University of North Florida
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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

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Hendrik Emons

Abbrev:
Emons, H.
Other Names:
Address:
Institute of Applied Physical Chemistry, Research Centre Juelich, Juelich D-52425, Germany
Phone:
+49-2461-615701
Fax:
+49-2461-612492

Citations 10

"Urinary Antimony Speciation By HPLC-ICP-MS"
J. Anal. At. Spectrom. 2001 Volume 16, Issue 1 Pages 20-25
Michael Krachler and Hendrik Emons

Abstract: This is the first study to report on the determination of Sb species in urine. To this end, HPLC was coupled online to an ICP-MS instrument using ultrasonic nebulization (USN) or hydride generation (HG) for sample introduction into the ICP-MS. The high chloride concentration in urine seriously hampered the chromatographic separation of Sb(v) and Sb(III) on the Dionex AS14 anion exchange column. Distinct signal suppression, shifting of retention times and severe peak broadening did not allow the application to urine samples. Progress to avoid these problems in HPLC-USN-ICP-MS could be made by employing a Hamilton PRP- x 100 anion;exchange column. However, Na eluting in the void volume of the column gave rise to a Na-induced peak overlapping with the Sb(v) signal when USN was used to aspirate the HPLC eluents into the plasma. Therefore, a HG system was placed between the HPLC and ICP-MS instrumentation to overcome this dilemma. Thus, Sb(v) and Sb(III) were separated in urine with the PRP- x 100 column using 20 mM EDTA at pH 4.7 as the mobile phase. Similarly, an ION-120 anion-exchange column was employed to separate trimethylantimony dichloride (TMSbCl2) and Sb(v) with a mobile phase containing 2 mM NH4HCO3 and 1 mM tartaric acid at pH 8.5. Detection limits of 20 ng 1-1, 12 ng L-1 and 8 ng L-1 for Sb(v), TMSbCl2 and Sb(III), respectively, could be established in a 1 + 2 diluted urine matrix. The developed HPLC-HG-ICP-MS method was applied to the speciation of Sb in the urine of occupationally exposed and nan-exposed subjects. Additionally, two lyophilised urine reference materials were investigated. Sb(v) was by far the predominant Sb species, followed by TMSbCl2. Only ultratraces of Sb(III), if any detectable, could be found. The sum of the concentrations of Sb(v), Sb(III) and TMSbCl2 in urine samples ranged between 51 and 78% of their total Sb concentrations.

"Potential Of High Performance Liquid Chromatography Coupled To Flow Injection Hydride Generation Atomic Absorption Spectrometry For The Speciation Of Inorganic And Organic Antimony Compounds"
J. Anal. At. Spectrom. 2000 Volume 15, Issue 3 Pages 281-285
Michael Krachler and Hendrik Emons

Abstract: This investigation was undertaken to elucidate the potential of high-performance liquid chromatography coupled to a hydride generation system connected to an atomic absorption spectrometer (HPLC-HG-AAS) as an element specific detector for the speciation of Sb(iii), Sb(v) and trimethylantimony dichloride (TMSbCl2). HG parameters were optimized specifically with regard to the Sb-species and yielded distinctly different optima for Sb(III) and Sb(V) as regards concentrations of NaBH4 and HCl. HCl (0.5% w/v) and of NaBH4 (0.6% w/v) proved to be a good compromise for optimum sensitivity for all Sb species. After optimization, signals for Sb(v) were still two times lower than for Sb(III) and TMSbCl2. Among the five anion exchange columns tested, the Dionex AS14 provided best results for the separation of Sb(V) and Sb(III) with 1.25 mM EDTA at pH 4.7. The ION-120 column was used to separate TMSbCl2 and Sb(V) with 2 mM NH4HCO3 and 1 mM tartaric acid at pH 8.5. When separating the three Sb-species in a single chromatographic run, sharp peaks for Sb(V) and Sb(III), but a very broad peak for TMSbCl2, were obtained. In all chromatographic separations the peaks could be baseline separated. Calibration curves were linear between 2 and at least 100 µg L-1. Detection limits of 0.4, 0.7, and 1.0 µg L-1 for TMSbCl2, Sb(III), and Sb(V) were obtained.

"Voltammetric Analysis With Microelectrodes"
GIT Fachz. Lab. 1996 Volume 40, Issue 3 Pages 204-206
Emons, H.

