@article{brecht_kong_shea_xia_nichols_2022, title={Non-target and suspect-screening analyses of hydroponic soybeans and passive samplers exposed to different watershed irrigation sources}, volume={826}, ISSN={["1879-1026"]}, DOI={10.1016/j.scitotenv.2022.153754}, abstractNote={Water scarcity increases the likelihood of irrigating food crops with municipal wastewater that may pose potential dietary risks of regulated and non-regulated organic chemical uptake to edible plant tissues. Only a few studies have used high resolution mass spectrometry (HRMS) to assess the uptake of chemicals of concern into food crops. This study used non-target and suspect-screening analyses to compare total chemical features, tentatively identified chemicals (TICs), and EPA ToxCast chemicals in soybean plants and passive samplers exposed to five different irrigation sources that were collected from an agricultural watershed during mild drought conditions. Secondary-treated municipal wastewater effluent, two surface waters, two ground waters, and deionized municipal tap water were used for two hydroponic experiments: soybean roots and shoots and Composite Integrative Passive Samplers (CIPS) harvested after fourteen days of exposure and soybeans after fifty-six days. CIPS were sealed in separate glass amber jars to evaluate their efficacy to mimic chemical features, TICs, and ToxCast chemical uptake in plant roots, shoots, and beans. Total soybean biomass and water use were greatest for tap water, municipal wastewater, and surface water downstream of the municipal wastewater facility relative to groundwater samples and surface water collected upstream of the wastewater facility. ToxCast chemicals were ubiquitous across watershed irrigation sources in abundance, chemical use category, and number. Wastewater-exposed soybeans had the fewest extractable TICs in plant tissues of all irrigation sources. More ToxCast chemicals were identified in CIPS than extracted from irrigation sources by solid phase extraction. ToxCast chemicals in beans and CIPS were similar in number, chemical use category, and log Kow range. CIPS appear to serve as a useful surrogate for ToxCast chemical uptake in beans, the edible food product.}, journal={SCIENCE OF THE TOTAL ENVIRONMENT}, author={Brecht, Sarah A. and Kong, Xiang and Shea, Damian and Xia, Xin Rui and Nichols, Elizabeth Guthrie}, year={2022}, month={Jun} }
 @article{singh_chao_phillips_xia_shea_sobus_schymanski_ulrich_2020, title={Expanded coverage of non-targeted LC-HRMS using atmospheric pressure chemical ionization: a case study with ENTACT mixtures}, volume={412}, ISSN={["1618-2650"]}, DOI={10.1007/s00216-020-02716-3}, abstractNote={Non-targeted analysis (NTA) is a rapidly evolving analytical technique with numerous opportunities to improve and expand instrumental and data analysis methods. In this work, NTA was performed on eight synthetic mixtures containing 1264 unique chemical substances from the U.S. Environmental Protection Agency’s Non-Targeted Analysis Collaborative Trial (ENTACT). These mixtures were analyzed by atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) using both positive and negative polarities for a total of four modes. Out of the 1264 ENTACT chemical substances, 1116 were detected in at least one ionization mode, 185 chemicals were detected using all four ionization modes, whereas 148 were not detected. Forty-four chemicals were detected only by APCI, and 181 were detected only by ESI. Molecular descriptors and physicochemical properties were used to assess which ionization type was preferred for a given compound. One ToxPrint substructure (naphthalene group) was found to be enriched in compounds only detected using APCI, and eight ToxPrints (e.g., several alcohol moieties) were enriched in compounds only detected using ESI. Examination of physicochemical parameters for ENTACT chemicals suggests that those with higher aqueous solubility preferentially ionized by ESI−. While ESI typically detects a larger number of compounds, APCI offers chromatograms with less background, fewer co-elutions, and additional chemical space coverage, suggesting both should be considered for broader coverage in future NTA research.}, number={20}, journal={ANALYTICAL AND BIOANALYTICAL CHEMISTRY}, author={Singh, Randolph R. and Chao, Alex and Phillips, Katherine A. and Xia, Xin Rui and Shea, Damian and Sobus, Jon R. and Schymanski, Emma L. and Ulrich, Elin M.}, year={2020}, month={Aug}, pages={4931–4939} }
