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Dive into the research topics where Jared G. Panther is active.

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Featured researches published by Jared G. Panther.


Analytical Chemistry | 2010

New Diffusive Gradients in a Thin Film Technique for Measuring Inorganic Arsenic and Selenium(IV) Using a Titanium Dioxide Based Adsorbent

William W. Bennett; Peter R. Teasdale; Jared G. Panther; David T. Welsh; Dianne F. Jolley

A new diffusive gradients in a thin film (DGT) technique, using a titanium dioxide based adsorbent (Metsorb), has been developed and evaluated for the determination of dissolved inorganic arsenic and selenium. As(III), As(V), and Se(IV) were found to be quantitatively accumulated by the adsorbent (uptake efficiencies of 96.5-100%) and eluted in 1 M NaOH (elution efficiencies of 81.2%, 75.2%, and 88.7%). Se(VI) was not quantitatively accumulated by the adsorbent (<20%). Laboratory DGT validation experiments gave linear mass uptake over time (R(2) >or= 0.998) for As(III), As(V), and Se(IV). Consistent uptake occurred over pH (3.5-8.5) and ionic strength (0.0001-0.75 mol L(-1) NaNO(3)) ranges typical of natural waters, including seawater. Field deployments of DGT probes with various diffusive layer thicknesses confirmed the use of the technique in situ, allowing calculation of the diffusive boundary layers and an accurate measurement of inorganic arsenic. Reproducibility of the technique in field deployments was good (relative standard deviation <8%). Limits of detection (4 day deployments) were 0.01 microg L(-1) for inorganic arsenic and 0.05 microg L(-1) for Se(IV). The results of this study confirmed that DGT with Metsorb was a reliable and robust method for the measurement of inorganic arsenic and the selective measurement of Se(IV) within useful limits of accuracy.


Environmental Science & Technology | 2010

Titanium dioxide-based DGT technique for in situ measurement of dissolved reactive phosphorus in fresh and marine waters.

Jared G. Panther; Peter R. Teasdale; William W. Bennett; David T. Welsh; Huijun Zhao

A new diffusive gradients in a thin film (DGT) technique for measuring dissolved reactive phosphorus (DRP) in fresh and marine waters is reported. The new method, which uses a commercially available titanium dioxide based adsorbent (Metsorb), was evaluated and compared to the well-established ferrihydrite-DGT method (ferrihydrite cast within the polyacrylamide gel). DGT time-series experiments showed that the mass of DRP accumulated by Metsorb and ferrihydrite was linear with time when deployed in simple solutions. Both DGT methods showed predictable uptake across the pH (4.0-8.3) and ionic strength (0.0001-1 mol L(-1) NaNO(3)) ranges investigated, and the total capacity of the Metsorb binding phase (∼40,000 ng P) was 2.5-5 times higher than the reported total capacity of the ferrihydrite binding phase. The measurement of DRP in synthetic freshwater and synthetic seawater by Metsorb-DGT over a 4 day deployment period showed excellent agreement with the concentration of DRP measured directly in solution, whereas the ferrihydrite-DGT method significantly underestimated (23-30%) the DRP concentration in synthetic seawater for deployment times of two days or more. Field deployments of Metsorb-DGT samplers with various diffusive layer thicknesses allowed accurate measurement of both the diffusive boundary layer thickness and DRP concentration in situ. The Metsorb-DGT method performs similarly to ferrihydrite-DGT for freshwater measurements but is shown to be more accurate than the ferrihydrite method for determining DRP in seawater.


Analytical Chemistry | 2011

Speciation of dissolved inorganic arsenic by diffusive gradients in thin films: selective binding of AsIII by 3-mercaptopropyl-functionalized silica gel

William W. Bennett; Peter R. Teasdale; Jared G. Panther; David T. Welsh; Dianne F. Jolley

A diffusive gradients in thin films (DGT) technique for selectively measuring As(III) utilizes commercially available 3-mercaptopropyl-functionalized silica gel. Deployment of the new technique alongside the Metsorb-DGT for total inorganic arsenic allows the calculation of As(III) directly and As(V) by difference. Uptake of As(III) by mercapto-silica was quantitative and elution with a mixture of 1 mol L(-1) HNO(3) and 0.01 mol L(-1) KIO(3) gave a recovery of 85.6 ± 1.7%. DGT validation experiments showed linear accumulation of As(III) over time (R(2) > 0.998). Accumulation was unaffected by varying ionic strength (0.0001-0.75 mol L(-1) NaNO(3)) and pH (3.5-8.5). Deployment of mercapto-silica DGT and Metsorb DGT in seawater spiked with As(III) and As(V) demonstrated the ability of the combined approach to accurately quantify both species in the presence of potential competing ions. Ferrihydrite DGT, which has been previously reported for the measurement of total inorganic arsenic, was evaluated in seawater and shown to underestimate both As(III) and As(V) at longer deployment times (72 h). Reproducibility of the new mercapto-silica DGT technique was good (relative standard deviations < 9%), and the average method detection limit was sufficiently low to allow quantification of ultratrace concentrations of As(III) (0.03 μg L(-1); 72 h deployment).


