University of North Florida
Browse the Citations
-OR-

Contact Info

Stuart Chalk, Ph.D.
Department of Chemistry
University of North Florida
Phone: 1-904-620-1938
Fax: 1-904-620-3535
Email: schalk@unf.edu
Website: @unf

View Stuart Chalk's profile on LinkedIn

River

Classification: Environmental -> sediment -> river

Citations 15

"Coupling On-line Preconcentration By Ion-exchange With ETAAS. A Novel Flow Injection Approach Based On The Use Of A Renewable Microcolumn As Demonstrated For The Determination Of Nickel In Environmental And Biological Samples"
Anal. Chim. Acta 2000 Volume 424, Issue 2 Pages 223-232
Jianhua Wang and Elo Harald Hansen

Abstract: A novel way of exploiting flow injection/sequential injection (FIA/SIA) on-line ion-exchange pre-concentration with detection by electrothermal atomic absorption spectrometry (ETAAS) is described and demonstrated for the determination of trace-levels of nickel. Based on the use of a renewable microcolumn incorporated within an integrated µFI-system, the column is loaded with a defined volume of small beads of an SP Sephadex C-25 cation-exchange resin and subsequently exposed to a metered amount of sample solution. However, instead of eluting the retained analyte from the organic ion-exchange resin, the beads are along with 30 µL of carrier (buffer) solution transported via air segmentation directly into the graphite tube, where they are ashed during the pyrolysis and atomization process. The ETAAS determination is performed in parallel with the pre-concentration process of the ensuing sample. An enrichment factor of 72.1, a detection limit of 9 ng L-1, along with a sampling frequency of 12 h-1 were obtained with 150 s of sample loading time at a sample flow rate of 12 µL s-1 (corresponding to 0.72 mL min-1). The relative standard deviations were 3.4%. The procedure was validated by determination of the nickel contents in two certified reference materials and in a human urine sample.
Nickel Spectrophotometry Reference material Solvent extraction Preconcentration Column Sephadex Sequential injection Interferences Optimization

"A Flow Injection/hydride Generation System For The Determination Of Arsenic By Inductively-coupled Plasma Atomic Emission Spectrometry"
Anal. Chim. Acta 1984 Volume 161, Issue 1 Pages 275-283
R. R. Liversage and J. C. Van Loon, J. C. De Andrade

Abstract: After optimizing the concentration. of HCl and NaI in the test solution, the concentration. of NaBH4, sample and reductant volume and flow rate, Ar carrier-gas flow rate and r.f. power, As (10 to 1000 ppb) was determined in NBS orchard leaves, coal fly ash and river sediment and NRCC MESS-1 and BCSS-1 standard reference materials with good accuracy and precision by using an ARL 34000 Quantometer. The coefficient of variation (n = 10) at the 100-ppb level of As was 7.2%, and the detection limit was 1.4 ng for a 0.17 mL sample volume The calibration graph was rectilinear for 0.01 to 1 ppm of As. Cobalt, Ni, Ag, Au, Bi, Te and Sn interfered. About 200 injections h-1 were possible.
Arsenic Spectrophotometry Interferences Reference material

"Determination Of Cadmium, Copper And Lead In Environmental Samples. An Evaluation Of Flow Injection Online Sorbent Extraction For Flame Atomic Absorption Spectrometry"
Anal. Chim. Acta 1994 Volume 285, Issue 1 Pages 33-43
Renli Ma, Willy Van Mol and Freddy Adams*

