level radioactive waste. Experiments were conducted in NaOH solution, 95%-saturated Ca(OH)2, water equilibrated with a potential backfill material (Nirex reference vault backfill, NRVB) and in solutions containing cellulose degradation products, with and without reducing agents. The highest selenium concentrations were found in NaOH solution. In the calcium-containing solutions, analysis of the precipitates suggests that the solubility controlling phase is Ca2SeO3(OH)2·2H2O, which appears as euhedral rhombic crystals. The presence of cellulose degradation products caused an increase in selenium concentration, possibly due to competitive complexation, thereby, limiting the amount of calcium available for precipitation. Iron coupons had a minor effect on selenium solubility in contrast to Na2S2O4, suggesting that effective reduction of Se(IV) occurs only at Eh values below −300 mV. Radial through-diffusion experiments on NRVB and in a fly ash cement showed no evidence of selenium breakthrough after one year. However, autoradiography of the exposed surfaces indicated that some migration had occurred and that selenium was more mobile in the higher porosity backfill than in the fly ash cement.

Elsje Van Es, J. Hinchliff, Monica Felipe-Sotelo, A.E. Milodowski, L.P. Field, N.D.M. Evans, David Read (2015)Retention of chlorine-36 by a cementitious backfill, In: Mineralogical Magazine79(06)pp. 1297-1305 The Mineralogical Society of Great Britain and Ireland

Radial diffusion experiments have been carried out to assess the migration of 36Cl, as chloride, through a cementitious backfill material. Further experiments in the presence of cellulose degradation products were performed to assess the effect of organic ligands on the extent and rate of chloride diffusion. Results show that breakthrough of 36Cl is dependent on chloride concentration: as the carrier concentration increases, both breakthrough time and the quantity retained by the cement matrix decreases. Experiments in the presence of cellulose degradation products also show a decrease in time to initial breakthrough. However, uptake at various carrier concentrations in the presence of organic ligands converges at 45% of the initial concentration as equilibrium is reached. The results are consistent with organic ligands blocking sites on the cement that would otherwise be available for chloride binding, though further work is required to confirm that this is the case. Post-experimental digital autoradiographs of the cement cylinders, and elemental mapping showed evidence of increased 36Cl activity associated with black ash-like particles in the matrix, believed to correspond to partially hydrated glassy calcium-silicate-sulfate-rich clinker.

Maisarah Jaafar, AL Marcilla, Monica Felipe-Sotelo, Neil Ward (2017)Effect of food preparation using naturally-contaminated groundwater from La Pampa, Argentina: Estimation of elemental dietary intake from rice and drinking water, In: Food Chemistry246pp. 258-265 Elsevier

Water from La Pampa, Argentina, was used for washing and cooking rice to examine the in-situ impact of using naturally-contaminated water for food preparation on the elemental dietary intake. Whilst washing with the control tap water (28 g/L As) reduced the concentration of As in rice by 23%, the use of different well waters (281-1144 g/L) increased As levels significantly (48-227%) in comparison with the original concentration in the rice (0.056 µg/g). Cooking the rice at a low water-to-rice ratio (2:1) using modern methods increased the levels of As in the cooked samples by 2-3 orders of magnitude for both pre-washed and un-washed rice. Similar trends were observed for vanadium. Although the levels of manganese, iron, copper, zinc and molybdenum in rice were reduced during washing and cooking for most water samples, the molybdenum concentration in the cooked rice doubled (2.2-2.9 µg/g) when using water containing >1 mg/L Mo.

Monica Felipe-Sotelo, M. Edgar, T. Beattie, P. Warwick, N.D.M. Evans, David Read (2015)Effect of anthropogenic organic complexants on the solubility of Ni, Th, U(IV) and U(VI), In: Journal of Hazardous Materials300pp. 553-560

The influence of anthropogenic organic complexants (citrate, EDTA and DTPA from 0.005 to 0.1 M) on the solubility of nickel(II), thorium(IV) and uranium (U(IV) and U(VI)) has been studied. Experiments were carried out in 95%-saturated Ca(OH)2 solutions, representing the high pH conditions anticipated in the near field of a cementitious intermediate level radioactive waste repository. Results showed that Ni(II) solubility increased by 2–4 orders of magnitude in the presence of EDTA and DTPA and from 3 to 4 orders of magnitude in the case of citrate. Citrate had the greatest effect on the solubility of Th(IV) and U(IV)/(VI). XRD and SEM analyses indicate that the precipitates are largely amorphous; only in the case of Ni(II), is there some evidence of incipient crystallinity, in the form of Ni(OH)2 (theophrastite). A study of the effect of calcium suggests that U(VI) and Ni(II) may form metal-citrate-OH complexes stabilised by Ca2+. Thermodynamic modelling underestimates the concentrations in solution in the presence of the ligands for all the elements considered here. Further investigation of the behaviour of organic ligands under hyperalkaline conditions is important because of the use of the thermodynamic constants in preparing the safety case for the geological disposal of radioactive wastes.