Analytica Chimica Acta | 2008

Development and application of the diffusive gradients in thin films technique for the measurement of total dissolved inorganic arsenic in waters.

Jared G. Panther; Kathryn P. Stillwell; Kipton J. Powell; Alison J. Downard

The diffusive gradients in thin films (DGT) technique, utilizing an iron-hydroxide adsorbent, has been investigated for the in situ accumulation of total dissolved inorganic As in natural waters. Diffusion coefficients of the inorganic As(V) and As(III) species in the polyacrylamide gel were measured using a diffusion cell and DGT devices and a variety of factors that may affect the adsorption of the As species to the iron-hydroxide adsorbent, or the diffusion of the individual As species, were investigated. Under conditions commonly encountered in environmental samples, solution pH and the presence of anions, cations, fulvic acid, Fe(III)-fulvic acid complexes and colloidal iron-hydroxide were demonstrated not to affect uptake of dissolved As. To evaluate DGT as a method for accumulation and pre-concentration of total dissolved inorganic As in natural waters, DGT was applied to two well waters and a river water that was spiked with As. For each sample, the concentration obtained with use of DGT followed by measurement by hydride generation atomic absorption spectrometry with a Pd modifier (HG-AAS) was compared with the concentration of As measured directly by HG-AAS. The results confirmed that DGT is a reliable method for pre-concentration of total dissolved As.


Talanta | 2013

Titanium dioxide-based DGT for measuring dissolved As(V), V(V), Sb(V), Mo(VI) and W(VI) in water

Jared G. Panther; Ryan Robert Stewart; Peter R. Teasdale; William W. Bennett; David T. Welsh; Huijun Zhao

A titanium dioxide-based DGT method (Metsorb-DGT) was evaluated for the measurement of As(V), V(V), Sb(V), Mo(VI), W(VI) and dissolved reactive phosphorus (DRP) in synthetic waters. Mass vs. time DGT deployments at pH 6.06 (0.01 mol L(-1) NaNO3) demonstrated linear uptake of all analytes (R(2) ≥ 0.994). Diffusion coefficients measured using a diffusion cell were in reasonable agreement with diffusion coefficients measured using DGT samplers (DCell/DDGT=0.82-1.10), although a systematic difference was apparent. The Metsorb-DGT method was independent of ionic strength (0.001-0.7 mol L(-1) NaNO3 at pH 7.1) for the measurement of all analytes (CDGT/CSol=0.88-1.11) and, with the exception of V(V), the method was independent of pH (3.98-8.24, 0.01 mol L(-1) NaNO3), indicated by CDGT/CSol values in the range 0.88-1.13 for short-term deployments (up to 10h). For V(V) at pH 3.98, Metsorb-DGT underestimated the solution concentration by 17%, presumably due to weak binding of the VO2(+) species. The Metsorb-DGT and ferrihydrite-DGT (in situ precipitated ferrihydrite) methods were compared by deploying samplers in synthetic freshwater (pH 7.20, conductivity 223 μS cm(-1)) and synthetic seawater (pH 8.3. salinity 34.6) for up to four days. For synthetic freshwater, CDGT/CSol values between 0.87-1.17 were obtained for all analytes measured by the Metsorb-DGT method over the deployment period. For ferrihydrite-DGT, CDGT/CSol values between 0.97-1.23 were obtained for As(V), V(V), W(VI) and DRP. However, Mo and Sb(V) showed reduced uptake and CDGT/CSol values were in the range 0.18-1.14 and 0.39-0.98, respectively. In synthetic seawater deployments, Metsorb-DGT was capable of measuring As(V), V(V), Sb(V), W(VI) and DRP for up to 4 days (CDGT/CSol=0.89-1.26), however, this method was not capable of measuring Mo for deployment times >4h (CDGT=0.27-0.72). For ferrihydrite-DGT, CDGT/CSol values in the range 0.92-1.16 were obtained for As(V), V(V) and DRP, however, Mo(VI), Sb(V) and W(VI) could not be measured to within 15% of the solution concentration (CDGT/CSol 0.02-0.83).


