Showing papers on "Fluorescence spectrometry published in 2014"

Atomic spectrometry update – a review of advances in environmental analysis

Abstract: This is the 30th annual review of the application of atomic spectrometry to the chemical analysis of environmental samples. This Update refers to papers published approximately between August 2013 and July 2014 and continues the series of Atomic Spectrometry Updates (ASUs) in environmental analysis that should be read in conjunction with other related ASUs in the series, namely: clinical and biological materials, foods and beverages, advances in atomic spectrometry and related techniques, elemental speciation,X-ray fluorescence spectrometry, and the analysis of metals, chemicals and functional materials. In the field of air analysis, highlights within this review period included: the use of 3D printing technology for the rapid prototyping of new air sampler components; single particle ICP-MS studies; use of a new triple-quadrupole ICP-MS for the analysis of radioactive species and the use of FEG-SEM and IBA for the analysis of gun-shot residues. In the field of water analysis, methods continue to be developed: for the extraction and preconcentration of elements; speciation of As, Cr, Hg and Sb forms and determination of elemental constituents in colloidal and NP fractions. Instrumental developments reported include the use of MC-ICP-MS for isotopic tracer studies and a review of XRF techniques and associated preconcentration procedures for trace element analysis. Many articles featuring the analysis of plants and soils appeared but, as usual, most focused on environmental applications rather than the advancement of atomic spectrometry. There have, however, been interesting developments, such as the almost bewildering increase in types of micro-extraction for analyte preconcentration and the resurgence of CS-AAS. Clearly LIBS is maturing rapidly, with soil analysis becoming more routine in nature. Also notable was the way the accident at the Fukishima-Daiichi nuclear power plant triggered development of analytical methods for the assessment of contamination in the surrounding area. Recent research indicates that geological applications still drives many of the instrumental and methodological advances in LA-ICP-MS. Fundamental studies continue to shed light on the processes involved and hence ways of improving the analysis of laser-produced aerosols. The preparation of NP powders for the production of matrix-matched RMs for microanalytical techniques such as LA-ICP-MS and SIMS showed great promise for addressing one of the major issues when analysing geological materials by these techniques. Steady advances in MC-ICP-MS methodology is feeding through to applications in isotope geochemistry, while new SIMS instrumentation is being directed towards probing fine growth structures in biogenic carbonates and inferring past climate conditions from their geochemistry. Feedback on this review is most welcome and the review coordinator can be contacted using the email address provided.

A mitochondrion-targeting copper complex exhibits potent cytotoxicity against cisplatin-resistant tumor cells through multiple mechanisms of action

Abstract: Copper complexes are potential anticancer drugs by virtue of their available redox properties and low toxicity. In this study, a copper(II) complex, [Cu(ttpy-tpp)Br2]Br (simplified as CTB, ttpy-tpp = 4′-p-tolyl-(2,2′:6′,2′′-terpyridyl)triphenylphosphonium bromide), is synthesized and characterized by X-ray crystallography and ESI-MS as a targeted anticancer agent. Triphenylphosphine (TPP) is introduced into the complex for its mitochondrion-targeting ability and lipophilic character. The uptake of CTB by tumor cells and mitochondria was determined by ICP-MS or fluorescence spectrometry. CTB is able to cross the cytoplasmic and mitochondrial membranes of tumor cells and influence the mitochondrial membrane potential more profoundly than the anticancer drug cisplatin. The cytotoxicity of CTB was tested on MCF-7, HeLa, Skov-3, A549 and cisplatin-resistant A549R tumor cells by MTT assay. CTB is more cytotoxic against these cells than cisplatin; particularly, it is highly effective against cisplatin-resistant tumor cells. The interaction between CTB and DNA has been studied by spectroscopic methods and agarose gel electrophoresis. CTB strongly interacts with DNA via intercalation stabilized by electrostatic forces, and displays a significant cleavage activity towards supercoiled pBR322 DNA and cellular DNA through an oxidative mechanism. The cytotoxicity of CTB seems to result from multiple mechanisms of action, including the modification of DNA conformation, generation of reactive oxygen species, scission of DNA strands, and dissipation of mitochondrial membrane potential. The delocalized cationic property and high hydrophilicity of CTB favours its selective accumulation in cancer cells and mitochondria. This study demonstrates that copper complexes with mitochondrion-targeting function could be efficient anticancer drugs immune to the drug resistance of cisplatin.