Monica Felipe-Sotelo, E.R. Henshall-Bell, N.D.M. Evans, David Read (2015)Comparison of the chemical composition of British and Continental European bottled waters by multivariate analysis, In: Journal of Food Composition and Analysis39pp. 33-42 Elsevier

The elemental composition of 37 bottled waters from the UK and continental Europe has been determined. Ca, K, Mg, Na, Al, As, Ba, Cd, Cr, Co, Cu, Fe, Mn, Mo, Ni, Pb, Sb, Sr, U, V and Zn were determined by ICP-OES and ICP-MS, in addition to inorganic and total organic carbon. The composition of all the waters analysed fell within the guideline values recommended by the World Health Organization. Na, Ca, Sr and Ba showed the widest variation in concentrations, ranging over two orders of magnitude. Levels of Fe were below the limit of detection (30 μg L−1) in all samples analysed. Waters produced in the UK generally showed lower levels of most major elements and trace metals, with the exception of Ba (up to 455 μg L−1). Italian waters showed the highest concentrations of Sr (3000–8000 μg L−1) and U (8–13 μg L−1), whereas waters produced in Slovakia and the Czech Republic showed the highest levels of Pb (0.7–4 μg L−1). The use of multivariate analysis reveals an association between high alkaline metal content and high concentrations of As and Cr. There also appears to be a correlation between high Ca and Sr content and high levels of U. Analysis of variance (ANOVA) indicates that the composition of bottled water can be distinguished primarily by the country of origin, over other factors including the geological environment of the source. This would suggest that composition reflects, and is biased towards, consumer preferences.

Thomas Bond, V Ferrandiz-Mas, Monica Felipe-Sotelo, E van Sebille (2018)The Occurrence and Degradation of Aquatic Plastic Litter Based on Polymer Physicochemical Properties: a Review, In: Critical Reviews in Environmental Science and Technology Taylor & Francis

The whereabouts of the overwhelming majority of plastic estimated to enter the environment is unknown. This study’s aim was to combine information about the environmental occurrence and physicochemical properties of widespread polymers to predict the fate of aquatic plastic litter. Polyethylene and polypropylene are common in the surface layer and shorelines; polyester and cellulosic fibres in sewage treatment works, estuarine and deep-sea sediments. Overall, non-buoyant polymers are underrepresented on the ocean surface. Three main explanations are proposed for the missing plastic. The first is accumulation of both buoyant and non-buoyant polymers in sewage treatment works, river and estuarine sediments and along shorelines. The second is settling of non-buoyant polymers into the deep-sea. The third is fragmentation of both buoyant and non-buoyant polymers into particles smaller than captured by existing experimental methods. Some isolation techniques may overrepresent larger, buoyant particles; methodological improvements are needed to capture the full size-range of plastic litter. When microplastics fragment they become neutrally-buoyant, thus nanoplastics are potentially widely dispersed in aquatic systems, both horizontally and vertically. Ultimately, over decades or longer, plastics are potentially solubilized and subsequently biodegraded. The rates at which these processes apply to plastic litter in different environmental compartments remain largely unknown.

M. Felipe-Sotelo, J. Hinchliff, L.P. Field, A.E. Milodowski, J.D. Holt, S.E. Taylor, D. Read (2016)The solubility of nickel and its migration through the cementitious backfill of a geological disposal facility for nuclear waste, In: Journal of Hazardous Materials314pp. 211-219 Elsevier

This work describes the solubility of nickel under the alkaline conditions anticipated in the near field of a cementitious repository for intermediate level nuclear waste. The measured solubility of Ni in 95%-saturated Ca(OH)2 solution is similar to values obtained in water equilibrated with a bespoke cementitious backfill material, on the order of 5 × 10−7 M. Solubility in 0.02 M NaOH is one order of magnitude lower. For all solutions, the solubility limiting phase is Ni(OH)2; powder X-ray diffraction and scanning transmission electron microscopy indicate that differences in crystallinity are the likely cause of the lower solubility observed in NaOH. The presence of cellulose degradation products causes an increase in the solubility of Ni by approximately one order of magnitude. The organic compounds significantly increase the rate of Ni transport under advective conditions and show measurable diffusive transport through intact monoliths of the cementitious backfill material.

M. Felipe-Sotelo, M. J. Cal-Prieto, M. P. Gomez-Carracedo, J. M. Andrade, A. Carlosena, D. Prada (2006)Handling complex effects in slurry-sampling-electrothermal atomic Zn absorption spectrometry by multivariate calibration, In: Analytica chimica acta571(2)pp. 315-323 Elsevier

Analysis of solid samples by slurry-sampling-electrothermal atomic absorption spectrometry (SS-ETAAS) can imply spectral and chemical interferences caused by the large amount of concomitants introduced into the graphite furnace. Sometimes they cannot be solved using stabilized temperature platform furnace (STPF) conditions or typical approaches (previous sample ashing, use of chemical modifiers, etc.). which are time consuming and quite expensive. A new approach to handle interferences using multivariate calibrations (partial least squares, PLS, and artificial neural networks, ANN) is presented and exemplified with a real problem consisting on determining Sb in several solid matrices (soils, sediments and coal fly ash) as slurries by ETAAS. Experimental designs were implemented at different levels of Sb to develop the calibration matrix and assess which concomitants (seven ions were considered) modified the atomic signal mostly. They were Na and Ca2+- and they induced simultaneous displacement. depletion (enhancement) and broadening of the atomic peak. Here it is shown that these complex effects can be handled in a reliable. fast and cost-effective way to predict the concentration of Sb in slurry samples of several solid matrices. The method was validated predicting the concentrations of five certified reference materials (CRMs) and studying its robustness to current ETAAS problems. It is also shown that linear PLS can handle eventual non-linearities and that its results are comparable to more complex (non-linear) models, as those front ANNs. (c) 2006 Elsevier B.V. All rights reserved.