Analytica Chimica Acta | 2011

Comparing dissolved reactive phosphorus measured by DGT with ferrihydrite and titanium dioxide adsorbents: Anionic interferences, adsorbent capacity and deployment time

Jared G. Panther; Peter R. Teasdale; William W. Bennett; David T. Welsh; Huijun Zhao

Two adsorbents (Metsorb and ferrihydrite) used in binding layers with the diffusive gradients in a thin film technique were evaluated for the measurement of dissolved reactive phosphorous (DRP) in synthetic and natural waters. Possible interferences were investigated with Cl(-) (up to 1.35 mol L(-1)) and SO(4)(2-) (up to 0.056 mol L(-1)) having no affect on either DGT binding layer, and HCO(3)(-) (up to 5.7 mmol L(-1)) having no effect on Metsorb-DGT, over 4 days. However, HCO(3)(-) interfered with the ferrihydrite-DGT measurement at concentrations typical of many natural waters (≥0.7 mmol L(-1)) after a deployment period of 1-2 days. The capacity of the Metsorb binding phase for DGT response was ∼37,000 ng P, whereas the capacities of a low-mass (17.8 mg of adsorbent per DGT sampler) and high-mass (29.2mg of adsorbent per DGT sampler) ferrihydrite binding phase were substantially lower (∼15,000 ng P and ∼25,000 ng P, low-mass and high-mass, respectively). Increasing the capacity of the ferrihydrite adsorbent allowed the ferrihydrite-DGT to be utilized for up to 3 days before interference by HCO(3)(-) was observed. Seawater deployments demonstrated that even high-capacity ferrihydrite-DGT devices underestimated the DRP concentration by 37%, whereas Metsorb-DGT measurements were accurate. The Metsorb-DGT is superior to the ferrihydrite-DGT for determining DRP over deployment times greater than 1 day and in waters with ≥0.7 mmol L(-1) HCO(3)(-). Based on the experience obtained from this detailed validation process, the authors propose a number of key requirements that need to be considered when developing new DGT binding layers, with testing the performance over longer deployment times being critical.


Environmental Science & Technology | 2012

Investigating Arsenic Speciation and Mobilization in Sediments with DGT and DET: A Mesocosm Evaluation of Oxic-Anoxic Transitions

William W. Bennett; Peter R. Teasdale; Jared G. Panther; David T. Welsh; Huijun Zhao; Dianne F. Jolley

Mobilization of arsenic from freshwater and estuarine sediments during the transition from oxic to anoxic conditions was investigated using recently developed diffusive sampling techniques. Arsenic speciation and Fe(II) concentrations were measured at high resolution (1-3 mm) with in situ diffusive gradients in thin films (DGT) and diffusive equilibration in thin films (DET) techniques. Water column anoxia induced Fe(II) and As(III) fluxes from the sediment. A correlation between water column Fe(II) and As(III) concentrations was observed in both freshwater (r(s) = 0.896, p < 0.001) and estuarine (r(s) = 0.557, p < 0.001) mesocosms. Porewater sampling by DGT and DET techniques confirmed that arsenic mobilization was associated with the reductive dissolution of Fe(III) (hydr)oxides in the suboxic zone of the sediment; a relationship that was visible because of the ability to measure the coincident profiles of these species using combined DGT and DET samplers. The selective measurement of As(III) and total inorganic arsenic by separate DGT samplers indicated that As(III) was the primary species mobilized from the solid phase to the porewater. This measurement approach effectively ruled out substantial As(V) mobilization from the freshwater and estuarine sediments in this experiment. This study demonstrates the capabilities of the DGT and DET techniques for investigating arsenic speciation and mobilization over a range of sediment conditions.


Environmental Science & Technology | 2012

DGT Measurement of Dissolved Aluminum Species in Waters: Comparing Chelex-100 and Titanium Dioxide-Based Adsorbents

Jared G. Panther; William W. Bennett; Peter R. Teasdale; David T. Welsh; Huijun Zhao