 @article{labens_daniel_hall_xia_schwarz_2017, title={Effect of intra-articular administration of superparamagnetic iron oxide nanoparticles (SPIONs) for MRI assessment of the cartilage barrier in a large animal model}, volume={12}, ISSN={["1932-6203"]}, DOI={10.1371/journal.pone.0190216}, abstractNote={Early diagnosis of cartilage disease at a time when changes are limited to depletion of extracellular matrix components represents an important diagnostic target to reduce patient morbidity. This report is to present proof of concept for nanoparticle dependent cartilage barrier imaging in a large animal model including the use of clinical magnetic resonance imaging (MRI). Conditioned (following matrix depletion) and unconditioned porcine metacarpophalangeal cartilage was evaluated on the basis of fluorophore conjugated 30 nm and 80 nm spherical gold nanoparticle permeation and multiphoton laser scanning and bright field microscopy after autometallographic particle enhancement. Consequently, conditioned and unconditioned joints underwent MRI pre- and post-injection with 12 nm superparamagnetic iron oxide nanoparticles (SPIONs) to evaluate particle permeation in the context of matrix depletion and use of a clinical 1.5 Tesla MRI scanner. To gauge the potential pro-inflammatory effect of intra-articular nanoparticle delivery co-cultures of equine synovium and cartilage tissue were exposed to an escalating dose of SPIONs and IL-6, IL-10, IFN-γ and PGE2 were assessed in culture media. The chemotactic potential of growth media samples was subsequently assessed in transwell migration assays on isolated equine neutrophils. Results demonstrate an increase in MRI signal following conditioning of porcine joints which suggests that nanoparticle dependent compositional cartilage imaging is feasible. Tissue culture and neutrophil migration assays highlight a dose dependent inflammatory response following SPION exposure which at the imaging dose investigated was not different from controls. The preliminary safety and imaging data support the continued investigation of nanoparticle dependent compositional cartilage imaging. To our knowledge, this is the first report in using SPIONs as intra-articular MRI contrast agent for studying cartilage barrier function, which could potentially lead to a new diagnostic technique for early detection of cartilage disease.}, number={12}, journal={PLOS ONE}, author={Labens, Raphael and Daniel, Carole and Hall, Sarah and Xia, Xin-Rui and Schwarz, Tobias}, year={2017}, month={Dec} }
 @article{monteiro-riviere_linder_inman_saathoff_xia_riviere_2012, title={LACK OF HYDROXYLATED FULLERENE TOXICITY AFTER INTRAVENOUS ADMINISTRATION TO FEMALE SPRAGUE-DAWLEY RATS}, volume={75}, ISSN={["1087-2620"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000303594100001&KeyUID=WOS:000303594100001}, DOI={10.1080/15287394.2012.670894}, abstractNote={Hydroxylated fullerenes (C60OHx) or fullerols are water-soluble carbon nanoparticles that have been explored for potential therapeutic applications. This study assesses acute in vivo tolerance in 8-wk-old female Sprague-Dawley rats to intravenous (iv) administration of 10 mg/kg of well-characterized C60(OH)30. Complete histopathology and clinical chemistries are assessed at 8, 24, and 48 h after dosing. Minor histopathology changes are seen, primarily in one animal. No clinically significant chemistry changes were observed after treatment. These experiments suggest that this fullerol was well tolerated after iv administration to rats.}, number={7}, journal={JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH-PART A-CURRENT ISSUES}, author={Monteiro-Riviere, Nancy A. and Linder, Keith E. and Inman, Alfred O. and Saathoff, John G. and Xia, Xin-Rui and Riviere, Jim E.}, year={2012}, pages={367–373} }