Trace and ultratrace analysis of liquid samples by X-ray fluorescence spectrometry

Abstract: This article gives an overview of the state-of-the-art of recent preconcentration strategies published in X-ray fluorescence spectrometry (XRF), including the use of microextraction procedures, nanomaterials, filters and activated thin layers. We give special attention to current XRF instrumentation and the advantages and the limitations of each mode (including large-scale instrumentation, bench-top spectrometers and hand-held systems). Also, we comment on and discuss trends and future perspectives of XRF spectrometry in trace and ultratrace analysis of liquid samples.

Preparation and Mechanism Insight of Nuclear Envelope-like Polymer Vesicles for Facile Loading of Biomacromolecules and Enhanced Biocatalytic Activity

Abstract: The facile loading of sensitive and fragile biomacromolecules, such as glucose oxidase, hemoglobin, and ribonucleic acid (RNA), via synthetic vehicles directly in pure aqueous media is an important technical challenge. Inspired by the nucleus pore complex that connects the cell nucleus and the cytoplasm across the nuclear envelope, here we describe the development of a kind of polymeric nuclear envelope-like vesicle (NEV) to address this problem. The NEV is tailored to form the polymer pore complex (70 nm, similar to a nucleus pore complex) within the vesicle membrane based on nanophase segregation, which is confirmed via fluorescence spectrometry and dynamic light scattering (DLS) during self-assembly. This pH-triggered polymer pore complex can mediate the transportation of biomacromolecules across the vesicle membrane. Moreover, the NEVs facilitate the natural consecutive enzyme-catalyzed reactions via the H+ sponge effect. This simple strategy might also be extended for mimicking other synthetic cell o...

Metals analysis of agricultural soils via portable X-ray fluorescence spectrometry.

Abstract: To assess the applicability of portable X-ray fluorescence (PXRF) spectrometry for metals analysis, total concentrations of As, Pb, Cu, and Zn in 47 agricultural soils were determined using in situ PXRF analysis, ex situ PXRF analysis, and conventional laboratory analysis The correlation regression parameters of PXRF data with the data of conventional analysis were significantly improved upon going from in situ to ex situ, indicating that improvement of the ex situ PXRF data quality was achieved thorough sample preparation Use of PXRF in situ was inferior to other analyses, especially when attempting to quantify relatively low levels of metals in agricultural soils A high degree of linearity and similar spatial distribution existed between ex situ PXRF and laboratory analysis, suggesting that PXRF can be used in rapid detection or screening of agricultural soils, but is best followed with additional sample preparation ex situ and laboratory confirmation

A Simple and Sensitive Approach for Ochratoxin A Detection Using a Label-Free Fluorescent Aptasensor

Abstract: Ochratoxin A(OTA) is found to be one of the predominant contaminating mycotoxins in a wide variety of food commodities. To avoid the risk of OTA consumption, the detection and quantitation of OTA level are of great significance. Based on the fact that ssDNA aptamer has the ability to form a double-strand structure with its complementary sequence, a simple and rapid aptamer-based label-free approach for highly sensitive and selective fluorescence detection of OTA was developed by using ultra-sensitive double-strand DNA specific dyes PicoGreen. The results showed that as low as 1 ng/mL of OTA could be detected with a dynamic range of more than 5 orders of magnitude which satisfies the requirements for OTA maximum residue limit in various food regulated by European Commission. With the specificity of aptamer, the assay exhibited high selectivity for OTA against two other analogues (N-acetyl-l-phenylalanine and zearalenone). We also tested the aptasensor practicability using real sample of 1% beer spiked with a series of concentration of OTA and the results show good tolerance to matrix effect. All detections could be achieved in less than 30 min, which provides a simple, quick and sensitive detection method for OTA screening in food safety and could be easily extend to other small molecular chemical compounds detection which aptamer has been selected.