Abstract: Lake, estuarine or river sediment, calcareous loam soil or coal fly ash were digested in a PTFE bomb with concentrated HF and HNO3 by heating until fuming. After cooling HClO4 was added, the bomb was sealed and heated for 8 h at 150°C. Silicates were removed by repeated addition of HF and HNO3 and evaporation to dryness and the residue was dissolved in HNO3, HCl and water. The solution was injected into a FIA system and mixed with 0.2% ammonium diethyldithiophosphate in 0.1 M citric acid adjusted to pH 1 with HNO3. Following pH dependent complexion with 0.1% diethylammonium-NN-diethyldithiocarbamate in 0.1 M acetic acid (described), 50 mM citric acid was added to mask Fe(III) and Mn(II). The complexes were sorbed onto C18 bonded silica gel (40-63 µm) in a conical extraction column, eluted with methanol and analyzed by AAS; elution rates and AAS nebulizer uptake rates are discussed. Calibration graphs of peak height were linear up to 50 µg/l of Cd, 300 µg/l of Cu and 1 mg/l of Pb with detection limits of 0.8, 1.4 and 10 µg/l, respectively, with a 20 s sample loading at 8.7 ml/min.
Cadmium Copper Lead Sample preparation Spectrophotometry Sample preparation Silica gel C18 Precipitation Solid phase extraction

"Determination Of Bismuth In Cod Muscle, Lake And River Sediment By Flow Injection Online Sorption Preconcentration In A Knotted Reactor Coupled With Electrothermal Atomic Absorption Spectrometry"
Anal. Chim. Acta 1997 Volume 354, Issue 1-3 Pages 7-13
Elissaveta Ivanova, Xiu-Ping Yan and Freddy Adams*

Abstract: A selective and robust flow injection (FI) on-line sorption separation and pre-concentration procedure was developed for the determination of bismuth in cod muscle, lake and river sediment samples by electrothermal atomic absorption spectrometry (ETAAS). The diethyldithiophosphate complex of bismuth is formed in 0.5-4% (v/v) HNO3 and adsorbed onto the inner walls of a PTFE knotted reactor. The complex is eluted with 30% (v/v) HCl and the eluate is directly introduced into a pyrolytically coated graphite tube without a preheating step. The ETAAS determination of the concentrated analyte is carried out in parallel with the next pre-concentration cycle. An enhancement factor of 74 and a detection limit (3s) of 3 ng l-1 along with a sampling frequency of 28 h-1 were achieved with a 60 s loading time at a sample flow rate of 5.2 mL min-1. The relative standard deviation was 3.4% for 0.1 µg L-1 (n=9). The analytical results for the Community Bureau of Reference (BCR) CRMs 280 (lake sediment) and 320 (river sediment) were in good agreement with the indicative values for the bismuth content. For the BCR CRM 422 (cod muscle) a value of 14 ng g-1 was found.
Bismuth Spectrophotometry Preconcentration Knotted reactor

"Determination Of Thallium In River Sediment By Flow Injection Online Sorption Preconcentration In A Knotted Reactor Coupled With Electrothermal Atomic Absorption Spectrometry"
Analyst 1997 Volume 122, Issue 7 Pages 667-671
Elissaveta Ivanova, Xiu-Ping Yan, Willy van Mol and Freddy Adams

Abstract: Sediment was digested by heating with HNO3/HF and then with HClO4. Aqueous bromine (up to 0.3%) was added to the final solution, which was made 2 M in HNO3. The resulting solution was pumped (4.8 ml/min) and mixed with a reagent stream (1.3 ml/min) of 0.05% ammonium pyrrolidinedithiocarbamate (APDC) before being loaded into a knotted PTFE reactor (100 cm x 0.5 mm i.d.). After a 30 s pre-concentration time, the reactor was washed with 0.1% H2SO4 and the Tl-APDC chelate was eluted with 45 µL ethanol (a diagram of the manifold used and details of the operating sequences employed are given). The eluate was analyzed for Tl by ET AAS at 276.8 nm using an Ir-modified graphite tube and pyrolysis and atomization temperatures of 600 and 1300°C, respectively (other operating conditions tabulated). The calibration graph was linear for 0.05-1.5 µg/l Tl, the detection limit was 15 ng/l and the RSD (n = 11) was 2.9%. The throughput was 26 samples/h. A flow injection online sorption pre-concentration electrothermal atomic absorption spectrometric (ETAAS) method mas developed for the determination of thallium, The Tl3+-tetramethplenedithiocarbamate (pyrrolidinedithiocarbamate) complex formed in strongly acidic medium (0-3 mol L-1 HNO3, 0-3 mol L-1 H2SO4, 0-2.5 mol L-1 HClO4 or 0-2 mol L-1 HCl) is sorbed on the inner malls of a PTFE knotted reactor (100 cm x 0.5 mm id) and quantitatively eluted with 45 µl of ethanol, The ETAAS determination is performed in parallel with the pre-concentration of the next sample, Using a pre-concentration time of 30 s and a sample loading rate of 4.8 mi min-1, an enhancement factor of 27 is obtained in comparison with direct injection of 45 pi of aqueous solution, The adsorption efficiency is 51%. The detection Limit (3s) is 0.015 µg L-1 and the precision (RSD) is 2.9% for 0.4 µg L-1 TI (It = II), The accuracy of the method is demonstrated by the analysis of a Community Bureau of Reference certified reference material 320 river sediment (indicative value for thallium concentration). 30 References
Thallium Sample preparation Spectrophotometry Preconcentration Knotted reactor Reference material Complexation Interferences