 @article{saathoff_inman_xia_riviere_monteiro-riviere_2011, title={In vitro toxicity assessment of three hydroxylated fullerenes in human skin cells}, volume={25}, ISSN={["0887-2333"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000298362500075&KeyUID=WOS:000298362500075}, DOI={10.1016/j.tiv.2011.09.013}, abstractNote={Carbon fullerenes possess unique properties and their interactions with biomolecules have widespread applications. Functionalization of fullerenes with hydroxyl groups (fullerenols) can increase the solubility and potential for cellular interaction, but the health and safety effects of varying degrees of fullerene hydroxylation in biological systems is poorly understood. Existing reports regarding the toxicity and inflammatory potential of fullerenols give conflicting conclusions. To further elucidate the potential for toxicity of fullerenols, human epidermal keratinocytes (HEK) were exposed to fullerenols (low (C60(OH)20), medium (C60(OH)24), and high (C60(OH)32)) at concentrations ranging from 0.000544-42.5 μg/ml for 24 and 48 h. A statistically significant (p<0.05) decrease in viability with alamar Blue (aB) was noted only with C60(OH)32 at 42.5 μg/ml after 24 h. Nanoparticle (NP) controls showed minimal NP/assay interference of the three fullerenols with the aB viability assay. Normalized IL-8 concentration for C60(OH)20 was not significantly different from control, while C60(OH)24 and C60(OH)32 showed a significant decrease at 24 and 48 h. These results suggest that different hydroxylation of fullerenes caused no cytotoxicity or inflammation up to 8.55 μg/ml. These findings suggest that extrapolation across similar NP will be dependent upon surface chemistry and concentration which may affect the degree of agglomeration and thus biological effects.}, number={8}, journal={TOXICOLOGY IN VITRO}, author={Saathoff, J. G. and Inman, A. O. and Xia, X. R. and Riviere, J. E. and Monteiro-Riviere, N. A.}, year={2011}, month={Dec}, pages={2105–2112} }
 @article{xia_monteiro-riviere_mathur_song_xiao_oldenberg_fadeel_riviere_2011, title={Mapping the Surface Adsorption Forces of Nanomaterials in Biological Systems}, volume={5}, ISSN={["1936-086X"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000297143300069&KeyUID=WOS:000297143300069}, DOI={10.1021/nn203303c}, abstractNote={The biological surface adsorption index (BSAI) is a novel approach to characterize surface adsorption energy of nanomaterials that is the primary force behind nanoparticle aggregation, protein corona formation, and other complex interactions of nanomaterials within biological systems. Five quantitative nanodescriptors were obtained to represent the surface adsorption forces (hydrophobicity, hydrogen bond, polarity/polarizability, and lone-pair electrons) of the nanomaterial interaction with biological components. We have mapped the surface adsorption forces over 16 different nanomaterials. When the five-dimensional information of the nanodescriptors was reduced to two dimensions, the 16 nanomaterials were classified into distinct clusters according their surface adsorption properties. BSAI nanodescriptors are intrinsic properties of nanomaterials useful for quantitative structure-activity relationship (QSAR) model development. This is the first success in quantitative characterization of the surface adsorption forces of nanomaterials in biological conditions, which could open a quantitative avenue in predictive nanomedicine development, risk assessment, and safety evaluation of nanomaterials.}, number={11}, journal={ACS NANO}, author={Xia, Xin R. and Monteiro-Riviere, Nancy A. and Mathur, Sanjay and Song, Xuefeng and Xiao, Lisong and Oldenberg, Steven J. and Fadeel, Bengt and Riviere, Jim E.}, year={2011}, month={Nov}, pages={9074–9081} }
 @article{xia_monteiro-riviere_riviere_2010, title={An index for characterization of nanomaterials in biological systems}, volume={5}, ISSN={1748-3387 1748-3395}, url={http://dx.doi.org/10.1038/nnano.2010.164}, DOI={10.1038/nnano.2010.164}, abstractNote={In a physiological environment, nanoparticles selectively absorb proteins to form 'nanoparticle-protein coronas', a process governed by molecular interactions between chemical groups on the nanoparticle surfaces and the amino-acid residues of the proteins. Here, we propose a biological surface adsorption index to characterize these interactions by quantifying the competitive adsorption of a set of small molecule probes onto the nanoparticles. The adsorption properties of nanomaterials are assumed to be governed by Coulomb forces, London dispersion, hydrogen-bond acidity and basicity, polarizability and lone-pair electrons. Adsorption coefficients of the probe compounds were measured and used to create a set of nanodescriptors representing the contributions and relative strengths of each molecular interaction. The method successfully predicted the adsorption of various small molecules onto carbon nanotubes, and the nanodescriptors were also measured for 12 other nanomaterials. The biological surface adsorption index nanodescriptors can be used to develop pharmacokinetic and safety assessment models for nanomaterials.}, number={9}, journal={Nature Nanotechnology}, publisher={Springer Science and Business Media LLC}, author={Xia, Xin-Rui and Monteiro-Riviere, Nancy A. and Riviere, Jim E.}, year={2010}, month={Aug}, pages={671–675} }