Heavy metal contamination in dust from kindergartens and elementary schools in Xi’an, China

Abstract: Concentrations of As, Ba, Co, Cr, Cu, Mn, Ni, Pb, V, and Zn in campus dust from kindergartens and elementary schools in Xi’an, China, were analyzed using X-ray fluorescence spectrometry and heavy metal contamination levels were assessed based on the geoaccumulation index (I geo), enrichment factor (EF) and numero synthesis pollution index (NSPI). The results indicate that, in comparison with Shaanxi soil, dust samples have elevated metal concentrations as a whole, except for V, Mn, Ni, and As. The assessment results of I geo and EF indicate that V, Mn, Ni, and As in campus dust are uncontaminated, while Ba and Cr are uncontaminated to moderately contaminated, and Co, Cu, Pb, and Zn are moderately to strongly contaminated. The NSPI results show that most dust samples presented heavily contaminated by heavy metals. More attention should be paid to heavy metal contamination of campus dust from kindergartens and elementary schools of Xi’an.

Separation, detection and characterisation of engineered nanoparticles in natural waters using hydrodynamic chromatography and multi-method detection (light scattering, analytical ultracentrifugation and single particle ICP-MS)

Abstract: Environmental context The effects of engineered nanoparticles on the environment and on human health are difficult to evaluate largely because nanoparticles are so difficult to measure. The main problems are that concentrations are low and the engineered nanoparticles are often difficult to distinguish from the environmental matrices in which they are found. We report a separation technique that facilitates the detection of engineered nanoparticles in natural waters. Abstract Few analytical techniques are presently able to detect and quantify engineered nanoparticles (ENPs) in the environment. The major challenges result from the complex matrices of environmental samples and the low concentrations at which the ENPs are expected to be found. Separation techniques such as asymmetric flow field flow fractionation (AF4) and more recently, hydrodynamic chromatography (HDC) have been used to partly resolve ENPs from their complex environmental matrices. In this paper, HDC was first coupled to light scattering detectors in order to develop a method that would allow the separation and detection of ENPs spiked into a natural water. Size fractionated samples were characterised using off-line detectors including analytical ultracentrifugation (AUC), dynamic light scattering (DLS) and single particle inductively coupled plasma mass spectrometry (SP-ICP-MS). HDC was able to separate a complex mixture of polystyrene, silver and gold nanoparticles (radii of 60, 40, 20 and 10nm) contained within a river water matrix. Furthermore, the feasibility of using HDC coupled to SP-ICP-MS was demonstrated by detecting 4µgL–1 of a 20-nm (radius) nAg in a river water sample.

Metal-organic framework-based molecular beacons for multiplexed DNA detection by synchronous fluorescence analysis.

Abstract: We report a new sensor combined two dimensional metal–organic framework (MOF), N,N-bis(2-hydroxy-ethyl)dithiooxamidato copper(II) (H2dtoaCu), with the hairpin-structured oligonucleotides and demonstrate its feasibility in detecting multiplexed sequence-specific DNA. The key component of this sensor (MOF–MBs) is the hairpin-structured fluorescent oligonucleotide that allows the MOFs to function as both a “nanoscaffold” for the oligonucleotide and a “nanoquencher” of the fluorophore. An oligonucleotide sequence fragment of wild-type HBV (T1) and a reverse-transcription oligonucleotide sequence of RNA fragment of HIV (T2) were used as model systems. While in the presence of the targets, the fluorescence of dyes was recovered by forming a double strand structure. Multiplex DNA detection can be realized by synchronous scanning fluorescence spectrometry, and there was no cross reaction between the two probes. Under the optimum conditions, the fluorescence intensities of two dyes all exhibit good linear dependence on their target DNA concentration in the range of 1–10 nM with the detection limit of 0.87 nM and 0.22 nM for T1 and T2, respectively. As a proof of concept, the MOF–MBs have been successfully used as a potential sensing platform for simultaneous detection of multiplexed DNA.

