A study of arsenic speciation in soil, irrigation water and plant tissue: A case study of the broad bean plant, Vicia faba.

Samples of soil, the broad bean plant, Vicia faba and irrigation water were collected from the same agricultural site in Dokan, in the Kurdistan region of Iraq. Total arsenic and arsenic speciation were determined in all materials by ICP-MS and HPLC-ICP-MS, respectively. Available arsenic (11%) was also determined within the soil, together with Cd, Cr, Cu, Ni, Zn, Fe and Mn. The concentrations of total arsenic were: soil (5.32µgg(-1)), irrigation water (1.06µgL(-1)), roots (2.065µgg(-1)) and bean (0.133µgg(-1)). Stems, leaves and pods were also measured. Inorganic As(V) dominated soil (90%) and root (78%) samples. However, organo-arsenic (MMA, 48% and DMA, 19%) was the more dominant species in the edible bean. The study provides an insight into the uptake, preferred disposal route, speciation changes and loss mechanism involved for arsenic with this food source.

An evaluation of extraction techniques for arsenic in staple diets (fish and rice) utilising both classical and enzymatic extraction methods.

Enzymatic extraction methods were evaluated with classical extraction approaches for the determination of arsenic in food. The extraction efficiency for total arsenic was determined by analysing CRM materials DORM-3 fish protein, NIES 106 rice flour and GBW10015 spinach. These were compared with total arsenic concentration determined using microwave-assisted acid digestion and ICP-MS. The total arsenic concentrations in the CRM materials were in good agreement with the certified values. Enzymatic hydrolysis using trypsin has been successfully employed to extract arsenic species in DORM-3 and fish samples. Whilst this method of hydrolysing the proteins worked well for the fish samples, an alternative approach was required to facilitate the digestion of cellulose in plant materials. However, enzymatic extraction using cellulase was found to give unsatisfactory results for both the NIES and GBW10015 CRM materials. Dilute nitric acid (1% HNO3) was found to give a more efficient extraction for arsenic species in the same CRM materials and rice samples. The study was extended to evaluate a range of real samples. Total arsenic concentrations in 13 different types of fish tissue were determined following microwave-assisted acid digestion using nitric acid/hydrogen peroxide, followed by measurement using HPLC-ICP-MS for speciation analysis. The results obtained for fish were in the range of 3.53-98.80 µg g(-1) As (dry weight). Similarly, the results of 17 rice samples were in the range of 0.054-0.823 µg g(-1). This study demonstrates the importance of selecting an appropriate extraction technique for the quantitative measurement of arsenic species in food.

A novel ligandless-dispersive liquid-liquid microextraction method for matrix elimination and the preconcentration of rare earth elements from natural waters.

A new, simple, efficient and rapid separation method based on ligandless-dispersive liquid-liquid microextraction (LL-DLLME) was developed for the preconcentration of rare earth elements (REEs) (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) in natural water samples, followed by inductively coupled plasma mass spectrometry (ICP-MS) detection. Carbon tetrachloride and acetone were used as extraction solvent and disperser solvent, respectively. The experimental parameters affecting the extraction efficiency such as sample pH, volume of extraction/disperser solvent and concentration of NaCl were investigated and optimized. Under the optimum conditions, detection limits between 0.68 and 26.6 ng L(-1) for a 5 mL sample volume were determined. The developed method was successfully applied to samples such as tap water, river water and seawater. Satisfactory recoveries were obtained with the percentage recovery values of the REEs for spiked water samples being between 94 and 111 for tap water, between 89 and 118 for river water and between 92 and 124 for seawater.

Artificial soils from alluvial tin mining wastes in Malaysia--a study of soil chemistry following experimental treatments and the impact of mycorrhizal treatment on growth and foliar chemistry.