 @article{xia_monteiro-riviere_riviere_2010, title={Intrinsic biological property of colloidal fullerene nanoparticles (nC(60)): Lack of lethality after high dose exposure to human epidermal and bacterial cells}, volume={197}, ISSN={["1879-3169"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000280052200010&KeyUID=WOS:000280052200010}, DOI={10.1016/j.toxlet.2010.05.010}, abstractNote={Colloidal fullerene nanoparticles (nC60) were reported to be toxic to fish brains, human cells and microorganisms, while new observations suggest that the observed toxicity may be due to tetrahydrofuran (THF) solvent or its oxidative by-products in nC60 preparations. Here, we report a novel method for preparing nC60 nanoparticles that does not use THF solvent, but provides nC60 with an average particle size of 43.8 nm and a yield approximately 100 times higher than the THF method. The prepared nC60 showed a similar antioxidant capacity compared to a water-soluble vitamin E analog. No mortality to human epidermal keratinocytes was observed at a concentration 170 times higher than the reported LC50 values for other human cell lines. No toxicity was observed to E. coli or B. subtilis at up to 342 microg/mL nC60 for 16 h, which was hundred times higher than the reported minimum inhibitory concentrations of nC60 prepared using THF method for these two bacteria. When E. coli was exposed to 85.5 microg/mL nC60 with daily passage for 4 days, the stationary phase populations at different passages were not statistically different (p = 0.05) from the control without nC60 nanoparticles. These results reveal that the intrinsic biological property of nC60 is non-toxic, confirming the prior non-toxic reports when using nC60 prepared with non-THF methods.}, number={2}, journal={TOXICOLOGY LETTERS}, author={Xia, Xin R. and Monteiro-Riviere, Nancy A. and Riviere, Jim E.}, year={2010}, month={Aug}, pages={128–134} }
 @article{xia_monteiro-riviere_riviere_2010, title={Skin penetration and kinetics of pristine fullerenes (C-60) topically exposed in industrial organic solvents}, volume={242}, ISSN={["1096-0333"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000272434800004&KeyUID=WOS:000272434800004}, DOI={10.1016/j.taap.2009.09.011}, abstractNote={Pristine fullerenes (C60) in different solvents will be used in many industrial and pharmaceutical manufacturing and derivatizing processes. This report explores the impact of solvents on skin penetration of C60 from different types of industrial solvents (toluene, cyclohexane, chloroform and mineral oil). Yorkshire weanling pigs (n = 3) were topically dosed with 500 μL of 200 μg/mL C60 in a given solvent for 24 h and re-dosed daily for 4 days to simulate the worst scenario in occupational exposures. The dose sites were tape-stripped and skin biopsies were taken after 26 tape-strips for quantitative analysis. When dosed in toluene, cyclohexane or chloroform, pristine fullerenes penetrated deeply into the stratum corneum, the primary barrier of skin. More C60 was detected in the stratum corneum when dosed in chloroform compared to toluene or cyclohexane. Fullerenes were not detected in the skin when dosed in mineral oil. This is the first direct evidence of solvent effects on the skin penetration of pristine fullerenes. The penetration of C60 into the stratum corneum was verified using isolated stratum corneum in vitro; the solvent effects on the stratum corneum absorption of C60 were consistent with those observed in vivo. In vitro flow-through diffusion cell experiments were conducted in pig skin and fullerenes were not detected in the receptor solutions by 24 h. The limit of detection was 0.001 μg/mL of fullerenes in 2 mL of the receptor solutions.}, number={1}, journal={TOXICOLOGY AND APPLIED PHARMACOLOGY}, author={Xia, Xin R. and Monteiro-Riviere, Nancy A. and Riviere, Jim E.}, year={2010}, month={Jan}, pages={29–37} }