"Microanalytical Determination Of Metallic Constituents Of River Sediments"
Fresenius J. Anal. Chem. 1991 Volume 340, Issue 4 Pages 223-229
E. Ruiz, A. Echeandía and F. Romero

Abstract: The distribution of metallic constituents in torrential rivers as a function of the size particle cannot be frequently achieved by conventional analytical procedures, because of the lack of sufficient amounts of the fine fractions. For the study of river sediments in the Basque Country, microanalytical methods have been developed both for major (Na, K, Ca, Mg, Fe, Al, Si) and trace (Cu, Zn, Mn, Cr, Pb, Ni, Cd) components. Wet digestion in PTFE vessels at 140°C was done with 0.05 g sample using HNO-3-HClO-4-HF-H-3BO-3 or HNO-3-HClO-4, respectively. Further determinations were made by i) emission spectrometry (Na, K), ii) visible spectrophotometry (A1), iii) FIA (Fe, Si) and iv) AAS with flow spoiler (Ca, Mg, Cu, Zn, Mn) or graphite furnace (Cr, Pb, Ni, Cd). The proposed method has been checked with a standard sample obtaining mean values almost coincident with the certified ones and variation coefficients lower than 2% for major and 8% for trace components. Then it was applied to total samples and the fine fractions (<63 µm) of 26 samples of sediments from three torrential rivers. Replicated values with analogous variation coefficients were obtained. Some considerations on distribution of major and trace constituents as a function of particle size are also included.
Sodium Potassium Aluminum Iron Silicon Calcium Magnesium Manganese Copper Zinc Chromium Lead Nickel Cadmium Spectrophotometry Spectrophotometry Spectrophotometry Spectrophotometry Sample preparation Reference material

"Flow Injection Atomic Absorption Spectrometry For The Standardization Of Arsenic, Lead And Mercury In Environmental And Biological Standard Reference Materials"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 7 Pages 827-832
Gautam Samanta and D. Chakraborti