For decades Malaysia was the world's largest producer of Sn, but now the vast open cast mining operations have left a legacy of some 100,000 ha of what is effectively wasteland, covered with a mosaic of tailings and lagoons. Few plants naturally recolonise these areas. The demand for such land for both urban expansion and agricultural use has presented an urgent need for better characterisation. This study reports on the formation of artificial soils from alluvial Sn mining waste with a focus on the effects of experimental treatments on soil chemistry. Soil organic matter, clay, and pH were manipulated in a controlled environment. Adding both clay tailings and peat enhanced the cation exchange capacity of sand tailings but also reduced the pH. The addition of peat reduced the extractable levels of some elements but increased the availability of Ca and Mg, thus proving beneficial. The use of clay tailings increased the levels of macro and micronutrients but also released Al, As, La, Pb and U. Additionally, the effects of soil mix and mycorrhizal treatments on growth and foliar chemistry were studied. Two plant species were selected: Panicum milicaeum and Pueraria phaseoloides. Different growth patterns were observed with respect to the additions of peat and clay. The results for mycorrhizal treatment (live inoculum or sterile carrier medium) are more complex, but both resulted in improved growth. The use of mycorrhizal fungi could greatly enhance rehabilitation efforts on sand tailings.

Determination of gallium at trace levels using a spectrofluorimetric method in synthetic U-Ga and Ga-As solutions.

A simple, easy to use and selective spectrofluorimetric method for the determination of trace levels of gallium has been developed. A new Schiff base, N-o-vanillidine-2-amino-p-cresol (OVAC) was synthesized and its fluorescence activity with gallium investigated. Based on this chelation reaction, a spectrofluorimetric method has been developed for the determination of gallium in synthetically prepared Ga-U and Ga-As samples buffered at pH 4.0 using acetic acid-sodium acetate. The chelation reaction between Ga(III) and N-o-vanillidine-2-amino-p-cresol was very fast, requiring only 30min at room temperature to complex completely. The limit of detection (LOD) (3sigma) for Ga(III) was 7.17 nM (0.50 microgL(-1)), determined from the analysis of 11 different solutions of 20 microg L(-1) Ga(III).

Determination of trace heavy metals in soil and sediments by atomic spectrometry following preconcentration with Schiff bases on Amberlite XAD-4.

A matrix separation and analyte preconcentration system using Amberlite XAD copolymer resins functionalized by Schiff base reactions coupled with atomic spectrometry has been developed. Three different functionalized Amberlite XAD resins were synthesized using 4-phenylthiosemicarbazide, 2,3-dihydroxybenzaldehyde and 2-thiophenecarboxaldehyde as reagents. These resins could be used to preconcentrate transition and other trace heavy metal analytes from nitric acid digests of soil and sediment samples. Analyte retention was shown to work well at pH 6.0. After treatment of the digests with sodium fluoride and buffering to pH 6, samples that contain extremely large concentrations of iron were analysed for trace analytes without the excess iron overloading the capacity of the resin. The analytes Cd, Co, Cu, Ni and Pb were preconcentrated from acid extracts of certified soil/sediment samples and then eluted with 0.1M HNO(3) directly to the detection system. Flame atomic absorption spectrometry was used as a means of detection during the studies. The efficiency of the chelating resin and the accuracy of the proposed method were evaluated by the analysis of soil (SO-2) and sediment (LGC 6157 and MESS-3) certified reference materials.

Flow injection determination of aluminium by spectrofluorimetric detection after complexation with N-o-vanillidine-2-amino-p-cresol: the application to natural waters.

An on-line flow injection spectrofluorimetric method for the direct determination of aluminium in water samples is described. The method is based on the reaction of aluminium with N-o-vanillidine-2-amino-p-cresol (OVAC) in acidic medium at pH 4.0 to form a water-soluble complex. The excitation and emission wavelengths were 423.0 and 553.0nm, respectively, at which the OVAC-Al complex gave the maximum fluorescence intensity at pH 4.0 in a 50% methanol-50% water medium at 50 degrees C. An interference from fluoride ions was minimised by the addition of Be(2+). Other ions were found not to interfere at the concentrations likely to be found in natural waters. The proposed methods were validated in terms of linearity, repeatability, detection limit, accuracy and selectivity. Under these conditions, the calibration was linear up to 1000microgL(-1) (r=0.999). The limit of detection (3sigma) for the determination of Al(III) was 0.057microgL(-1) and the precision for multiple determinations of 3ngmL(-1) Al(III) prepared in ultra-pure water was found to be 0.62% (n=10). The Schiff base ligand could be used to determine ultra-trace aluminium from natural waters. Analysis of environmental certified reference materials showed good agreement with the certified values. The procedure was found to be equally applicable to both freshwater and saline solutions, including seawater.