Forty Thousand Arms for a Single Emperor: From Chemical Data to the Labor Organization Behind the Bronze Arrows of the Terracotta Army

Abstract: This paper explores the integration of chemical data with metric studies and spatial analyses of archaeological artifacts to investigate questions of specialization, standardization, and production organization behind large-scale technological enterprises. The main analytical focus is placed on the 40,000 bronze arrowheads recovered with the Terracotta Army in the First Emperor’s Mausoleum, Xi’an, China. Based on the identification by portable X-ray fluorescence spectrometry of chemical clusters that correspond to individual metal batches, and combined with a study of their context in the tomb complex, we argue that the manufacture of arrows was organized via a cellular production model with various multi-skilled units rather than as a single production line. This system favored more adaptable and efficient logistical organization that facilitated dynamic cross-craft interaction while maintaining remarkable degrees of standardization. We discuss the use of “the batch” as an analytical category and how our method might be applied to other studies of craft organization in complex societies and imperial systems.

Speciation mapping of environmental samples using XANES imaging

Abstract: Environmental context Recently developed fast fluorescence detectors have opened the way to the development of element speciation mapping, i.e. X-ray absorption near edge spectroscopy (XANES) imaging, of environmental samples. This technique is potentially very informative but is also highly data intensive. Here, we used XANES imaging to explore the distribution of Cu species in biosolid materials, destined for agricultural use, as this is of importance in relation to the bioavailability and potential toxicity of this metal. Abstract Fast X-ray detectors with large solid angles and high dynamic ranges open the door to XANES imaging, in which millions of spectra are collected to image the speciation of metals at micrometre resolution, over areas up to several square centimetres. This paper explores how such multispectral datasets can be analysed in order to provide further insights into the distribution of Cu species in fresh and stockpiled biosolids. The approach demonstrated uses Principal Components Analysis to extract the ‘significant’ spectral information from the XANES maps, followed by cluster analysis to locate regions of contrasting spectral signatures. Following this model-free analysis, pixel-by-pixel linear combination fits are used to provide a direct link between bulk and imaging XANES spectroscopy. The results indicate that both the speciation and distribution of Cu species are significantly affected by ageing. The majority of heterogeneously distributed micrometre-sized Cu sulfide particles present in fresh biosolids disappear during the oxidative stockpiling process. In aged biosolids most of the Cu is homogeneously redistributed on organic matter suggesting that Cu mobility is temporarily increased during this redistribution process. This manuscript demonstrates how large XANES imaging datasets could be analysed and used to gain a deep understanding of metal speciation in environmental samples.

Two polypyridyl copper(II) complexes: synthesis, crystal structure and interaction with DNA and serum protein in vitro

Abstract: Two polypyridyl copper(II) complexes, [Cu(acac)(p-CPIP)(CH3OH)](NO3) (1) and [Cu(acac)(o-NPIP)(NO3)] (2) (acac = acetylacetonate, p-CPIP = 2-(4-chlorophenyl)imidazo[4,5-f]1,10-phenanthroline, o-NPIP = 2-(2-nitrophenyl)imidazo[4,5-f]1,10-phenanthroline), have been synthesized and characterized by single-crystal analysis, IR and electronic spectroscopy. X-ray analyses reveal that both 1 and 2 possess a triclinic crystal system with Pmn1 and mononuclear five-coordinated square pyramidal geometry, which were further linked to a one-dimensional structure through π–π stacking and intermolecular hydrogen bonds. The interaction of the Cu(II) complex with calf thymus DNA (CT-DNA) was investigated by UV-visible and fluorescence emission spectrometry, as well as agarose gel electrophoresis. The apparent binding constant (Kapp) values of 2.47 × 104 M−1 for 1 and 3.04 × 104 M−1 for 2 suggest moderate intercalative binding mode between the complexes and DNA. Both complexes displayed efficient oxidative cleavage of supercoiled DNA in the presence of external agents. In addition, fluorescence spectrometry of bovine serum albumin (BSA) with the complexes showed that the quenching mechanism of 1 might be a dynamic procedure, while 2 showed a combined dynamic and static quenching mechanism. For both 1 and 2, the number of binding sites was about one for BSA. Moreover, synchronous fluorescence spectral experiments revealed that 1 and 2 affect the microenvironment of tryptophan residues of BSA.

