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Wolle M.M.,Duquesne University | Rahman G.M.M.,Applied Isotope Technologies Inc. | Skip Kingston H.M.,Duquesne University | Pamuku M.,Applied Isotope Technologies Inc.
Journal of Analytical Atomic Spectrometry | Year: 2014

Strategies were designed to quantify hexavalent (Cr(vi)), soluble trivalent (Cr(iii)) and insoluble chromium (Cr) species in soil by integrating existing methods of Cr(vi) and total Cr determination with speciated isotope dilution mass spectrometry (SIDMS, EPA Method 6800). Two different extraction methods that utilize a NaOH-Na2CO3 solution (EPA Method 3060A) and alkaline solution of ethylenediaminetetraacetic acid (EDTA) were used to extract Cr(vi) (along with soluble Cr(iii) in the latter case). The extracted Cr was speciated by ion chromatography-inductively coupled plasma mass spectrometry (IC-ICP-MS), and the separated species were quantified using the mathematical relationships in SIDMS with simultaneous correction for their method-induced transformations. The Cr species that fell out as insoluble solid during extraction were determined by isotope dilution mass spectrometry (IDMS) after decomposing the extraction residues in a mixture of mineral acids according to EPA Method 3052. Several certified reference materials and a soil sample were analyzed using the proposed strategies. The measured mass fractions of Cr(vi) and total Cr in the reference materials statistically agreed with the certified values at 95% CL. The insoluble fraction of Cr accounted for 64-107% of the total Cr in the samples. The validity of the strategies was proved using mass balance by comparing the sum of the mass fractions of Cr(vi), soluble Cr(iii) and insoluble Cr with the total Cr measured in the corresponding samples; the latter was determined by IDMS after decomposing the soils using EPA Method 3052 with single spiking. This journal is © the Partner Organisations 2014.


Wolle M.M.,Duquesne University | Fahrenholz T.,Applied Isotope Technologies Inc. | Rahman G.M.M.,Applied Isotope Technologies Inc. | Pamuku M.,Applied Isotope Technologies Inc. | And 2 more authors.
Journal of Chromatography A | Year: 2014

An ion chromatography-inductively coupled plasma mass spectrometry (IC-ICP-MS) method was developed for the redox speciation analysis of iron (Fe) based on in-column complexation of Fe2+ and Fe3+ by dipicolinic acid (DPA). The effects of column type, mobile phase composition and molecular ion interference were studied in the method optimization. The carryover of the target species in the IC-ICP-MS method was uniquely and effectively evaluated using isotopically enriched analogues of the analytes (54Fe2+ and 57Fe3+). Standard solutions of the enriched standards were injected into the system following analysis of a sample, and the ratios of the isotopes of iron in the enriched standards were calculated based on the chromatographic peak areas. The concentrations of the analytes carried over from the sample to the enriched standards were determined using the quantitative relationship in isotope dilution mass spectrometry (IDMS). In contrast to the routine way of evaluating carryover effect by injecting a blank solution after sample analysis, the use of isotopically enriched standards identified significant analyte carryover in the present method. Extensive experiments were carried out to systematically identify the source of the carryover and to eliminate the problem; the separation column was found to be the exclusive source. More than 95% of the analyte carryover was eliminated by reducing the length of the column. The detection limit of the IC-ICP-MS method (MDL) for the iron species was 2ngg-1. The method was used to determine Fe2+ and Fe3+ in synthetic aqueous standard solutions and a beverage sample. © 2014 Elsevier B.V.


Boggess A.J.,Duquesne University | Rahman G.M.M.,Applied Isotope Technologies Inc. | Pamukcu M.,Applied Isotope Technologies Inc. | Faber S.,The Childrens Institute of Pittsburgh | Kingston H.M.S.,Duquesne University
Analyst | Year: 2014