Aluminum is acutely toxic, and elevated concentrations of dissolved Al can have detrimental effects on both terrestrial and aquatic ecosystems. Robust analytical methods that can determine environmentally relevant Al fractions accurately and efficiently are required by the environmental monitoring community. A simple, robust passive sampling method, the diffusive gradients in thin films (DGT) technique, was evaluated for the measurement of dissolved Al species in freshwater and marine water using either Chelex-100 or Metsorb (a titanium dioxide-based binding agent) as the adsorbent. Mass vs time DGT deployments at pH 5.05 (Al(3+) and Al(OH)(2+) dominate) and 8.35 (Al(OH)(4)(-) dominates) demonstrated linear uptake of Al (R(2) = 0.989 and 0.988, respectively) for Metsorb. Similar deployments of Chelex-DGT showed linear uptake at pH 5.05 (R(2) = 0.994); however, at pH 8.35 the mass of Al accumulated was 40-70% lower than predicted, suggesting that Chelex-100 is not suitable for Al measurements at high pH. The Metsorb-DGT measurement was independent of pH (5.0-8.5) and ionic strength (0.001-0.7 mol L(-1) NaNO(3)), whereas the Chelex-DGT measurement was only independent of ionic strength at pH 5.0. At pH 8.4, increasing ionic strength led to considerable underestimation (up to 67%) of Al concentration. Deployments of Metsorb-DGT (up to 4 days) in synthetic freshwater (pH range 5.4-8.1) and synthetic seawater (pH 8.15) resulted in linear mass uptakes, and the concentration measured by DGT agreed well with solution concentrations. Conversely, deployment of Chelex-DGT in synthetic seawater and freshwater (pH ≥7.7 Al(OH)(4)(-) dominant species) resulted in a decrease in accumulated mass with increasing deployment time. In situ field evaluations in fresh, estuarine, and marine waters confirmed that Metsorb-DGT was more accurate than Chelex-DGT for the measurement of dissolved Al in typical environmental waters.


Analytical Chemistry | 2008

Perfluorosulfonated ionomer-modified diffusive gradients in thin films: tool for inorganic arsenic speciation analysis.

Jared G. Panther; Kathryn P. Stillwell; Kipton J. Powell; Alison J. Downard

A new concept in speciation analysis based on the diffusive gradients in thin films (DGT) technique is described. By use of two sets of DGT devices, one set with perfluorosulfonated ionomer (Nafion) diffusive membranes and the other with polyacrylamide, anionic and uncharged analytes can be fractionated on the basis of charge. The dual device method is applied to speciation analysis of dissolved inorganic arsenic species. Over the environmentally significant pH range, inorganic As(III) exists as neutral H(3)AsO(3), whereas As(V) is present as anionic H(2)AsO(4)(-) and HAsO(4)(2-). The measured diffusion coefficient of As(III) through the negatively charged Nafion membrane is significantly larger than that of the As(V) species, whereas diffusion rates are similar through polyacrylamide diffusive gels. Hence, after simultaneously deploying DGT devices with and without Nafion membranes, measurement of the amount of accumulated As in each type of device enables the concentration of both oxidation states to be determined.


Analytica Chimica Acta | 2003

Lability of metal ion-fulvic acid complexes as probed by FIA and DGT: a comparative study

Alison J. Downard; Jared G. Panther; Young-Chool Kim; Kipton J. Powell

Two kinetic-based analytical techniques with very different time constants (flow injection analysis, FIA and diffusive gradients in thin films, DGT) have been compared in a study of metal ion lability in the systems Al 3+ -FA and Cu 2+ -FA (fulvic acid, FA). Flow injection analysis used an in-line micro-column of chelating ion exchanger to capture the labile metal fraction during the short contact time, 1-3 s, with the injected sample. The moderately labile and inert metal fractions were rejected by the ion exchanger but the former gave a colorimetric reaction down-line. The labile fraction was quantified by subsequent elution of captured metal ions and down-line analysis. The chelating resins used were oxine-derivatised fractogel (for Al 3+ ) and oxine-derivatised controlled-pore glass (for Cu 2+ ). Diffusive gradients in thin films utilised cross-linked polyacrylamide films as the diffusive barrier and Chelex-100 to capture the diffusing metal ions that are labile on the experiment time-scale (min). Diffusion coefficients, D, for metal-FA systems at different metal:FA ratios were measured independently in a diffusion cell. They indicated that for both the labile (Cu 2+ -FA) and slowly labile (Al 3+ -FA) systems the metal ion diffuses at a similar velocity to the FA, even when the total metal ion concentration exceeds the capacity of FA to bind metal ions in non-labile forms (FA complexation capacity, CC). Complexation capacity was used as a basis for comparison of the two techniques. It was observed that for the less labile Al 3+ -FA system, the DGT-labile Al 3+ equated to the sum of the labile + moderately labile fractions determined by FIA. For the Cu 2+ -FA system the CC determined by DGT was smaller than that determined by FIA (significant at IS.D.). Further, the results indicated that D values measured for labile metal-FA complexes in a diffusion cell may not be appropriate for interpretation of diffusion processes that occur in the DGT experiment.

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Alison J. Downard

MacDiarmid Institute for Advanced Materials and Nanotechnology

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Chang Liu

Chinese Academy of Sciences

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Taicheng An

Guangdong University of Technology

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