Design and construction of a multiwavelength, micromirror total internal reflectance fluorescence microscope

Abstract: Colocalization single-molecule spectroscopy (CoSMoS) enables multiple molecules to be simultaneously monitored. This protocol describes how to construct a CoSMoS micromirror total internal reflection fluorescence microscope.

Dynamics and hydration explain failed functional transformation in dehalogenase design

Abstract: We emphasize the importance of dynamics and hydration for enzymatic catalysis and protein design by transplanting the active site from a haloalkane dehalogenase with high enantioselectivity to nonselective dehalogenase. Protein crystallography confirms that the active site geometry of the redesigned dehalogenase matches that of the target, but its enantioselectivity remains low. Time-dependent fluorescence shifts and computer simulations revealed that dynamics and hydration at the tunnel mouth differ substantially between the redesigned and target dehalogenase.

Geological Applications of Laser-Induced Breakdown Spectroscopy

Abstract: Laser-induced breakdown spectroscopy (LIBS) records light emitted from the decay of electrons to lower-energy orbitals during cooling of laser-induced ablation plasmas; the resultant spectra can be used in a variety of geoanalytical applications. Four aspects of LIBS analysis distinguish LIBS from traditional laboratory-based analytical techniques: (i) the lack of necessary sample preparation, allowing rapid analysis of many samples, (ii) the ability to analyse both 20 to 100 μm-diameter spots and whole rocks, (iii) the detailed chemical signature contained in a LIBS spectrum and (iv) the ability to take LIBS into the field in backpack portable instrumentation. Three case studies illustrate potential applications of LIBS in the geosciences. First, analysis of the Carrizozo basalt flow in New Mexico, USA, illustrated that LIBS spectra could discriminate between samples of similar composition within uncertainties typical of whole-rock analysis by X-ray fluorescence spectrometry. Second, spectra from four sets of rubies from Madagascar and Tanzania illustrate the use of LIBS and multivariate analysis to determine provenance with success rates of > 95%. This technique can also be applied to correlation of units. Finally, a chemical map of a copper ore from Butte, MT, USA, illustrates the use of spatially defined LIBS spectra to understand chemical variations within textural context. La spectroscopie sur plasma induit par laser (LIBS) enregistre la lumiere emise par le passage d’electrons a des orbitales de plus basse energie lors du refroidissement de plasmas induits par une ablation laser; les spectres resultant peuvent etre utilise pour une variete d'applications geochimiques. Quatre aspects de l'analyse LIBS la distinguent des techniques d'analyses traditionnelles de laboratoire: (1) la non necessite de preparer les echantillons, permettant une analyse rapide de nombreux echantillons, (2) la capacite d'analyser aussi bien des zones de 20 a 100 μm que des roches totales, (3) la signature chimique detaillee contenue dans un spectre LIBS et (4) la possibilite d'emporter le LIBS sur le terrain sous forme d'un instrument transportable dans un sac a dos. Trois etudes de cas illustrent les applications potentielles du LIBS dans les geosciences. Premierement, l'analyse de la coulee de basalte de Carrizozo au Nouveau-Mexique, Etats-Unis demontre que les spectres LIBS peuvent distinguer des echantillons de composition similaire dans lesniveaux d'incertitudes typiques de l'analyse des roches totales par spectrometrie de fluorescence X. Deuxiemement, les spectres de quatre series de rubis de Madagascar et de Tanzanie illustrent l'utilisation du LIBS et d'une analyse multivariee pour determiner la provenance a des taux de reussite > 95%. Cette technique peut egalement etre appliquee pour la correlation d'unite. Enfin, une carte chimique d'un minerai de cuivre de Butte, MT, Etats-Unis, illustre l'utilisation des spectres LIBS spatialement definis pour comprendre les variations chimiques dans un contexte textural.