M Felipe-Sotelo, A Carlosena, E Fernández, P López-Mahía, S Muniategui, D Prada (2001)Chemical modifiers for direct determination of cobalt in coal combustion residues by ultrasonic slurry-sampling-ETAAS, In: Fresenius' journal of analytical chemistry371(8)pp. 1139-1145

Five modifiers were tested for the direct determination of cobalt in coal fly ash and slag by ultrasonic slurry-sampling electrothermal atomic absorption spectrometry (USS-ETAAS). The furnace temperature programs and the appropriate amount for each modifier were optimized to get the highest signal and the best separation between the atomic and background signals. Nitric acid (0.5% v/v) was the most adequate chemical modifier for cobalt determination, selecting 1,450 degrees C and 2,100 degrees C as pyrolysis and atomization temperatures, respectively. This modifier also acts as liquid medium for the slurry simplifying the procedure. The remaining modifiers enhanced the background signal, totally overlapped with cobalt peak. The method optimized gave a limit of detection of 0.36 microg g(-1), a characteristic mass of 13 +/- 1 pg and an overall-method precision which is highly satisfactory (

M FELIPE-SOTELO, M. J CAL-PRIETO, A Carlosena, J. M Andrade, E Femandez, D Prada (2005)Multivariate optimization for molybdenum determination in environmental solid samples by slurry extraction-ETAAS, In: Analytica chimica acta553(1-2)pp. 208-213 Elsevier
M. Felipe-Sotelo, J. Hinchliff, N. Evans, P. Warwick, D. Read (2012)Sorption of radionuclides to a cementitious backfill material under near-field conditions, In: Mineralogical magazine76(8)pp. 3401-3410 Mineralogical Society

The sorption behaviour of I (super -) , Cs (super +) , Ni (super 2+) , Eu (super 3+) , Th (super 4+) and UO (super 2+) (sub 2) on NRVB (Nirex reference vault backfill) a possible vault backfill, at pH 12.8 was studied. Sorption isotherms generated were compared to results obtained in the presence of cellulose degradation products (CDP). Whereas Cs was not affected by the presence of the organic compounds, a notable reduction in the sorption of Th and Eu to cement was observed. The results also indicated limited removal of Ni from solution (with or without an organic ligand) by sorption, the concentration in solution seemingly being determined solely by solubility processes. In the case of uranium, the presence of CDP increased the sorption to cement by almost one order of magnitude. Further studies into the uptake of CDP by cement are being undertaken to identify the mechanism(s) responsible.

N. D. M. Evans, S. Anton Gascon, S. Vines, M. Felipe-Sotelo (2012)Effect of competition from other metals on nickel complexation by alpha -isosaccharinic, gluconic and picolinic acids, In: Mineralogical magazine76(8)pp. 3425-3434 Mineralogical Society

The effect of competition from other metal ions on the complexation of Ni with isosaccharinic acid, gluconic acid and picolinic acid, at high pH, is described. The competing metal ions used were divalent Co, trivalent Eu and tetravalent Th. In the majority of cases, competition from these metal ions followed the predicted pattern, with most anomalies seeming to be caused by sorption of Ni to the many different solid phases formed in presence of the competing ions. The Ni solid phase was shown to change with time during the course of the study. No major unexplained competition effects were found.

M. J CAL-PRIETO, M FELIPE-SOTELO, A Carlosena, J. M Andrade, P LOPEZ-MAHIA, S Muniategui, D Prada (2002)Slurry sampling for direct analysis of solid materials by electrothermal atomic absorption spectrometry (ETAAS). A literature review from 1990 to 2000, In: Talanta (Oxford)56(1)pp. 1-51 Elsevier
Nick Evans, Peter Warwick, Monica Felipe-Sotelo, Sarah Vines (2012)Prediction and measurement of complexation of radionuclide mixtures by alpha-isosaccharinic, gluconic and picolinic acids, In: Journal of radioanalytical and nuclear chemistry293(3)pp. 725-730 Springer Nature

The purpose of this study was to investigate the effects of competition between cobalt, europium and strontium for isosaccharinate, gluconate and picolinate. Systems where results indicated that competitive effects were significant have been identified. Thermodynamic calculations were performed for each system for comparison with the experimental results. Some exceptions may be due to precipitation of some species, or presence of species not in databases, or formation of mixed-metal complexes, or sorption to the solid phase(s). In some of the experiments, the complexity of the systems studied caused difficulty in identifying consistent trends. By concentrating on the results for simpler systems (i.e. for solubilities in the presence and absence of organic complexants and with just one competing metal ion), the evidence for competition effects has been investigated. Evidence for solubility enhancement due to organic ligands was apparent in the data for the systems Co with gluconate and Eu with isosaccharinate and gluconate. Of these above cases, the systems in which the effects of the competing ion are consistent with competition were limited to the cases of Eu with isosaccharinate and Sr as the competing ion, and Eu with gluconate and either Co or Sr as the competing ion.