A robust method has been developed for easy transfer between analytical laboratories to obtain highly accurate and reproducible quantification of persistent organic pollutants (POPs) in micro-volumes of serum. This method is suited for analysts researching the impact of environmental exposure on human health. When performed by highly trained analysts, existing methods can produce high quality data; however, complex sample preparation steps often cannot be consistently replicated by laboratories, leading to variance in extraction recovery and quantitation. By combining stir-bar sorptive extraction (SBSE) with direct isotope dilution (D-ID) mass spectrometry quantification, a new analytical method was developed. The D-ID quantification significantly improved accuracy, corrected sample-to-sample irreproducibility, and reduced sample preparation time. Independent production of statistically identical data then confirmed transfer of the validated operating protocol to an off-site laboratory with different instrument models. SBSE performance was compared with industry-accepted extraction techniques. D-ID quantification was compared with peer-reviewed relative isotopic response factor (RF) quantification methods. Holding other variables constant, D-ID improved accuracy by 250% and precision by 300% compared with RF; SBSE improved accuracy by 37% compared to industry-accepted extraction methods. Limits of quantification of the analytes ranged from 60 pg g-1 to 1 μg g-1. Protocol transfer exhibited <7% mean between-laboratory error and <2% mean within-laboratory RSD. These results indicate that a transferable method has been developed for academic, government, commercial, and clinical laboratories seeking to maximize throughput and improve quantitative validity. This validated method was applied in a recent clinical study to assess non-communicable disease in children in Pennsylvania, USA. This journal is © the Partner Organisations 2014.


Wolle M.M.,Duquesne University | Rahman G.M.M.,Applied Isotope Technologies Inc. | 'Skip' Kingston H.M.,Duquesne University | Pamuku M.,Applied Isotope Technologies Inc.
Analytica Chimica Acta | Year: 2014

A study was conducted to develop a microwave-enhanced extraction method for the determination of arsenic species in prenatal and children's dietary supplements prepared from plant materials. The method was optimized by evaluating the efficiency of various solutions previously used to extract arsenic from the types of plant materials used in the dietary supplement formulations. A multivitamin standard reference material (NIST SRM 3280) and a prenatal supplement sample were analyzed in the method optimization. The identified optimum conditions were 0.25g of sample, 5mL of 0.3molL-1 orthophosphoric acid (H3PO4) and microwave heating at 90°C for 30min. The extracted arsenic was speciated by cation exchange ion chromatography-inductively coupled plasma mass spectrometry (IC-ICP-MS). The method detection limit (MDL) for the arsenic species was in the range 2-8ngg-1. Ten widely consumed prenatal and children's dietary supplements were analyzed using the optimized protocol. The supplements were found to have total arsenic in the concentration range 59-531ngg-1. The extraction procedure recovered 61-92% of the arsenic from the supplements. All the supplementary products were found to contain arsenite (As3+) and dimethylarsinic acid (DMA). Arsenate (As5+) was found in two of the supplements, and an unknown specie of arsenic was detected in one product. The results of the analysis were validated using mass balance by comparing the sum of the extracted and non-extracted arsenic with the total concentration of the element in the corresponding samples. © 2014 Elsevier B.V.


Rahman G.M.M.,Applied Isotope Technologies Inc. | Wolle M.M.,Duquesne University | Fahrenholz T.,Applied Isotope Technologies Inc. | Kingston H.M.S.,Duquesne University | Pamuku M.,Applied Isotope Technologies Inc.
Analytical Chemistry | Year: 2014

A biomonitoring method was developed for the determination of inorganic-, methyl-, and ethylmercury (Hg2+, CH3Hg+, and C2H5Hg+, respectively) in whole blood by triple-spiking speciated isotope dilution mass spectrometry (SIDMS) using headspace (HS) solid-phase microextraction (SPME) in combination with gas chromatographic (GC) separation and inductively coupled plasma mass spectrometric (ICP-MS) detection. After spiking the blood sample with isotopically enriched analogues of the analytes (199Hg2+, CH3 200Hg+ and C2H5 201Hg+), the endogenous Hg species were solubilized in 2.0 mol L-1 HNO3 and equilibrated with the spikes using a microwave-enhanced protocol. The microwaved sample was treated with a 1% (w/v) aqueous solution of sodium tetrapropylborate (buffered to pH 5.2), and the propylated Hg species were sampled in the HS using a Carboxen/ polydimethylsiloxane-coated SPME fiber. The extracted species were thermally desorbed from the fiber in the GC injection port and determined by GC-ICP-MS. The analytes were quantified, with simultaneous correction for their method-induced transformation, on the basis of the mathematical relationship in triple-spiking SIDMS. The method was validated using a bovine blood standard reference material (SRM 966, Level 2). Analysis of human blood samples demonstrated the accuracy and reproducibility of the method, which can detect the Hg species down to 30 pg g-1 in blood. The validity of the analytical results found for the blood samples was demonstrated using mass balance by comparing the sum of the concentrations of the individual Hg species with the total Hg in the corresponding samples; the latter was determined by isotope dilution mass spectrometry (IDMS) after decomposing the blood using EPA Method 3052 with single-spiking. © 2014 American Chemical Society.