Observations and assessment of iron oxide and green rust nanoparticles in metal-polluted mine drainage within a steep redox gradient

Abstract: Environmental context Legacy contamination from mining operations is a serious and complex environmental problem. We examine a former uranium mine where groundwater leaving the site enters a stream with chemically dramatic effects resulting in a fundamental change in the way contaminant metals are transported to the surface environment. The results are important for our understanding of how these contaminants are dispersed, and how they could interact with the biosphere. Abstract In this study of iron- and silica-bearing nanoparticle and colloid aggregates in slightly acidic mine drainage, we combined bulk scale geochemistry techniques with detailed nanoscale analyses using high-resolution transmission electron microscopy (HR-TEM) to demonstrate the complexity of iron oxide formation and transformation at a steep redox gradient (groundwater outflow into a stream), and the resulting role in metal(loid) uptake. We also identified pseudohexagonal nanosheets of Zn-bearing green rust in outflowing groundwater using HR-TEM. This is only the second study where green rust was identified in groundwater, and the second to examine naturally occurring green rust with analytical TEM. In aerated downstream waters, we found aggregates of poorly crystalline iron oxide particles (20–200nm in diameter). Inductively coupled plasma–mass spectrometry (ICP-MS) analysis of water fractions shows that most elements such as Ni and Zn were found almost exclusively in the dissolved–nanoparticulate (<0.1μm) fraction, whereas Cu and As were primarily associated with suspended particles. In the underlying sediments composed of deposited particles, goethite nanoneedles formed on the ferrihydrite surfaces of larger aggregated particles (100–1000nm), resulting in more reactive surface area for metal(loid) uptake. Sequential extraction of sediments showed that many metal(loid)s, particularly As and Zn, were associated with iron oxides identified as ferrihydrite, goethite and possibly schwertmannite. Amorphous silica co-precipitation with iron oxides was prevalent at all sampling sites, but its effect on metal(loid) sorption is unknown. Fine-grained iron oxide sediments are easily remobilised during turbulent flow events, adding to the mobility of the associated metals.

Recyclable Decoration of Amine-Functionalized Magnetic Nanoparticles with Ni2+ for Determination of Histidine by Photochemical Vapor Generation Atomic Spectrometry

Abstract: It is critically important to accurately determine histidine since it is an indicator for many diseases when at an abnormal level. Here, an inexpensive and simple method using an amine-functionalized magnetic nanoparticle-based Ni2+–histidine affinity pair system was developed for highly sensitive and selective detection of histidine in human urine by photochemical vapor generation atomic spectrometry. Ni2+ was first bound to the amine groups of the amine-functionalized magnetic nanoparticles and then liberated to solution via the highly specific interaction between the histidine and Ni2+ in the presence of histidine. The liberated histidine–Ni2+ complex was exposed to UV irradiation in the presence of formic acid to form gaseous nickel tetracarbonyl, which was separated from the sample matrix and determined by atomic absorption/fluorescence spectrometry. Compared to other methods, this approach promises high sensitivity, simplicity in design, and convenient operation. The need for organic solvents, enzym...

Hyperspectral imaging, spectrofluorimetry, FORS and XRF for the non-invasive study of medieval miniatures materials