M Felipe-Sotelo, A Carlosena, E Fernández, P López-Mahía, S Muniategui, D Prada (2004)Microwave-assisted extraction and ultrasonic slurry sampling procedures for cobalt determination in geological samples by electrothermal atomic absorption spectroscopy, In: Talanta (Oxford)63(3)pp. 735-742

Slurry sampling is compared to microwave-assisted acid digestion for cobalt determination in soil/sediment samples by electrothermal atomic absorption spectrometry (ETAAS). Furnace temperature programs and appropriate amounts of three chemical modifiers were optimised in order to get the highest signals and good separations between the atomic and background signals. Using nitric acid (0.5% (v/v)) as liquid medium, no chemical modifier was needed. The detection limit, based on integrated absorbance, was 0.04mugg(-1) for digests and slurries. Within-batch precision and analytical recoveries were satisfactory for both procedures. Accuracy was tested by analysing a reference soil and a sediment from IRMM. The methods were further compared employing a set of roadside soils and estuarine sediments. As no significant differences (95% confidence) were found, practical analytical properties were suggested in order to select one of them.

M. Felipe-Sotelo, J. Hinchliff, D. Drury, N.D.M. Evans, S. Williams, D. Read (2014)Radial diffusion of radiocaesium and radioiodide through cementitious backfill, In: Physics and chemistry of the earth. Parts A/B/C70-71pp. 60-70 Elsevier Ltd

•Through-diffusion was used to study the migration of Cs and I− through cement.•Diffusion was investigated using a radial setup.•Cellulose degradation products accelerate the diffusion of Cs and I− through cement.•Autoradiography showed homogeneous distribution of Cs within the blocks.•Goldsim was used to fit the profiles and determine diffusivity and partition ratios. The function of the backfill material in a geological disposal facility (GDF) is to chemically condition the environment of the near field and thereby chemically retard the transport of the radionuclides present in the waste. This function of the backfill material is usually referred to as chemical containment. Diffusion experiments are being carried out over periods up to four years to assess the diffusion of Cs, Ni, Eu, Th, U and I (as I−) through Nirex Reference Vault Backfill (NRVB). The method uses cylinders of NRVB (40mm diameter, 40–45mm height) which can be doped via a central well with the radionuclides of interest. Diffusion occurs radially into a surrounding solution already pre-equilibrated with the cement. This paper shows the results obtained during the first two years for experiments undertaken using 137Cs and 125I− tracers with and without carrier. Comparison is made to tritiated water under identical experimental conditions. Breakthrough of Cs and I− occurred within the first week of the experiments, reaching steady state in the surrounding solution after 20–50days. The maximum concentrations expected from the original inventories based on a simple dilution calculation have not been reached, indicating that retention in the matrix has occurred; ranging from 10% to 40% for Cs, and up to 50% for I−. Corresponding experiments using a solution containing cellulose degradation products (CDP) showed an increased diffusion for both Cs and I. Migration profiles have been obtained and the relative retention of each radionuclide has been confirmed using digital autoradiography. The results indicate that, for both isotopes, migration occurs through the cement matrix rather than through microfissures. However, whereas Cs is homogeneously distributed within the blocks, there is evidence of zones of preferential I− accumulation even where concentrations in solution have reached steady state. Transport modelling using GoldSim has replicated experimental observations, producing comparable partition ratios (Rd) to those reported in the literature.

The presence of organochlorine compounds (OCs)-namely hexachlorobenzene (HCB), hexachlorocyclohexanes (HCH), polychlorobiphenyls (PCBs #28, 52, 101, 118, 138, 153 and 180), dichlorodiphenyltrichloroethane (DDT) and dichlorodiphenyldichloroethane (DDE)-was examined in various fish tissues (muscle and liver) sampled in 23 mountain lakes in Europe. The dependence of these organochlorine compounds on geographical parameters (altitude, longitude, latitude and temperature) and physiological parameters (lipid content, age, weight and size) was assessed. Principal components analysis (PCA) and partial least squares (PLS) models were used for the analyses. PCA results showed that organochlorine compound concentrations in fish tissues increased with increasing altitude and decreasing temperatures. This trend appeared to be more marked for the less volatile compounds. Some differences were found between the muscle and liver in the effects of the percentage of lipids on the accumulation of organochlorine compounds and the behaviour of HCB, Moreover, PCBs tended to accumulate more in liver rather than in muscle. PCA scores clearly differentiated samples according to the lake of origin. PLS models confirmed that temperature and altitude were the main factors influencing the accumulation of most organochlorine compounds in the lipids of the fish tissue. (C) 2008 Elsevier B.V. All rights reserved.

