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

Olivier F. X. Donard

Abbrev:
Donard, O.F.X.
Other Names:
Address:
Laboratory Chim Analytical, Bioorgan and Environm Cnrs, University of Pau and Pays Adour, Ep 132, F-64000 Pau, France
Phone:
NA
Fax:
NA

Citations 6

"Microwave Assisted Reduction Of Se(VI) To Se(IV) And Determination By HG/FI-ICP/MS For Inorganic Selenium Speciation"
Talanta 1998 Volume 45, Issue 5 Pages 1023-1029
Riansares Muñoz Olivas and O. F. X. Donard*

Abstract: Speciation of inorganic selenium using hydride generation method is a widespread analytical method nowadays. However, a reduction step of Se(VI) to Se(IV) is necessary as the hydride-forming species is HSeO3- (oxidation state+IV). This paper describes the development of a batch assisted microwave system allowing a rapid (<5 min) conversion of Se(VI) to Se(IV). Hydride generation is performed by a flow injection system and detection by ICP/MS. Detection limits of 6 and 8 pg for Se(IV) and for Se(VI) (by using a sample loop of 200 µL) respectively have been achieved. This method has been validated by participating in a European certification exercise for inorganic Se speciation in aqueous solutions.
Selenium(IV) Selenium(VI) Selenium, inorganic Mass spectrometry Speciation

"Chemical Availability Of Mercury In Stream Sediments From The Almaden Area, Spain"
J. Environ. Monit. 2000 Volume 2, Issue 4 Pages 360-366
R. C. Rodr&iacute;guez Mart&iacute;n-Doimeadios, J. C. Wasserman, L. F. Garc&iacute;a Bermejo, D. Amouroux, J. J. Berzas Nevado and O. F. X. Donard

Abstract: The chemical speciation, fractionation and availability of mercury in sediments from a cinnabar mining area (Almaden, Spain) was studied with different extraction and analytical procedures, in order to determine the degree to which the ecosystem is harmed by this pollutant. Three total extraction procedures, a sequential extraction and the speciation of organo-mercury compounds were performed in nine sediment samples. In the study area, although concentrations of mercury can be extremely high (up to 1000 mg kg-1), no organo-mercury compounds were detected (< 2 µg kg-1) and the availability of this element seems restricted. One of the methods for total extraction presented considerably lower recovery in Almadens sediments, yet the results were controlled with certified reference materials. This disagreement was attributed to the fact that the mercury is in a refractory form. Sequential extraction was able to show that most of the mercury is associated with sulfides (probably as metacinnabar) or in the residual refractory phase (probably as red cinnabar).

"Sensitive Determination Of Selenium By Inductively Coupled Plasma Mass Spectrometry With Flow Injection And Hydride Generation In The Presence Of Organic Solvents"
J. Anal. At. Spectrom. 1995 Volume 10, Issue 10 Pages 865-870
Riansares Mu&ntilde;oz Olivas, C. R. Qu&eacute;tel and O. F. X. Donard

Abstract: Two sample introduction methods, viz., pneumatic nebulization and hydride generation via a flow injection system were used to study the optimum conditions for Se determination. The effect of organic solvents in polyatomic interferences (40Ar, 37Cl, 40Ar, 38Ar and 40Ar2H2) suppression and signal enhancement were investigated. The organic solvents studied were: methanol, ethanol, propanol, acetone and acetonitrile. A SCIEX Perkin Elmer 5000 spectrometer was used. The pneumatic nebulization flow rate ranged from 0.95-1.05 L/min and the Ar flow rate for hydride generation was similar (1.05-1.1 L/min); other operating conditions are tabulated. Under optimum conditions (NaBH4 = 0.2%, pH = 1, methanol load = 6%) for flow injection hydride-generation ICP-MS a detection limit of 1 pg of Se was obtained using a 200 µL sample. The average RSD was 2%. The method was applied to estuarine water and Se levels ranged from 5 to 70-80 ng/L. Validation was via an EC certification campaign.
Selenium Estuarine Mass spectrometry Volatile generation Optimization Organic solvent Method comparison Interferences Signal enhancement Volatile generation

"Aqueous Ethylation Of Organotin Compounds In Simple Solution For Speciation Analysis By Cryofocussing And Detection By Atomic Absorption Spectrometry - Comparison With Hydride Generation"
Fresenius J. Anal. Chem. 1995 Volume 351, Issue 2-3 Pages 230-236
F. M. Martin and O. F. X. Donard