Abstract: Environmental and biological CRM were digested (details given). For the determination of Pb, prepared samples (50 µL) were injected into a carrier stream (1 ml/min) of 9% ammonium persulfate in 6% HNO3, which merged with a reducing stream (1 ml/min) of 8% NaBH4 in 1% NaOH then passed through a gas-liquid separator. A N2 flow (100 ml/min) carried hydrides to an AAS instrument for determination at 283.3 nm using an air-acetylene flame. For the determination of As, the carrier stream was 5 M HCl, the reducing stream was 1% NaBH4 containing 0.5% NaOH, the N2 flow rate was 200 ml/min and measurement was at 193.7 nm. For the determination of Hg, the carrier stream was 4% NaOH, the reducing stream was 0.5% SnCl2 and 0.035% L-cysteine in 1.5% H2SO4, the N2 flow rate was 50 ml/min and measurement was at 253.7 nm. A flame was not required for Hg determinations. The detection limits were 2 µg/l Pb, 1.8 µg/l As and 1.5 µg/l Hg, the quantitation limits were 7, 6 and 5 µg/l, respectively, and the corresponding RSD (n = 10) were 4%, 3% and 2%. Calibration ranges and recoveries are not stated. The sample throughput was 80/h in all cases. Results are tabulated for 12 CRM. The effects of interferents are also discussed. Results of a thorough study and application of flow injection atomic absorption spectrometry for the determination of As, Pb and Hg in parts per million to subparts per billion levels in environmental and biological samples have been described. Various standard reference materials from the National Bureau of Standards, USA, the National Institute of Standards and Technology, USA, the Community Bureau of Reference, Brussels, Belgium and the National Institute for Environmental Studies, Japan and Standard Chinese river sediment were used. By flow injection hydride generation AAS the standard reference materials were analyzed for As and Pb. Mercury was determined by cold vapor flow injection AAS from environmental and biological standard reference materials. The technique is fast, simple and highly sensitive. It takes only 30 s for each analysis from the digested solution. The detection limits of As, Pb and Hg are 1.8 µg L-1, 2.0 µg L-1 and 1.5 µg L-1, respectively. The results show good agreement with the certified values. 48 References
Arsenic Lead Mercury Spectrophotometry Sample preparation Spectrophotometry Reference material Interferences PPB Volatile generation Volatile generation

"Determination Of Total Mercury In Environmental And Biological Samples By Flow Injection Cold Vapor Atomic Absorption Spectrometry"
Spectrochim. Acta B 1996 Volume 51, Issue 14 Pages 1867-1873
James Murphy, Phil Jones and Steve J. Hill*

Abstract: Samples (~0.25 g) are weighed into 60 mL screw-capped PTFE digestion vessels, and biological samples are treated with 5 mL of HNO3 and 1 mL of H2O2 and environmental samples with 2.5 mL of HNO3, 2.5 mL of H2SO4 and 1 mL of H2O2. The vessels are then sealed and heated in a microwave oven for 1 min at medium power. Each digestate plus 2% HNO3/2% H2SO4 washings is diluted to known volume, the solution is degassed ultrasonically, and a portion is placed in an autosampler phial. A diagram of the manifold is presented; the sample (0.5 ml) is injected into a carrier stream of 3% HCl (12 ml/min) that subsequently merges with a stream of 0.2% NaBH4 solution in 0.05% NaOH (6.7 ml/min), and the liberated Hg is carried to a quartz cell in a stream of Ar. Calibration is effected with standard solutions containing up to 30 or 60 ng/ml of Hg, and the detection limit is 0.1 ng. The results for standard dogfish tissue and estuarine sediment agreed well with the certified values. The method was applied to river sediment and canned tuna.
Mercury Spectrophotometry Sample preparation Reference material Volatile generation

"Hydride-generation Flow Injection Using Graphite Furnace Detection - Emphasis On Determination Of Tin"
Spectrochim. Acta B 1992 Volume 47, Issue 5 Pages 701-709
Zhang Li, Susan McIntosh, Glen R. Carnrick and Walter Slavin*

Abstract: Hydride-forming analytes were separated from large volume of matrix by trapping the hydrides on a Pd-coated L'vov platform at low temperature before analysis by AAS. The Pd-treated stabilized-temp. platform furnace was used for in situ trapping and atomization of the analyte, and was at least 80% efficient for As, Bi, Ge, Sb, Se, Sn and Te. The method was tested by determining Sn in steel, river sediment, orchard leaves and bovine liver standard reference materials. The detection limit for Sn was 7 ng l-1, and the coefficient of variation was 31.5% at the 1.0 ng level. Other hydride-forming elements did not interfere.
Arsenic Bismuth Germanium Antimony Selenium Tellurium Tin Spectrophotometry Interferences Volatile generation Reference material Volatile generation