The sensitive and selective determination of aluminium by spectrofluorimetric detection after complexation with N-o-vanillidine-2-amino-p-cresol.

A simple, easy to use and selective spectrofluorimetric method for the determination of trace levels of aluminium has been developed. A new Schiff base, N-o-vanillidine-2-amino-p-cresol (OVAC), has been synthesized and its fluorescence activity with aluminium investigated. Based on this chelation reaction, a spectrofluorimetric method has been developed for the determination of aluminium in samples buffered at pH 4.0 using acetic acid-sodium acetate. The chelation reaction between Al(iii) and N-o-vanillidine-2-amino-p-cresol was very fast, requiring only 20 min at room temperature to complex completely. The excitation and emission wavelengths were 423.0 and 553.0 nm, respectively, at which the OVAC-Al complex gave the maximum fluorescence intensity at pH 4.0 in a 50% ethanol-50% water medium. The interference from fluoride ions was minimized by the addition of Be(2+). Other ions were found not to interfere at the concentrations likely to be found in natural waters. Under these conditions, the calibration plot was linear up to 1000 microg L(-1) (r = 0.999). The limit of detection (3sigma) for the determination of Al(iii) was 0.19 microg L(-1) and the precision for multiple determinations of 3 ng mL(-1) Al(iii) prepared in ultra-pure water was found to be 0.29% (n = 16). The Schiff base ligand could be used to determine ultra-trace aluminium from natural waters. Analysis of environmental certified reference materials showed good agreement with the certified values. The procedure was found to be equally applicable to both fresh water and saline solutions (including sea water) using either normal external calibration or the standard additions method.

Comparison of some newly synthesized chemically modified Amberlite XAD-4 resins for the preconcentration and determination of trace elements by flow injection inductively coupled plasma-mass spectrometry (ICP-MS).

XAD copolymer resins may be functionalized with heavy metal ion-selective ligands either by covalent linkage to the polymer backbone or by impregnation. These resins may be tailored to be specific for certain heavy metals by adjusting the retention and elution parameters. For the synthesis of immobilized Amberlite XAD-4 copolymer resins that are expected to preconcentrate a number of transition and heavy metals, the Schiff base method was chosen. For this purpose the copolymer was nitrated, reduced to the corresponding amine and converted to the imine compounds via a Schiff base reaction using different organic aldehyde compounds. The interactions of 8 elements (Cd, Co, Cu, Mn, Ni, Pb, U and Zn) with the resins were qualitatively investigated. Optimal pH for retention was typically 6-8 for most resins although one could be used at pH 5 and elution was achieved using 0.1 M HNO3. The resins were characterized by FTIR, SEM and elemental analysis. It was demonstrated that the resins could be used to preconcentrate ultra-trace analytes from natural waters, and analysis of environmental certified reference materials using FI-ICP-MS showed good agreement with the certified values. Metal retention capacities were also calculated using a batch system and were found to compare favorably with other resins reported in the literature.

Developments with anion exchange stationary phases for HPLC-ICP-MS analysis of antimony species.

Novel HPLC-ICP-MS methodologies are developed using strong anion exchange (Phenomenex SAX-SB) and weak anion exchange (Alltec HAAX) stationary phases in conjunction with a range of aqueous mobile phases to enable simultaneous separations of inorganic Sb(III), Sb(V) and organic trimethylantimony dichloride (TMSb) species in synthetic solutions. Optimum isocratic separations of inorganic Sb(V) and Sb(III) species are achieved using mobile phases comprised of ammonium tartrate under controlled pH conditions, and rapid pH gradient elution profiles are developed to facilitate separations of the Sb(V), Sb(III) and TMSb species in a single chromatographic run. Optimum peak resolution is achieved when using the 100 x 4.6 mm HAAX column at 20 degrees C and 100 mM ammonium tartrate mobile phases with a gradient from pH 3.0 to pH 1.2, although a system peak co-elutes with TMSb under these conditions and precludes quantitative analyses. Interestingly, the elution order of Sb(V), Sb(III) and TMSb species reverses when the temperature of the HAAX stationary phase is increased to 60 degrees C, and concurrent use of a less acidic pH gradient elution profile from pH 2.3 to pH 1.5 is shown to enable successful species separations whilst preventing occurrence of the co-eluting system peak. Limits of detection are achieved in the sub ng mL(-1) range using these novel HPLC-ICP-MS methodologies and provide scope for future environmental analysis applications.