Abstract: The development and design of microelectrodes are described in this brief review, and the advantages of microelectrodes over macroelectrodes are illustrated by the corresponding voltammograms for 1 mM ferrocene in acetonitrile containing 0.1 M tetrabutylammonium hexafluorophosphate. Analytical applications of microelectrodes are discussed, with particular reference to in vivo measurements of catecholamines and other biochemicals, to measurements in media of low conductivity, and to detection in HPLC, FIA and capillary electrophoresis. (10 references).
Electrode Voltammetry HPLC Review

"Extraction Of Antimony And Arsenic From Fresh And Freeze-dried Plant Samples As Determined By HG-AAS"
Fresenius J. Anal. Chem. 2000 Volume 368, Issue 7 Pages 702-707
M. Krachler, H. Emons

Abstract: Six extraction media (acetic acid, EDTA, tetrabutylammonium hydroxide, NaOH, MeOH/H2O, acetonitrile/H2O) were tested for their ability to extract antimony (Sb) and arsenic (As) from freeze-dried poplar leaves, pine shoots and spruce shoots, as well as from a peat matrix. Additionally, the extraction efficiency of Sb and As in fresh and freeze-dried elder leaves and poplar leaves was compared. Total concentrations of Sb and As of aliquots (similar to 220 mg) of the freeze-dried samples were analyzed by flow injection hydride generation atomic absorption spectrometry (m-HG-AAS) after open vessel digestion with adequate mixtures of nitric, sulfuric, hydrochloric, and perchloric acid. Three reference materials GBW 07602 Bush Branches and Leaves, GBW 07604 Poplar Leaves, and SRM 1575 Pine Needles were analyzed with every batch of samples to ensure the accuracy and precision of the applied analytical procedures. The use of hydrofluoric acid in the digestion mixture leads to distinctly lower As values (down to 40%) than actual concentrations in the investigated plant materials. Extraction efficiencies were generally low and lower for Sb than for As. Solutions of 0.66 mol L-1 NaOH liberated highest amounts of Sb with similar to 10% for poplar leaves, and similar to 19% each for pine shoots and spruce shoots. Distinctly higher concentrations of As in NaOH extracts of poplar leaves (22%), pine shoots (32%), and spruce shoots (36%) were quantified. Extraction experiments resulted in yields of 7-9% from fresh elder and poplar leaves, respectively, and 8-13% for freeze-dried samples for Sb. The corresponding values for As were 10^-35% for the fresh material and 7-37% for the freeze-dried samples.
Speciation

"Convection-independent Detection With Voltammetric Single Micro-disc Electrodes"
Electroanalysis 1992 Volume 4, Issue 4 Pages 501-506
Frank-Michael Matysik, Hendrik Emons

Abstract: The design and construction are described of a new electrochemical flow cell incorporating a Pt micro-disc electrode that is positioned inside a narrow tube facing into the flowing stream. In experiments with ferrocene as model analyte and 0.1 M tetrapropylammonium perchlorate in acetonitrile as supporting electrolyte, it was shown that the flow rate dependence of the voltammetric signal was reduced as the electrode diameter was decreased from 114 µm, the limiting case being obtained at an electrode diameter of 0.7 µm. However, limits of detection were higher at electrodes smaller than 38 and 8 µm in diameter for continuous-flow and flow injection conditions, respectively. It is concluded that the optimum electrode size needs to be selected with respect to the analytical demands, i.e., the concentration. range of interest and convective characteristics of the experimental system.
Ferrocene Voltammetry Electrode Electrode Optimization Apparatus Detector

"Tensammetric And Indirect Amperometric Detection Of Phospholipids"
Electroanalysis 1991 Volume 3, Issue 6 Pages 543-551
Thomas Schmidt, Hendrik Emons

Abstract: The adsorption characteristics of phospholipids at the hanging-Hg-drop electrode (HMDE) were studied in acetonitrile - water - methanol solution Tensammetric flow injection detection at the HMDE was also studied systematically with different experimental parameters. The results were applied to the HPLC determination of phospholipids on a Separon SGX 5 (5 µm) column with acetonitrile - water - methanol (39:7:4) containing 0.05 M LiClO4 as the mobile phase and tensammetric detection at -1.8 V. The detection limits were 1.5 µg for strongly adsorbed compounds and 4 to 5 µg for other phospholipids. In addition, an indirect amperometric flow injection detection system was examined, based on the inhibition effect of adsorbed phospholipids on electrode reactions of quinol at vitreous-carbon-fiber electrodes. The detection limits were in the range 1.0 to 9.5 µg.
Phospholipids Amperometry HPLC Electrode Electrode Sensor Indirect

"Digestion Procedures For The Determination Of Antimony And Arsenic In Small Amounts Of Peat Samples By Hydride Generation-atomic Absorption Spectrometry"
Anal. Chim. Acta 2001 Volume 432, Issue 2 Pages 303-310
Michael Krachler, William Shotyk and Hendrik Emons

Abstract: Closed-pressurised and open vessel digestion procedures for the mineralisation of small amounts (similar to 100 mg) of peat samples have been developed and evaluated. The two trace elements As and Sb were quantified in the diluted digests by flow injection-hydride generation-atomic absorption spectrometry (FI-HC-AAS). Optimization of the analytical procedures was carried out with two bulk peat materials one of which was prepared as internal reference material. Both peat specimens were additionally characterized by instrumental neutron activation analysis with respect to their concentrations of As and Sb. Good agreement between instrumental neutron activation analysis (INAA) results and concentrations determined by HG-AAS were obtained. The use of adequate reference materials during the course of all experiments guaranteed precise and accurate results. Various acid mixtures with and without hydrofluoric acid were tested, because preliminary experiments revealed that HF in the digestion mixture leads to the formation of the gaseous AsF5 resulting in diminished recoveries of As when open vessel digestion procedures are employed. Avoiding HF for mineralisation of peat led to low recoveries for Sb because distinct amounts of Sb are associated with silicates. Closed-pressurised vessel digestion proved to be less effective compared to open vessel mineralisation. For successful quantification of both elements, two digestion procedures are needed, one without HF for As and another one with HF to liberate Sb from the silicates. The optimized open vessel digestion procedure was applied to the determination of ancient peat samples dating back to 9300 calendar years before present. Concentrations of both elements showed a broad spread with values ranging from 18 to 1500 and 300 to 5700 ng g-1 for Sb and As, respectively.