"The Determination Of Tin In Steel Samples By Flow Injection Hydride Generation Atomic Absorption Spectroscopy"
Spectrochim. Acta B 1992 Volume 47, Issue 7 Pages 897-906
Susan McIntosh, Zhang Li, Glen R. Carnrick and Walter Slavin*

Abstract: Copper, Ni and Co interfere in the cited determination. The interference occurs in the generation of hydride and not during the atomization of gaseous hydride. Tin was also determined in iron and river sediment samples. Hydride generation was in a saturated boric acid solution with a carrier solution of 2% HCl. Sample digestion in a pressure bomb was compared with that in aqua regia at 1 atmosphere. An Ar and O2 gas stream gas stream gave better sensitivity and peak symmetry than a pure Ar gas stream. The detection limit was 0.05 µg L-1 in a 500 µL sample with a coefficient of variation of 1 to 3% at higher concentration. of Sn. Conditions were studied for the determination of Sn in steel samples using flow injection, hydride generation, and atomic absorption spectroscopy. Interferences were found for the determination of Sn in steel samples and an investigation showed that the interferences occurred in the generation of the hydride, not in the atomization of the gaseous hydride. Conditions for the determination of Sn by flow injection hydride generation were improved by using integrated absorbance signals and by the addition of oxygen to the argon carrier gas stream. Typically, 500 µL of a 10 µg/L Sn standard provided an integrated absorbance signal greater than 0.5 A s. The method provided a detection limit of about 0.05 µg/L in a 500 µL sample. The precision ranged from 1 to 3% RSD at higher concentration levels of Sn. The method of additions yielded accurate results for several steel standard reference materials in those situations where the use of the standard calibration procedure was inadequate.
Tin Spectrophotometry Sample preparation Interferences Standard additions calibration Reference material Volatile generation Volatile generation

"The Fate Of Mercury Released From Prospecting Areas ('garimpos') Near Guarinos And Pilar De Goias (Brazil)"
An. Acad. Bras. Cienc. 1988 Volume 60, Issue 3 Pages 293-304
Choudhuri A.

Abstract: Analyses have been made of river water and of sediment up to 1500 m downstream to permit tracing of the mercury released from gold prospecting sites located in the State of Goias (Brazil). The determinations were performed by atomic emission spectroscopy coupled to a flow injection analysis system, operated in the reverse-FIA (r-FIA) configuration, and using either SnCl-2 or NaBH-4 as reducing agents. Mercury seems to be preferencially deposited in the sediment in specific points within 100 m of the site where the slip is discharged into the river drainage. The level of dissolved mercury in the river water was independent of the mercury content of the sediment and is in the range of 1.85 to 4.45 ng mL-1. According to these data, the principal environmental hazard from the amalgamation processing of gold appears to be due to mercury vapor released during the flaming process.
Mercury Spectrophotometry Amalgamation Reverse

"Interactions Of Manganese With The Nitrogen-cycle Alternative Pathways To Dinitrogen"
Geochim. Cosmochim. Acta 1997 Volume 61, Issue 19 Pages 4043-4052
George W. Luther, III, Bj&oslash;rn Sundby, Brent L. Lewis, Paul J. Brendel and Norman Silverberg