M. Felipe-Sotelo, A. Carlosena, E. Fernández-Fernández, S. Muniategui, P. López-Mahı́a, D. Prada (2004)Evaluation of two atomisation modes for direct determination of molybdenum in complex matrices by ultrasonic slurry sampling–electrothermal atomic absorption spectrometry, In: Analytica chimica acta524(1)pp. 329-337 Elsevier B.V

Tube wall (TWA) and L’vov platform (LPA) atomisations were compared for the direct determination of molybdenum (Mo) in coal fly ash by slurry sampling–electrothermal atomic absorption spectrometry (ETAAS). For both atomisation modes eight chemical modifiers were tested, namely HNO 3, Pd(NO 3) 2, Mg(NO 3) 2, Pd + Mg(NO 3) 2, reduced Pd, BaF 2, Ir and HF. The interfering effects of major and minor concomitants of samples on Mo signals and memory effects were also evaluated. BaF 2 and Pd(NO 3) 2 + Mg(NO 3) 2 mixture were selected for TWA and LPA, respectively. Standard addition calibration is needed in both cases. The best peak performance, memory effect reduction, within-run precision (6% versus 9% R.S.D.), and sensitivity ( m o = 7.5 pg versus 15.2 pg) were achieved with TWA compared to LPA. Both atomisation modes gave good analytical recoveries (94–102%), but the analysis of a certified coal fly ash (NIST SRM 1633a) only was accurate using TWA. Additionally, the urban dust NIST SRM 1629a was analysed.

M. Felipe-Sotelo, J.M. Andrade, A. Carlosena, R. Tauler (2007)Temporal characterisation of river waters in urban and semi-urban areas using physico-chemical parameters and chemometric methods, In: Analytica chimica acta583(1)pp. 128-137 Elsevier B.V

Three sampling campaigns were carried out in rivers located at two hydrographic basins affected by urban and semi-urban areas around the Metropolitan area of A Coruña (ca. 500,000 inhabitants, NW-Spain) to study local and temporal variations of 21 physicochemical parameters (pH, conductivity, Cl −, SO 4 2−, SiO 2, Ca 2+, Mg 2+, Na +, K +, hardness, NO 3 −, NO 2 −, NH 4 +, COD, PO 4 3−, Zn 2+, Cu 2+, Mn 2+, Pb 2+, alkalinity and acidity) in 23 sampling points. The temporal evolution of the water quality was assessed by matrix augmentation principal components analysis (MA-PCA) and parallel factor analysis (PARAFAC). Moreover, classical principal components analysis (PCA) (one per sampling campaign) was applied with exploratory and comparison purposes. The first factor of the different studies comprised variables associated to the mineral content and it differentiated the samples according to their hydrographic basins. The second factor was mainly associated to organic matter, from domestic wastes and decomposition of natural debris. The temporal evolution of the water quality was mostly related to seasonal increments of the physicochemical parameters defining the decomposition of the organic matter. The three models applied (PCA, MA-PCA and PARAFAC) led to similar conclusions, nonetheless, MA-PCA excelled, since the refolding of scores provided more straightforward and convenient overview of sample time and geographical variations than individual PCA and it is more flexible and adaptable to environmental studies than PARAFAC.

M FELIPE-SOTELO, A Carlosena, J. M Andrade, E Fernandez, P LOPEZ-MAHIA, S Muniategui, D Prada (2004)Development of a slurry-extraction procedure for direct determination of cobalt by electrothermal atomic absorption spectrometry in complex environmental samples, In: Analytica chimica acta522(2)pp. 259-266 Elsevier
M FELIPE-SOTELO, J. M Andrade, A Carlosena, D Prada (2003)Partial least squares multivariate regression as an alternative to handle interferences of Fe on the determination of trace Cr in water by electrothermal atomic absorption spectrometry, In: Analytical chemistry (Washington)75(19)pp. 5254-5261 American Chemical Society
M. Felipe-Sotelo, Antoni E. Milodowski, Nicholas D. M. Evans (2015)Inhibition of the formation and stability of inorganic colloids in the alkaline disturbed zone of a cementitious repository, In: Mineralogical magazine79(6)pp. 1419-1431 Mineralogical Society

The generation and stability of inorganic colloids have been studied under hyperalkaline conditions. For the generation of colloids, intact cores of Bromsgrove Sandstone were flushed with simulated cement leachates, and the eluates were ultrafiltered sequentially (12 mu m, 1 mu m, 0.1 mu m and 30 kDa) for the separation of any colloids found. No colloid formation was observed during the experiments; however the analysis by ICP-MS of the eluates showed significant increases in Si and Al, indicating silicate mineral dissolution, as well as reduction of the concentration of Ca in the leachates indicating precipitation of secondary Ca-rich phases. Flow experiments with cement leachates spiked with tritiated water showed a noticeable reduction of the porosity of the sandstone as well as changes in the pore distribution. Additional stability experiments were carried out using model silica and Fe (sub 2) O (sub 3) colloids. The experiments indicated that the stability of the colloids was mainly controlled by the concentration of Ca in solution and that both types were unstable under the chemical conditions in the alkaline disturbed zone. The presence of cement additives such as superplasticisers could enhance the stability of the colloids.