Preconcentration and determination of trace elements with 2,6-diacetylpyridine functionalized Amberlite XAD-4 by flow injection and atomic spectroscopy.

An on-line flow injection method for the direct determination of trace elements in environmental samples is described. A mini-column packed with 2,6-diacetylpyridine functionalized Amberlite XAD-4 was used to preconcentrate and separate 8 trace metals (Cd, Co, Cu, Mn, Ni, Pb, U and Zn) from water and extracts from solid samples. The metals were eluted with 0.1 M HNO(3) directly to the detection system (either inductively coupled plasma-mass spectrometry (ICP-MS) or flame atomic absorption spectrometry (FAAS)). As well as demonstrating that the resin could be used to preconcentrate ultra-trace analytes from natural waters, it was also shown to work well at a pH of 5.5. Therefore, after treatment of sample digests with sodium fluoride, samples that contain extremely large concentrations of iron may be analysed for trace analytes without the excess iron overloading the capacity of the resin. To this end, the analytes Cd, Co, Cu and Ni were preconcentrated from acid extracts of certified soil/sediment samples and then eluted with nitric acid to be determined on-line. Limits of detection (3sigma) of Cd = 0.33 microg l(-1), Co = 0.094 microg l(-1), Cu = 0.34 microg l(-1), Mn = 0.32 microg l(-1), Ni = 0.30 microg l(-1), Pb = 0.43 microg l(-1), U = 0.067 microg l(-1) and Zn = 0.20 microg l(-1) for the FI-ICP-MS system and Cd = 22 microg l(-1), Co = 60 microg l(-1), Cu = 10 microg l(-1) and Ni = 4.8 microg l(-1) for the FI-FAAS system were obtained. Analysis of certified reference materials showed good agreement with the certified values using the two methods.

Uranium speciation in moorland river water samples: a comparison of experimental results and computer model predictions.

An on-line method has been developed for separating inorganic and organic bound uranium species present in river water samples. The method utilised a small chelating resin (Hyphan) column incorporated into the sample introduction manifold of an ICP-MS instrument. The method was evaluated for samples from rivers on Dartmoor (Devon, UK), an area of granite overlain with peat bogs. The results indicate that organic-uranium species form a major proportion (80%) of the total dissolved uranium present. Further work with synthetic water samples indicated that the level of dissolved organic carbon played a greater role in determining the level of organic-uranium species than did sample pH. Computer models for the water samples were constructed using the WHAM program (incorporating uranium data from the Nuclear Energy Agency Thermochemical Database project) in order to predict the levels of organic-uranium species that would form. By varying the proportion of humic and fulvic acids used in the humic component, predictions within 10% of the experimental results were obtained. The program did exhibit a low bias at higher pH values (7.5) and low organic carbon concentrations (0.5 microg ml(-1)), but under the natural conditions prevalent in the Dartmoor water samples, the model predictions were successful.

Metabolism, excretion, and pharmacokinetics of rosuvastatin in healthy adult male volunteers.