Abstract: A 23 factorial experimental design has been used to determine the optimum reaction conditions for organotin ethylation in simple aqueous solutions for speciation by Cryogenic Trapping/ Gas Chromatography/Atomic Absorption Spectrometry (CT/GC/AAS). The factors chosen and their levels of variation (- and +) were the pH of the solution (levels 3 and 5), the amount of NaBEt4 added (levels 1 and 9 mg) to the organotins and the time of ethylation reaction (levels 10 and 20 min). Optimum conditions were investigated for monomethyltin (MMT), diethyltin (DET) and dibutyltin (DBT) in mixed solution at a concentration of 10 ng of each Sn compound in 50 mL of solution (200 ng L-1). The influence of the different factors on the yield of the ethylation reaction in the ranges investigated depends on the degree of substitution and the nature of the alkyl groups of the organotins. The ethylation reaction for DET and DBT is more efficient at high pH levels, MMT gives higher yields at lower pH. Both MMT and DET require a high amount of reagent, while reagent concentration has no real influence on the DBT signal. Comparison of hydride generation and ethylation as derivatization procedures for organotin speciation has been performed in simple solutions. Under these analytical conditions, hydride generation is shown to be slightly more sensitive than ethylation by a factor of 1.4 for MMT and DET and 2 for DBT. However derivatization using ethylation provides more reproducible results and is not affected by inorganic interferents.
Tin Spectrophotometry Method comparison Volatile generation Speciation Volatile generation

"Micro-scale Preparation And Characterization Of Isotopically Enriched Monomethylmercury"
Appl. Organomet. Chem. 2002 Volume 16, Issue 10 Pages 610-615
R. C. Rodr&iacute;guez Mart&iacute;n-Doimeadios, T. Stoichev, E. Krupp, D. Amouroux, M. Holeman, O. F. X. Donard

Abstract: A synthesis method for the micro-scale laboratory preparation of isotopically enriched monomethylmercury (MMHg) has been successfully established. This compound is an important standard for species-specific isotope dilution analysis. The isotopically enriched MMHg has been synthesized from commercially available mercury oxide ((HgO)-Hg-201) using methylcobalamin coenzyme as methylating agent. The time required is less than 2 h and the final yield is about 90%. The proposed method is faster than those previously reported in the literature. It allows work on a µscale to control the use of expensive enriched isotope standard. It also allows control of unintentional formation of dimethylmercury. The enriched mercury-containing reaction products were analyzed by capillary gas chromatography coupled to an inductively coupled plasma mass spectrometer after derivatization with sodium tetraethylborate. The isotopic composition, concentration, purity and stability of the synthesized, enriched MMHg have been investigated in order to establish standard protocols for MMHg isotope dilution analysis or isotope labeling incubation experiments.
Synthesis Speciation

"Application Of Isotopically Labeled Methylmercury For Isotope Dilution Analysis Of Biological Samples Using Gas Chromatography/ICPMS"
Anal. Chem. 2002 Volume 74, Issue 11 Pages 2505-2512
R. C. Rodr&iacute;guez Mart&iacute;n-Doimeadios, E. Krupp, D. Amouroux, and O. F. X. Donard

Abstract: An isotope dilution (ID) procedure for the determination of methylmercury (MMHg) in biological samples using an inductively coupled plasma mass spectrometer as detector after the capillary gas chromatographic separation (CGC/ICPMS) has been developed. For the first time, open-focused-microwave pretreatment has been used in conjunction with ID. Optimum conditions for the measurement of isotope ratios on the fast transient chromatographic peaks have been established. Mass bias was found to be about 1.5%/mass unit and was corrected by using the simultaneously measured thallium signals at Tl-203 and Tl-205. After mass-bias correction, deviation of the theoretical mercury ratio values was found to be as low as 0.2%. Isotope ratio precisions based on the peak areas measurements were 0.3% RSD for 20 pg injected (as Hg absolute). The absolute detection limits were in the range of 20-30 fg for Hg-202 and Hg-201. Methylmercury enriched in Hg-201 has been synthesized by direct reaction with methylcobalamine. The concentration of the MMHg spike has been measured by reverse isotope dilution with a natural MMHg standard. The capabilities of CGC/ICPMS to measure isotope ratios were used to optimize sample derivatization by aqueous ethylation with NaBEt4 with respect to MMHg degradation pathways and quantitative recovery. The accuracy of the method developed has been validated with biological certified reference materials (CRM-463, DORM-1).