Abstract: Illuminated manuscripts are complex multi-layer and multi-material objects. To this difficulty, from the analytical point of view, is added the impossibility of removing samples from these paintings for the study of their materials and techniques. There are relatively few analytical methods that satisfy these constraints as the availability of non-invasive techniques adapted to painted manuscripts is limited and mainly focused on the characterization of inorganic compounds. In the context of a research project on the analytical study of the forty miniatures in the Marcade collection (Treasury of the Saint-Andre Cathedral of Bordeaux, XIII to XVI century), the potential of two non-invasive methods, hyperspectral imaging (HSI) and spectrofluorimetry is explored. The methodological development of these techniques as well as preliminary tests on miniatures recreated according to medieval recipes and materials, allowed the validation of the analytical parameters and the creation of a database of reference spectra (parchments, pigments, binders). Hyperspectral imaging associates reflectance spectra with each pixel of the image and treats the signal received in various wavelengths. The characteristics of the spectral signal in VIS range or NIR are used to get an identification and a localization of the components. It allows the study of the entire image and offers lots of ways to work: comparison of spectra, mapping, principal component analyses and false color images. Spectrofluorimetry is a sensitive method which gives information on fluorescent organic compounds under UV or visible light. Emission and excitation spectra of five red pigments in binding media have been collected. These methods were compared with X-ray fluorescence spectrometry for the qualitative analysis and mapping of the inorganic elements in a facsimile which had been purposely reproduced by an illumination painter who worked with original medieval recipes for the sake of developing the present study. The combination of all these techniques allows good identification of all the materials used on an illuminated manuscript. The pertinent selection of the wavelengths used with the HSI system and a preliminary database and study of materials under UV and white light is described in this paper.

Adsorption and photocatalytic decomposition of roxarsone by TiO2 and its mechanism

Abstract: Roxarsone (3-nitro-4-hydroxyphenylarsonic acid) has been widely used as organic arsenic additive in animal industry. In this study, the adsorption of roxarsone on TiO₂ under dark conditions, the photocatalytic decomposition of roxarsone under UV/TiO₂, and the possible photocatalytic pathway were investigated. At the initial concentration of 5-35 mg/L, the adsorption of roxarsone fitted well with the pseudo-second-order kinetics. The isotherms analysis showed that the Langmuir model was better than the Freundlich and Dubinin–Radushkevich models for describing the adsorption process. After 7 h of photocatalytic decomposition, a complete disappearance of roxarsone was achieved. The pH value has a significant effect on both adsorption and photocatalytic decomposition of roxarsone. The results of high-performance liquid chromatography-hydride generation-atomic fluorescence spectrometry (HPLC-HG-AFS) and gas chromatography-mass spectrometry (GC/MS) analyses proved the cleavage of the As-C bond during the photocatalytic decomposition process by TiO2 and the intermediates of the decomposition. Based on the results, a possible photocatalytic decomposition pathway was proposed.

Photolysis and TiO2-catalysed degradation of diclofenac in surface and drinking water using circulating batch photoreactors

Abstract: The occurrence of diclofenac (DCF) as an emerging pollutant in surface waters and drinking water has been attributed to elevated global consumption and the inability of sewage treatment plants to remove DCF. In this study, DCF spikeddrinkingwaterandriver waterwassubjectedtophotolysisandTiO2photocatalytictreatmentsinacirculating laboratory-scale(immersion-well)andademonstration-scaleloopreactor(Laboclean).Theoperationalparametersforthe immersion-well reactor were optimised as follows: TiO2 P25 loading, 0.1gL � 1 ; natural pH, 6.2; initial concentration, 30mgL � 1 ; water type, distilled water. Complete DCF removal was realised within 15min under the optimised conditions using the immersion-well reactor. Sunlight-mediated photochemical degradation required aprolonged exposure period of up to 360min for complete DCF removal. DCF in distilled and drinking water was efficiently degraded in the larger Laboclean reactor. Differences were, however, observed based on their pseudo-first-order rate constants, which implies that the water matrix has an effect on the degradation rate. Six major photoproducts, 2-(8-chloro-9H-carbazol-1-yl)acetic acid, 2-(8-hydroxy-9H-carbazol-1-yl)acetic acid, 2,6-dichloro-N-o-tolylbenzenamine, 2-(phenylamino)benzaldehyde, 1-chloromethyl-9H-carbazole and 1-methyl-9H-carbazole, generated from TiO2 photocatalysis of DCF were identified by liquid chromatography-mass spectrometry (LCMS) and Fourier transform-ion cyclotron resonance-mass spectro- metry (FT-ICR-MS). This work has shown that photocatalytic degradation kinetics of DCF are dependent on both the geometry of the photoreactor and the nature of the water matrices. Additional keywords: advanced oxidation processes, pharmaceuticals, photocatalysis, titanium dioxide.