Katherine Lawrence, Fengjie Xia, Rory L. Arrowsmith, Haobo Ge, Geoffrey W. Nelson, John S. Foord, Monica Felipe-Sotelo, Nick D. M. Evans, John M. Mitchels, Stephen E. Flower, Stanley W. Botchway, Daniel Wolverson, Gazi N. Aliev, Tony D. James, Sofia I. Pascu, Frank Marken (2014)Hydrothermal Conversion of One-Photon-Fluorescent Poly(4-vinylpyridine) into Two-Photon-Fluorescent Carbon Nanodots, In: Langmuir30(39)pp. 11746-11752 Amer Chemical Soc

A novel two-photon-fluorescent N,O-heteroatom-rich carbon nanomaterial has been synthesized and characterized. The new carbon nanoparticles were produced by hydrothermal conversion from a one-photon-fluorescent poly(4-vinylpyridine) precursor (P4VP). The carbonized particles (cP4VP dots) with nonuniform particle diameter (ranging from sub-6 to 20 nm with some aggregates up to 200 nm) exhibit strong fluorescence properties in different solvents and have also been investigated for applications in cell culture media. The cP4VP dots retain their intrinsic fluorescence in a cellular environment and exhibit an average excited-state lifetime of 2.0 +/- 0.9 ns in the cell. The cP4VP dots enter HeLa cells and do not cause significant damage to outer cell membranes. They provide one-photon or two-photon fluorescent synthetic scaffolds for imaging applications and/or drug delivery.

M. Alier, M. Felipe-Sotelo, I. Hernandez, R. Tauler (2009)Variation patterns of nitric oxide in Catalonia during the period from 2001 to 2006 using multivariate data analysis methods, In: Analytica chimica acta642(1-2)pp. 77-88 Elsevier

Multivariate data analysis methods are applied to study of the geographical and temporal distribution of nitric oxide (NO) in Catalonia (North-East Spain), measured during the period 2001-2006 in 50 sampling stations. Principal component analysis (PCA) and Multivariate Curve Resolution Alternating Least Squares (MCR-ALS) were applied for that purpose. The simultaneous analysis of NO data from sampling stations showed that its geographical distribution was rather uniform during the period considered. When three individual sampling stations were considered (two urban sites and one rural location), three different temporal patterns were resolved, with marked daily-night changes mainly attributed to traffic and also, important winter-summer seasonal variations. A decreasing trend in the levels of NO has been also observed in recent years. Comparison with nitrogen dioxide (NO2) profiles shows that the daily variation is quite similar to the NO variation, however NO2 displays very little oscillations along the seasons and no reduction of its concentration was observed in the last years, contrasting with NO tendencies. The use of MCR-ALS is confirmed to be a useful method to improve interpretability in atmospheric contamination studies. The use of non-negativity and trilinearity constraints is shown to provide improved interpretations of the different contamination patterns in environmental terms. (C) 2009 Elsevier B.V. All rights reserved.

Giselaine A. Santos, Alexandrina A. C. Carvalho, Aline P. Oliveira, Juliana Naozuka, Fernanda Matta, Monica Felipe-Sotelo, Neil Ward, Nadia C. F. Correa, Cassiana S. Nomura (2021)Bioaccessibility of Essential Elements in Acai (Euterpe oleracea Mart.) Pulp, In: ACS food science & technology1(5)pp. 874-883 Amer Chemical Soc

Acai consumption has been increasing due to the health benefits associated with the levels of essential elements and bioactive compounds, such as phenols and flavonoids. However, any nutritional information needs to go beyond that for total elemental levels, and elemental bioaccessibility data for this food should also be highlighted. In this study, the bioaccessibility of essential elements in two different genotypes of acai pulp (white and purple) was evaluated. The in vitro gastrointestinal digestion of acai pulp followed by elemental determination using inductively coupled plasma optical emission spectrometry (ICP OES) was performed to evaluate the bioaccessibility of Ca, Cu, Fe, K, Mg, Mn, P, and Zn. The total elemental concentrations for purple and white acai pulp were found to not be significantly different between the genotypes. Most of the elements studied showed high levels of bioaccessibility, with values greater than 70%, apart from Fe in purple acai, which had the lowest bioaccessibility level.