BACKGROUND: Rosuvastatin is a 3-hydroxy-3-methylglutaryl coenzyme A-reductase inhibitor, or statin, that has been developed for the treatment of dyslipidemia. OBJECTIVE: This study assessed the metabolism, excretion, and pharmacokinetics of a single oral dose of radiolabeled rosuvastatin ([14C]-rosuvastatin) in healthy volunteers. METHODS: This was a nonrandomized, open-label, single-day trial. Healthy adult male volunteers were given a single oral dose of [14C]-rosuvastatin 20 mg (20 mL [14C]-rosuvastatin solution, nominally containing 50 microCi radioactivity). Blood, urine, and fecal samples were collected up to 10 days after dosing. Tolerability assessments were made up to 10 days after dosing (trial completion) and at a follow-up visit within 14 days of trial completion. RESULTS: Six white male volunteers aged 36 to 52 years (mean, 43.7 years) participated in the trial. The geometric mean peak plasma concentration (C(max)) of rosuvastatin was 6.06 ng/mL and was reached at a median of 5 hours after dosing. At C(max), rosuvastatin accounted for approximately 50% of the circulating radioactive material. Approximately 90% of the rosuvastatin dose was recovered in feces, with the remainder recovered in urine. The majority of the dose (approximately 70%) was recovered within 72 hours after dosing; excretion was complete by 10 days after dosing. Metabolite profiles in feces indicated that rosuvastatin was excreted largely unchanged (76.8% of the dose). Two metabolites-rosuvastatin-5S-lactone and N-desmethyl rosuvastatin-were present in excreta. [14C]-rosuvastatin was well tolerated; 2 volunteers reported 4 mild adverse events that resolved without treatment. CONCLUSIONS: The majority of the rosuvastatin dose was excreted unchanged. Given the absolute bioavailability (20%) and estimated absorption (approximately 50%) of rosuvastatin, this finding suggests that metabolism is a minor route of clearance for this agent.

The effect of humic acids on the sequential extraction of metals in soils and sediments using ICP-AES and chemometric analysis.

The effect of humic acids on the sequential extraction of metals from various soils and sediments has been studied. A new multi-element extraction method optimised via experimental design has been employed. The method uses centrifugation to pass the extractant solution, at varying pH, through the sediment sample. The sequential leaches were collected and analysed by ICP-AES. Chemometric data processing was utilised to identify the composition of the physico-chemical components in order to characterise the sample. A sediment sample collected from Carnon River (Cornwall, UK) and a reference material (NIST 2711 agricultural soil) were spiked with humic acids and the sequential extraction scheme was used to monitor the changes in metal distribution. The method has proved a quick and reliable way to evaluate different sediment samples, and has potential as a new tool for environmental geochemistry analysis.

The effect of thermodynamic data on computer model predictions of uranium speciation in natural water systems.

Computer models have found widespread application in order to help elucidate and predict changes in environmental systems. One such application is the prediction of trace metal speciation in aqueous systems. This is achieved by solving a set of non-linear equations involving equilibrium constants for all the components in the system, within mass and charge balance constraints. In this study a comparison of the predicted uranium speciation from two computer programs, WHAM and PHREEQCI, is used to illustrate the effect variations in thermodynamic data can have on the models produced. Using the original thermodynamic data provided with the models, WHAM predicted the UO2(2+) ion as the major species (84%) while PHREEQCI predicted UO2(HPO4)2(2-) as the major species (86%). Substituting uranium data from the Nuclear Energy Agency Thermochemical Database project (NEA-TDB) into both programs produced similar results from each program, with UO2F+ predicted to dominate (68%) in a groundwater sample. Natural water samples often contain humic substances. The possible interaction of such substances with uranium was also modelled. The WHAM program includes a discreet site electrostatic humic substance model, however in order to use the PHREEQCI program to model humic substance interactions, a 'model fulvic acid' dataset was added to the program. These models predicted 85 to 98% uranium-humic substance species at neutral pH. This indicates that humic substances do need to be taken into account when modelling uranium speciation in natural water samples.

Optimization of a multielement sequential extraction method employing an experimental design approach for metal partitioning in soils and sediments.

The optimisation of a simple multielement extraction method employing an experimental design approach is described. The method uses centrifugation to pass one extractant solution at varying pH through a contaminated soil sample. The nature and concentration of the acid, rate of centrifugation and time, number of sequential leachates and the ratio of extractant volume: sample weight have been studied in order to obtain the optimum conditions for extraction. A fractional factorial experimental design was performed, and the results were used to identify significance which was then evaluated by carrying out a central composite experimental approach. Once optimum conditions had been obtained, sequential leaches were analysed by ICP-AES and chemometrics were employed to identify the composition of each component. Comparisons have been made with previous studies and tentative assignments, based on well defined separated fractions and percentage compositions for individual elements, used to identify the different physico-chemical components in the sample.