Abstract: The conversion of combined nitrogen (ammonia, nitrate, organic nitrogen) to dinitrogen (N-2) in marine sediments, an important link in the global nitrogen cycle, is traditionally assumed to take place only via the coupled bacterial nitrification-denitrification process. We provide field and laboratory evidence that N-2 can also be produced by the oxidation of NH3 and organic-N with MnO2 in air. The reduced manganese formed in this reaction readily reacts with O-2, generating reactive Mn(III, TV) species to continue the oxidation of NH3 and organic-N to N-2. Free energy calculations indicate that these two reactions are more favorable as a couple than the oxidation of organic matter by O-2 alone. We also provide field evidence consistent with the reduction of NO3- to N-2 by dissolved Mn2+. These two reactions involving nitrogen and manganese species can take place in the presence and absence of O-2, respectively. Our field evidence suggests that the oxidation of NH3 and organic-N to N-2 by MnO2 in the presence of O-2 can outcompete the oxidation of NH3 to NO3- in Mn-rich continental margin sediments and thereby short-circuit the nitrification/denitrification process. The MnO2 catalyzed reaction may account for up to 90% of the N-2 formation in continental margin sediments, the most important N-2 producing environments in the marine N cycle. The oxidation of NH3 and organic-N by MnO2 in the presence of O-2 can explain why N-2 can form in oxic sediments; it can also explain why denitrification rates measured by acetylene inhibition and labeled tracers can give lower estimates than direct measurements of N-2 production. Copyright (C) 1997 Elsevier Science Ltd. 43 References
Nitrogen Catalysis

"Liquid Chromatographic Method For Quantitation Of Glyphosate And Metabolite Residues In Organic And Mineral Soils, Stream Sediments And Hardwood Foliage"
J. AOAC Int. 1989 Volume 72, Issue 2 Pages 355-360
Thompson DG, Cowell JE, Daniels RJ, Staznik B, MacDonald LM

Abstract: Soil, sediment, foliage and deposit collectors (polyethylene sheets) were extracted with aqueous 0.5 M NH3 and the extract was applied to an AG 1-X8 anion-exchange column, with elution with 0.5 M NH4HCO3. After removal of bicarbonate by repeated evaporation and dissolution in water, further cleanup was effected on a Dowex 50W-X8 cation-exchange column. The aqueous eluate was evaporated to dryness and the residue was dissolved in 5 mM KH2PO4 for HPLC on a column (10 cm x 4.6 mm) of Aminex A-9 equipped with a guard column of the same material and operated at 50°C with 5 mM KH2PO4 (pH 1.9) buffer in aqueous 4% methanol as mobile phase (0.5 mL min-1). After post-column derivatization with ninhydrin at 100°C, glyphosate (I) and its metabolite aminomethylphosphonic acid (II) were detected at 570 nm. Calibration graphs were rectilinear for 0.05 to 3.0 µg of I and 12.5 to 750 ng of II, and detection limits ranged from 0.01 to 0.1 µg g-1.
Glyphosate LC Sample preparation Column Dissolution rate Post-column derivatization Calibration Detection limit Extraction

"Determination Of Aluminum In Suzhou River Sediment With Flow Injection Spectrophotometry"
Shanghai Huanjing Kexue 1987 Volume 6, Issue 8 Pages 24-31
Zhang, Guoying

Abstract: A flow injection spectrophotometric method for determining aluminum in sediments of Suzhon River, China, had good reproducibility and accuracy with a recovery rate of 84-101%. The method uses Chrome Azurol S as the color developing agent, does not require vacuum degassing, and has a wide linearity range. It takes 1 h to analyze 100 samples.
Aluminum Spectrophotometry

"Determination Of Aluminum In River Sludge By Dual-beam Spectrophotometric - FIA"
Yankuang Ceshi 1991 Volume 10, Issue 3 Pages 197-199
Zhao, Z.Y.;Chen, H.

Abstract: Sample (0.5 g) was digested with HNO3 - HF - HClO4 and then diluted to 50 mL with H2O; a portion of the solution (200 µL) was injected and carried by a stream of buffer (8.28 g of Na acetate and 3.5 g of ascorbic acid in 25 mL of H2O) to react with 0.005 to 0.01% Chrome Azurols (5.8 mL min-1) in a 100-cm reaction tube followed by dual-beam spectrophotometric detection at 590 nm (detector cells linked by a 10-cm tube). Detection limit was 0.04 ppm; coefficient of variation was 0.8%. Interferences were overcome. Sampling frequency was 80 to 90 samples per h. Sensitivity of the method was twice as high as the conventional single-beam technique. Satisfactory results were compared with those obtained by AAS.
Aluminum Spectrophotometry Buffer Interferences Sensitivity