Martone N.,Duquesne University | Rahman G.M.M.,Applied Isotope Technologies Inc. | Pamuku M.,Applied Isotope Technologies Inc. | Kingston H.M.S.,Duquesne University
Journal of Agricultural and Food Chemistry | Year: 2013

In order to determine the health impact of chromium in dietary supplements, the Cr(III) and Cr(VI) must be independently measured and verified with mass balance (sum of both species equaling independent measurements of total chromium), as both may be present in finished products. Because Cr(III) is stable in acidic conditions and Cr(VI) in alkaline conditions, interconversions between species may occur in complex matrices and during analytical extraction, increasing the difficulty of quantification. A study was conducted to determine Cr(VI) and Cr(III) in dietary supplements. EPA Method 3060A extraction protocol was performed to extract Cr(VI), and EPA Method 3052 was performed on the extracted residue to digest the remaining Cr(III). Speciated isotope dilution mass spectrometry (SIDMS), as described in the EPA Method 6800 (update V), was implemented with ion-exchange chromatography inductively coupled plasma mass spectrometry (IC-ICP-MS). Method 6800 uniquely enables tracking and correcting for the bidirectional chromium interspecies conversions that occur during extraction and sample handling prior to instrumental analysis. Mass balance results indicated that the off-the-shelf dietary supplements analyzed during this study contained hexavalent chromium ranging from


PubMed | Johns Hopkins University, Duquesne University, Air Force Medical Support Agency, Applied Isotope Technologies Inc. and The Center for Resources in Integrative Biology
Type: Journal Article | Journal: Military medicine | Year: 2015

Systems biology (omics) technologies are emerging as tools for the comprehensive analysis and monitoring of human health. In order for these tools to be used in military medicine, clinical sampling and biobanking will need to be optimized to be compatible with downstream processing and analysis for each class of molecule measured. This article provides an overview of omics technologies, including instrumentation, tools, and methods, and their potential application for warfighter exposure monitoring. We discuss the current state and the potential utility of personalized data from a variety of omics sources including genomics, epigenomics, transcriptomics, metabolomics, proteomics, lipidomics, and efforts to combine their use. Issues in the sample-to-answer workflow, including collection and biobanking are discussed, as well as national efforts for standardization and clinical interpretation. Establishment of these emerging capabilities, along with accurate xenobiotic monitoring, for the Department of Defense could provide new and effective tools for environmental health monitoring at all duty stations, including deployed locations.


PubMed | Environment Canada, Applied Isotope Technologies Inc. and Duquesne University
Type: | Journal: Talanta | Year: 2016

The reliable analysis of highly toxic hexavalent chromium, Cr(VI), at ultra-trace levels remains challenging, given its easy conversion to non-toxic trivalent chromium. This work demonstrates a novel analytical method to quantify Cr(VI) at low ngL(-1) concentration levels in environmental water samples by using speciated isotope dilution (SID) analysis and double-spiking with Cr(III) and Cr(VI) enriched for different isotopes. Ion chromatography tandem mass spectrometry (IC-MS/MS) was used for the analysis of Cr(VI) as HCrO4(-) CrO3(-). Whereas the classical linear multipoint calibration (MPC) curve approach obtained a method detection limit (MDL) of 7ngL(-1) Cr(VI), the modified SID-MS method adapted from U. S. EPA 6800 allowed for the quantification of Cr(VI) with an MDL of 2ngL(-1) and provided results corrected for Cr(VI) loss occurred after sample collection. The adapted SID-MS approach proved to yield more accurate and precise results than the MPC method, allowed for compensation of Cr(VI) reduction during sample transportation and storage while eliminating the need for frequent external calibration. The developed method is a complementary tool to routinely used inductively-coupled plasma (ICP) MS and circumvents typically experienced interferences.


Trademark
Applied Isotope Technologies Inc. | Date: 2013-05-29

Medical diagnostic reagents and assays for testing of body fluids.

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