Automated flow systems for total and isotopic analysis of thorium and uranium in samples of environmental interest

Tenint en compte, les característiques i la presència d’urani i tori al medi ambient, així com la evolució de les directives que estipulen els nivells màxims de materials radioactius al medi ambient, en aquesta tesis es presenten dues revisions exhaustives i quatre mètodes analítics per a la determinació total e isotòpica de tori i urani, com alternatives a les separacions radioquímiques clàssiques, que es caracteritzen per ser laborioses i de llarga duració. Aquestes metodologies varen ser automatitzades mitjançant l’ús de tècniques d’anàlisis en flux multiconmutades, les quals proporcionen un important estalvi de reactius, amb la conseqüent reducció de cost per anàlisis i de generació de residus permetent una major freqüència d’anàlisis, i una mínima manipulació de les mostres. La espectrofotometria de llarg pas òptic i la espectrometria de masses de plasma acoblat inductivament (ICP-MS) varen ser les tècniques de detecció emprades en els mètodes desenvolupats com alternatives a detectors radiomètrics.Taking into account the occurrence, the characteristics of uranium and thorium in the environment as well as the evolution of the directives which stipulate the limit values of radioactive materials in water samples, in this thesis two comprehensive reviews and four automated analytical systems for total and isotopic thorium and uranium determination are presented as alternatives to classical radiochemical separations which are laborious and time consuming. These methodologies have been automated exploiting multicommutated flow techniques, which provide minimal sample handling, low reagent consumption and waste generation and a high frequency of analysis. Long path length spectrophotometry and ICP-MS have been implemented in the developed methods as detection techniques instead of radiometric detectors in order to obtain fully automated, low cost and fast thorium and uranium analyzers. All the developed methods proposed in this thesis have been satisfactorily applied to environmental samples and have been validated with reference material

Fully automated lab-on-valve-multisyringe flow injection analysis-ICP-MS system: An effective tool for fast, sensitive and selective determination of thorium and uranium at environmental levels exploiting solid phase extraction

An on-line solid-phase extraction method linked to inductively coupled mass spectrometry (ICP-MS) has been developed for the determination of low levels of uranium and thorium in environmental samples. The hyphenation of lab-on-valve (LOV) and multisyringe flow injection analysis (MSFIA), coupled to an ICP-MS, allows the simultaneous determination of thorium and uranium in different types of environmental sample matrices achieving high selectivity and sensitivity levels. On-line separation and preconcentration of thorium and uranium are carried out by means of UTEVA resin. The potential of the LOV-MSFIA makes possible the full automation of the system by the on-line regeneration of the column. The limits of detection reached are 0.4 ng L -1 of uranium and 2.8 ng L -1 of thorium. The reproducibility of the LOV-MSFIA-ICP-MS is 1.7% of RSD. Moreover, a high sensitivity, a wide working range (0-200 οg L -1 for uranium and thorium) and an injection frequency up to 9 h -1 (depending on the sample volume) should be highlighted. Different water sample matrices (seawater, well water, freshwater, tap water and mineral water), a phosphogypsum sample with natural uranium and thorium content and a channel sediment reference material were satisfactorily analyzed with the proposed method. © 2012 The Royal Society of Chemistry.This work was funded by Spain’s Ministry of Science and Innovation (Project CTQ2010-15541) and Spain’s Ministry of Science and Innovation (Project FIS2008-00781).Peer Reviewe

Flow analysis : a practical guide

x, 278 p.; il.; 23.5 c

Smart thorium and uranium determination exploiting renewable solid-phase extraction applied to environmental samples in a wide concentration range

A smart fully automated system is proposed for determination of thorium and uranium in a wide concentration range, reaching environmental levels. The hyphenation of lab-on-valve (LOV) and multisyringe flow injection analysis (MSFIA), coupled to a long path length liquid waveguide capillary cell, allows the spectrophotometric determination of thorium and uranium in different types of environmental sample matrices achieving high selectivity and sensitivity levels. Online separation and preconcentration of thorium and uranium is carried out by means of Uranium and TEtraValents Actinides resin. The potential of the LOV–MSFIA makes possible the full automation of the system by the in-line regeneration of the column and its combination with a smart methodology is a step forward in automation. After elution, thorium(IV) and uranium(VI) are spectrophotometrically detected after reaction with arsenazo-III. We propose a rapid, inexpensive, and fully automated method to determine thorium(IV) and uranium(VI) in a wide concentration range (0–1,200 and 0–2,000 μg L-1 Th and U, respectively). Limits of detection reached are 5.9 ηg L-1 of uranium and 60 ηg L-1 of thorium. Different water sample matrices (seawater, well water, freshwater, tap water, and mineral water), and a channel sediment reference material which contained thorium and uranium were satisfactorily analyzed with the proposed method.This work was funded by the Spain’s Ministry of Education and Science (Project CTQ2010-15541) and the Spain’s Ministry of Science and Innovation (Project FIS2008-00781). J.A. thanks the Balearic Islands University for funding her research.Peer reviewe