"Speciation Analysis Of Antimony By High-performance Liquid Chromatography Inductively Coupled Plasma Mass Spectrometry Using Ultrasonic Nebulization"
Anal. Chim. Acta 2001 Volume 429, Issue 1 Pages 125-133
Michael Krachler and Hendrik Emons

Abstract: The two inorganic Sb species Sb(III) and Sb(V) as well as trimethlyantimony dichloride (TMSbCl2) were separated by anion exchange chromatography. HPLC eluents were directly aspirated into the plasma of an ICP-MS using ultrasonic nebulization (USN) with membrane desolvation. Leaching of Sb from glass bottles, especially pronounced under alkaline conditions, distinctly increased background Sb-121 signals. The use of conventional HPLC syringes made of glass resulted in non reproducible blank signals for Sb(V). To overcome these problems, polyethylene bottles for the storage of mobile phases and plastic syringes for the injection of Sb compounds onto the analytical columns were employed. The analysis of Sb(III) standard solutions in the sub µg L-1 range prepared by dilution of stock standard solutions with high-purity water revealed that Sb(III) is easily oxidized to Sb(V) within a few hours. Deoxygenating the water for dilution of standards by flashing working standard solution with helium or using 1.25 mM EDTA - which served as mobile phase for the chromatographic separation - for the dilution of standards, no oxidation of Sb(III) was observed, at least for 8 h. USN parameters, such as the temperature of the heating area and of the desolvation area as well as the sweep gas flow rate were systematically optimized. Decreasing the USN heating temperature from the conventional settings of 140-80°C enhanced signal intensities by similar to 25% and caused no condensation of the aspirated mobile phase. After optimization detection limits for all three Sb species in the low ng L-1 range could be established, namely 14 ng L-1 for Sb(III), 12 ng L-1 for Sb(V) and 9 ng L-1 for TMSbCl2.
Speciation

"Optimized Procedure For The Determination Of Antimony In Lipid-rich Environmental Matrices By Flow Injection Hydride Generation Atomic Absorption Spectrometry"
Analyst 1999 Volume 124, Issue 6 Pages 923-926
Michael Krachler, Mechthild Burow and Hendrik Emons

Abstract: An analytical procedure for the reliable determination of Sb in digests of lipid-rich environmental matrices in the low ng L-1 range based on now injection hydride generation atomic absorption spectrometry (FI-HG-AAS)has been developed. Prior to HG-AAS, aliquots (250 to 320 mg) of dry samples were mineralized with 3 mL nitric acid and 0.5 mL of each sulfuric and perchloric acids in open digestion vessels made of glassy carbon in a heating block. Procedure detection and quantification limits of a previously developed procedure for the determination of Sb in plant materials by FI-HG-AAS were decreased with respect to the lower Sb concentrations in animal tissues, the sensitivity of the instrumental response was increased, and the composition of the acid digestion mixture was re-optimized for lipid-rich samples. The accuracy and precision of the developed procedure was evaluated by the analysis of the two reference materials Bovine Liver 1577a and Pig Kidney CRM 186. These reference materials have been additionally spiked with appropriate amounts of Sb to obtain recovery data. The solution detection limit (3s) in digested samples was 0.021 µg L-1, the detection limit for the whole procedure based on the dry powders was 7 pg g-1, the method quantification limit for a reliable determination of Sb was 23 pg g-1. The reproducibility of repetitive measurements was 6.0% at 0.1 µg Sb L-1 and 2.2% at 0.5 µg Sb L-1. Calibration curves were linear from 0.05 to 3 µg Sb L-1. To demonstrate the suitability of the developed method, concentrations of Sb have been determined in pigeon eggs (similar to 2 ng Sb g-1), as well as in bream livers (similar to 4 ng g-1) and in deer livers (similar to 5 to 8 ng g-1) from animals living in remote and urban-industrialized areas of Germany, respectively.
Speciation

"HPLC-HG-AAS And HPLC-ICP-MS For Speciation Of Arsenic And Antimony In Biomonitoring"
Am. Lab. News 2002 Volume 34, Issue 6 Pages 10-14
Krachler, M., Falk, K., and Emons, H.

Abstract: This article presents a comparison of the extractability of As and Sb species from biological matrices as well as two different detection principles that have been coupled on-line with HPLC separation of As and Sb species for the purpose of determining speciation patterns in specimens arising from environmental and human biomonitoring.
Arsenic Antimony Biological HPLC Method comparison Speciation