M Felipe-Sotelo, M J Cal-Prieto, J Ferre, R Boque, J M Andrade, A Carlosena (2006)Linear PLS regression to cope with interferences of major concomitants in the determination of antimony by ETAAS, In: Journal of analytical atomic spectrometry21(1)pp. 61-68 Royal Soc Chemistry

Most heavy metals are present in trace concentrations in mail), matrices whereas concomitants are, generally, several orders of magnitude higher. Thus, when Sb was determined in water samples by electrothermal atomic absorption spectrometry (ETAAS),, typical major concomitant ions Ca2+, Fe3+, Na+, Mg2+, Cl-, PO43- and SO42- induced displacement, depletion and division of its atomic peak. These interferences were handled with partial least squares regression (PLS). Plackett-Burman experimental designs were implemented to develop the calibration matrix and assess which concomitants modified the atomic signal the most. Despite the concentration-dependent effects induced by the concomitants, linear PLS was a reliable way to predict the concentration of Sb in aqueous samples (standard error of prediction = 1.44 ng mL(-1)). Polynomial PLS regression was also studied but it did not outperform the linear models. The multivariate-derived figures of merit were calculated: sensitivity (0.014 absorbance/(ng mL(-1))), characteristic mass (6.2 pg) and selectivity (using the net analyte signal concept, 83%); limit of detection (considering 5% of type-alpha and type-beta risks, 5.6 ng mL(-1)) and quantification (10.6 ng mL(-1)), following recent IUPAC and ISO guidelines. The method was validated studying its robustness to current ETAAS problems and analysing several certified reference waters.

Katherine Lawrence, Geoffrey W. Nelson, John S. Foord, Monica Felipe-Sotelo, Nick D. M. Evans, John M. Mitchels, Tony D. James, Fengjie Xia, Frank Marken (2013)"Hydrothermal wrapping" with poly(4-vinylpyridine) introduces functionality: pH-sensitive core-shell carbon nanomaterials, In: Journal of materials chemistry. A, Materials for energy and sustainability1(14)pp. 4559-4564 Royal Soc Chemistry

Negatively charged carbon nanoparticles (surface-phenylsulfonated) are "wrapped" in a poly(4-vinylpyridine) cationomer and hydrothermally converted into a pH-responsive core-shell nano-composite. With a "thin shell" this nano-material (ca. 20-40 nm diameter) is water-insoluble but readily dispersed into ethanol and deposited onto electrodes. Zeta-potential measurements suggest a point of zero charge (PZC) at ca. pH 4.5 with negative functional groups dominating in the more alkaline range and positive functional groups dominating in the acidic range. XPS data suggest carboxylate and pyridinium-like functional groups. This is further confirmed in voltammetric measurements for adsorbed cations (methylene blue) and adsorbed anions (indigo carmine). The specific capacitance reaches a maximum of 13 F g(-1) at the PZC explained here tentatively by a "shell charging" effect within the nanoparticle shell.

M Felipe-Sotelo, A Carlosena, J M Andrade, M J Cal-Prieto, E Fernandez, D Prada (2005)Slurry-based procedures to determine chromium, nickel and vanadium in complex matrices by ETAAS, In: Microchemical journal81(2)pp. 217-224 Elsevier

Two slurry-based ETAAS methodologies are compared to determine directly Cr, Ni and V in coal fly ash, soils and sediments: current slurry analysis (USS) and 'slurry extraction' (SE). Slurries for USS-ETAAS were prepared in 0.5% HNO3. HF and HNO3 were evaluated as chemical modifiers. HF was the extractant for the SE-ETAAS approach. A unique slurry-based procedure to measure Cr, Ni and V could not be established. Cr concentrations up to 100 mu g g(-1) were accurately determined by USS (0.5% HNO3; lambda = 429.0 nm; LOD = 0.35 mu g g(-1)) whereas higher contents required the SE procedure (sample grinding, 30% HF; LOD = 0.02 mu g g(-1)). Both methods were appropriate to determine Ni (LOD = 0.11 and 0.08 mu g g(-1), for USS and SE, respectively). V was satisfactorily quantified only with the USS approach (LOD=0.80 mu g g(-1)). (c) 2005 Elsevier B.V All rights reserved.

Mónica Felipe-Sotelo, L. Gustems, I. Hernández, Marta Terrado Casanovas, Romà Tauler (2006)Investigation of geographical and temporal distribution of tropospheric ozone in Catalonia (North-East Spain) during the period 2000–2004 using multivariate data analysis methods, In: Atmospheric environment (1994)40(38)pp. 7421-7436 Elsevier

16 pages, 6 figures, 1 table.-- Printed version published Dec 2006. Multivariate data analysis methods were applied to study the geographical and temporal distribution of tropospheric ozone in Catalonia (North-East Spain). Ozone data were collected during the period 2000–2004 in 41 sampling stations. Data analysis by multivariate curve resolution alternating least squares (MCR-ALS) allowed the recognition of three sub-regions within Catalonia according to their ozone variation patterns. Representation of loadings by means of geographical information systems (GIS) allowed a better visualisation of these areas. Daily, weekly and annual ozone profiles were determined for each sub-region. Principal component analysis (PCA) was applied within each sub-region to unravel the relationship between ozone variation and some other parameters, such as atmospheric pollutants (SO2, H2S, NO, NO2, CO and particulate matter), as well as meteorological variables (temperature, relative humidity, solar radiation, pressure, precipitation and wind speed. M. Felipe-Sotelo acknowledges CSIC for the awarding of an I3P research grant, co-funded by the European Social Fund (EU). Peer reviewed