In-syringe magnetic stirring-assisted dispersive liquid-liquid microextraction and silylation prior gas chromatography-mass spectrometry for ultraviolet filters determination in environmental water samples

[eng] A novel online approach involving in-syringe magnetic stirring assisted dispersive liquid-liquid microextraction and derivatization coupled to gas chromatography-mass spectrometry has been developed for the determination of seven UV filters extensively used in cosmetic products in environmental water samples. The effect of parameters such as the type and volume of extraction solvent, dispersive solvent and derivatization agent, pH, ionic strength and stirring time, was studied using multivariate experimental design. Extraction, derivatization and preconcentration were simultaneously performed using acetone as dispersive solvent, N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) as derivatization agent and trichloroethylene as extraction solvent. After stirring during 160 s, the sedimented phase was transferred to a rotary micro-volume injection valve (3 μL) and introduced by an air stream into the injector of the GC through a stainless-steel tube used as interface. The detection limits were in the range of 0.023-0.16 μg L−1 and good linearity was observed up to 500 μg L−1 of the studied UV filters, with R2 ranging between 0.9829 and 0.9963. The inter-day precision expressed as relative standard deviation (n = 5) varied between 5.5 and 16.8%. Finally, the developed method was satisfactorily applied to assess the occurrence of the studied UV filters in seawater and pool water samples. Some of the studied UV filters were found in these samples and an add-recovery test was also successfully performed with recoveries between 82 and 111%

On-line in-syringe magnetic stirring assisted dispersive liquid-liquid microextraction HPLC UV method for UV filters determination using 1-hexyl-3-methylimidazolium hexafluorophosphate as extractant

[eng] An environmental friendly and fully automated method using in-syringe magnetic stirring assisted dispersive liquid-liquid microextraction coupled with high-performance liquid chromatography has been developed for the determination of UV filters in environmental water samples. The main 'green' features on this method are the use of an ionic liquid as extracting solvent, avoiding the use of chlorinated solvents, and the on-line microextraction, preconcentration, separation and detection minimizing the use of reagents and so the waste generation. After sample treatment, 20 µL of the organic droplet was injected onto the HPLC-UV system. Various parameters affecting the extraction efficiency were studied using multivariate optimization approach, including the quantity of extraction and dispersive solvents, extraction and sedimentation time, ionic strength and pH. Under optimized conditions, limits of detection were within the range of 0.08-12 µg/L, for 3.5 mL sample volume. Linearity ranges were up to 500 µg/L for the UV-filters studied. Furthermore, enrichment factors ranging from 11 to 23 folds were obtained. Intra- and inter-assay precisions were 6% and 8%, respectively. Finally, the proposed method was successfully applied to determine UV filters in surface seawater and swimming pool samples attaining satisfactory recoveries over the range of 89-114% and 86-107%, respectively

Analytical strategies for coupling separation and flow-injection techniques

[eng] Flow techniques (FTs) are non-separative tools and high-performance separation techniques that require sample pretreatment. On-line combinations of flow sample-pretreatment units and discrete sampleintroduction devices are very attractive, as they allow the whole analytical sequence to be developed in a single instrumental assembly. In this review, we present the state of the art and future trends in coupling separation techniques, such as chromatography and capillary electrophoresis, and FTs. FTs can be coupled as a front end to separation techniques or by integrating the separation column in the flow system, generating new low-pressure chromatographic techniques.We discuss different coupling strategies, highlighting their benefits and disadvantages.We also present an updated review of coupled systems applied to environmental and biological sample

Parabenos determination in cosmetic and personal care products Exploiting a Multi-Syringe Chromatographic (MSC) system and chemiluminescent detection

[eng] Parabensarewidelyusedindairyproducts,suchasincosmeticsandpersonalcareproducts.Thus,inthis workamulti-syringechromatographic(MSC)systemisproposedforthe first timeforthedetermination of fourparabens:methylparaben(MP),ethylparaben(EP),propylparaben(PP)andbutylparaben(BP)in cosmetics andpersonalcareproducts,asasimpler,practical,andlowcostalternativetoHPLCmethods. Separation wasachievedusinga5mm-longprecolumnofreversedphaseC18andmulti-isocratic separation, i.e.usingtwoconsecutivemobilephases,12:88acetonitrile:waterand28:72acetonitrile: water.Theuseofamulti-syringeburetallowedtheeasyimplementationofchemiluminescent(CL) detection afterseparation.ThechemiluminescentdetectionisbasedonthereductionofCe(IV)by p-hydroxybenzoicacid,productoftheacidhydrolysisofparabens,toexciterhodamine6G(Rho6G)and measure theresultinglightemission.Multivariatedesignscombinedwiththeconceptsofmultiple response treatmentsanddesirabilityfunctionshavebeenemployedtosimultaneouslyoptimizeand evaluatetheresponses.Theoptimizedmethodhasprovedtobesensitiveandprecise,obtaininglimitsof detection between20and40 mg L 1 and RSD o4.9% inallcases.Themethodwassatisfactorilyapplied to cosmeticsandpersonalcareproducts,obtainingnosignificant differencesataconfidence levelof95% comparing withtheHPLCreferencemethod