University of North Florida
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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

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Lake

Classification: Environmental -> sediment -> lake

Citations 4

"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

"Rapid Determination Of Mercury In Environmental Materials Using Online Microwave Digestion And Atomic-fluorescence Spectrometry"
Anal. Chim. Acta 1995 Volume 308, Issue 1-3 Pages 364-370
A. Morales-Rubio, Ml. Mena and C. W. McLeod*

Abstract: A 70-300 mg portion of environmental material was dispersed in HNO3/H2O (3:2) to form a slurry. A 400 µL portion of the slurry was injected into a 0.01 M HCl carrier stream (2.5 ml/min) and passed through a digestion coil (4 m x 0.8 mm i.d.) mounted in a microwave oven (20 W). The flow passed through a cooling coil (2 m x 0.8 mm i.d.) at 0°C and a degassing module and was merged with a reductant stream (2.5 ml/min) containing 3% SnCl2 in 15% HCl. After passing through the reduction coil (10 cm x 0.8 mm i.d.), the flow entered the gas-liquid separator. The Hg vapor was swept to the atomic-fluorescence detector with an air stream (600 ml/min) and Hg was determined at 253.7 nm. The calibration graph was linear for 2-10 µg/l Hg, the detection limit was 0.23 µg/l and the RSD (n = 3) were ~e;0.5% within the linear range. The method was validated by analyzing certified reference materials including soil, sewage sludge and lake sediment.
Mercury Fluorescence Sample preparation Reference material Microwave Online digestion Phase separator Slurry

"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

"Early Diagenesis Of Mercury In The Laurentian Great Lakes"
J. Great Lakes Res. 1995 Volume 21, Issue 4 Pages 574-586
Jane M. Matty and David T. Long

Abstract: The early diagenesis of mercury in deep lake environments was investigated by examining the distribution of mercury among waters and sediments from several depositional basins in the Laurentian Great Lakes. Partitioning of mercury among different sediment phases was examined by sequential chemical extraction (using procedures specifically designed for mercury). Mercury in porewaters and sediment extracts was analyzed by flow injection/hydride-generation atomic absorption spectroscopy. Results indicate that mercury is affected by early diagenesis at all of the sites studied. Much of the mercury is enriched in the surface layer of sediments, where it is primarily associated with organic matter and iron oxides. The redox cycling of iron and manganese influences the behavior of mercury; concentration profiles suggest that as oxides begin to dissolve in reduced sediments, nearly all of the adsorbed mercury is released. Organic matter decay also appears to release significant amounts of mercury. Porewater profiles suggest that most of the dissolved mercury released from decaying organic matter or from dissolving iron oxides may be taken up by freshly deposited organic matter and iron oxides in the near-surface layers. Much of the mercury that reaches the sediment column is thus recycled near the sediment-water interface, increasing both the residence time and the concentrations of mercury in surface sediments of these deep lake basins.
Mercury Spectrophotometry Sample preparation