Claire Davison, Dany Beste, Melanie Bailey, Mónica Felipe-Sotelo (2023)Expanding the boundaries of atomic spectroscopy at the single-cell level: critical review of SP-ICP-MS, LIBS and LA-ICP-MS advances for the elemental analysis of tissues and single cells, In: Analytical and bioanalytical chemistry Springer

Metals have a fundamental role in microbiology, and accurate methods are needed for their identification and quantification. The inability to assess cellular heterogeneity is considered an impediment to the successful treatment of different diseases. Unlike bulk approaches, single-cell analysis allows elemental heterogeneity across genetically identical populations to be related to specific biological events and to the effectiveness of drugs. Single particle-inductively coupled plasma-mass spectrometry (SP-ICP-MS) can analyse single cells in suspension and measure this heterogeneity. Here we explore advances in instrumental design, compare mass analysers and discuss key parameters requiring optimisation. This review has identified that the effect of pre-treatment of cell suspensions and cell fixation approaches require further study and novel validation methods are needed as using bulk measurements is unsatisfactory. SP-ICP-MS has the advantage that a large number of cells can be analysed; however, it does not provide spatial information. Techniques based on laser ablation (LA) enable elemental mapping at the single-cell level, such as laser-induced breakdown spectroscopy (LIBS) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). The sensitivity of commercial LIBS instruments restricts its use for sub-tissue applications; however, the capacity to analyse endogenous bulk components paired with developments in nano-LIBS technology shows great potential for cellular research. LA-ICP-MS offers high sensitivity for the direct analysis of single cells, but standardisation requires further development. The hyphenation of these trace elemental analysis techniques and their coupling with multi-omic technologies for single-cell analysis have enormous potential in answering fundamental biological questions.

Fernanda V Matta, Jia Xiong, Mary Ann Lila, Neil I Ward, Mónica Felipe-Sotelo, Debora Esposito (2020)Chemical Composition and Bioactive Properties of Commercial and Non-Commercial Purple and White Açaí Berries, In: Foods9(10) MDPI

Chemical composition analysis of açaí extracts revealed higher levels of total polyphenol content in purple açaí samples for both commercial (4.3–44.7 gallic acid equivalents mg/g) and non-commercial samples (30.2–42.0 mg/g) compared to white (8.2–11.9 mg/g) and oil samples (0.8–4.6 mg/g). The major anthocyanin compounds found in purple açaí samples were cyanidin-3-glucoside and cyanidin-3-rutinoside with total concentrations in the range of 3.6–14.3 cyanidin-3-glucoside equivalents mg/g. The oligomeric proanthocyanidins were quantified in the range of 1.5–6.1 procyanidin B1 equivalents mg/g. Moreover, açaí presented significant levels of calcium, magnesium, manganese, iron, zinc and copper, essential minor and trace elements, in comparison with other berries. All of the açaí extracts at 50 μg/mL potently inhibited the release of reactive oxygen species in lipopolysaccharide-stimulated RAW 264.7 murine macrophage cells, but none inhibited the release of nitric oxide. Furthermore, all the açaí samples demonstrated potential as wound healing agents due to the high levels of migration activity in human fibroblast cells.

ATHANASIOS NIKOLAOU, MONICA FELIPE-SOTELO, ROBERT ANDREW DOREY, Jorge Gutierrez-Merino, DANIELA CARTA (2022)Silver-doped phosphate coacervates to inhibit pathogenic bacteria associated with wound infections: an in vitro study, In: Scientific reports1210778 Nature

There is a great demand from patients requiring skin repair, as a result of poorly healed acute wounds or chronic wounds. These patients are at high risk of constant inflammation that often leads to life-threatening infections. Therefore, there is an urgent need for new materials that could rapidly stimulate the healing process and simultaneously prevent infections. Phosphate-based coacervates (PC) have been the subject of increased interest due to their great potential in tissue regeneration and as controlled delivery systems. Being bioresorbable, they dissolve over time and simultaneously release therapeutic species in a continuous manner. Of particular interest is the controlled release of metallic antibacterial ions (e.g. Ag+), a promising alternative to conventional treatments based on antibiotics, often associated with antibacterial resistance (AMR). This study investigates a series of PC gels containing a range of concentrations of the antibacterial ion Ag+ (0.1, 0.3 and 0.75 mol%). Dissolution tests have demonstrated controlled release of Ag+ over time, resulting in a significant bacterial reduction (up to 7 log), against both non-AMR and AMR strains of both Gram-positive and Gram-negative bacteria (Staphylococcus aureus, Enterococcus faecalis, Escherichia coli and Pseudomonas aeruginosa). Dissolution tests have also shown controlled release of phosphates, Ca2+, Na+ and Ag+ with most of the release occurring in the first 24 h. Biocompatibility studies, assessed using dissolution products in contact with human keratinocyte cells (HaCaT) and bacterial strains, have shown a significant increase in cell viability (p ≤ 0.001) when gels are dissolved in cell medium compared to the control. These results suggest that gel-like silver doped PCs are promising multifunctional materials for smart wound dressings, being capable of simultaneously inhibit pathogenic bacteria and maintain good cell viability.