 @article{baynes_xia_vijay_riviere_2008, title={A solvatochromatic approach to quantifying formulation effects on dermal permeability}, volume={19}, ISSN={["1029-046X"]}, DOI={10.1080/10629360802551026}, abstractNote={Dermal risk assessments are most often concerned with the occupational and environmental exposure to a single chemical and then determining solute permeability through in vitro or in vivo experimentation with various animal models and/or computational approaches. Oftentimes, the skin is exposed to more than one chemical that could potentially modulate dermal permeability of the chemical that could cause adverse health effects. The focus of this article is to demonstrate that these formulation effects on dermal permeability can occur with simple solvent formulations or complex industrial formulations and that these effects can be modeled within the context of a linear solvation energy relationship (LSER). This research demonstrated that formulation-specific strength coefficients (r p a b v) predicted (r 2 = 0.75–0.83) changes in the dermal permeability of phenolic compounds when formulated with commercial metal-working fluid (MWF) formulations or 50% ethanol. Further experimentation demonstrated that chemical-induced changes in skin permeability with 50% ethanol are strongly correlated (r 2 = 0.91) to similar changes in an inert membrane-coated fiber (MCF) array system consisting of three chemically diverse membranes. Changes in specific strength coefficients pertaining to changes in hydrogen donating ability (Δb) and hydrophobicity (Δv) across membrane systems were identified as important quantitative interactions associated with ethanol mixtures. This solvatochromatic approach along with the use of a MCF array system holds promise for predicting dermal permeability of complex chemical formulations in occupational exposures where performance additives can potentially modulate permeability of potential toxicants. †Presented at the 13th International Workshop on QSARs in the Environmental Sciences (QSAR 2008), 8–12 June 2008, Syracuse, USA.}, number={7-8}, journal={SAR AND QSAR IN ENVIRONMENTAL RESEARCH}, author={Baynes, R. E. and Xia, X-R. and Vijay, V. and Riviere, J. E.}, year={2008}, pages={615–630} }
 @article{yeatts_baynes_xia_riviere_2008, title={Application of linear solvation energy relationships to a custom-made polyaniline solid-phase microextraction fiber and three commercial fibers}, volume={1188}, ISSN={["1873-3778"]}, DOI={10.1016/j.chroma.2008.02.057}, abstractNote={The term linear solvation energy relationships, LSERs, is considered to be a specific subset of a larger group of thermodynamic relationships called linear free energy relationships. Overall, the LSERs model represents a three-step thermodynamic process. The most recently accepted notation for the LSER equation, proposed by Abraham is given as follows:SP=c+eE+sS+aA+bB+vVwhere SP is any free energy related property of a solute, such as log K, and each term in the equation represents a specific type of chemical interaction. In this work, LSERs were applied to a custom-made polyaniline (PANI) solid-phase microextraction fiber and three commercial fibers immersed in water in order to aid in the assessment of a diverse series of solutes’ partitioning behavior. By experimentally determining the log K for a series of solutes with known solute descriptors (E, S, A, B, and V) and performing multi-linear regression, the unknown system coefficients (e, s, a, b, and v) were obtained. The sign and magnitude of the system coefficients reflect the relative strengths of chemical interactions that affect partitioning between the two phases (fiber and water). The LSER study showed that the system properties having the greatest influence on log K were ease of cavity formation and hydrogen bond donating ability. The differences in dipolarity/polarizability as well as in hydrogen bond accepting ability further showed that all four fibers offer a unique environment for solute partitioning. The PANI fiber may offer greater flexibility in the choice of fibers to use for solid-phase microextraction.}, number={2}, journal={JOURNAL OF CHROMATOGRAPHY A}, author={Yeatts, James L., Jr. and Baynes, Ronald E. and Xia, Xin-Rui and Riviere, Jim E.}, year={2008}, month={Apr}, pages={108–117} }
 @article{baynes_xia_irman_riviere_2008, title={Quantification of chemical mixture interactions modulating dermal absorption using a multiple membrane fiber array}, volume={21}, ISSN={["1520-5010"]}, DOI={10.1021/tx7002118}, abstractNote={Dermal exposures to chemical mixtures can potentially increase or decrease systemic bioavailability of toxicants in the mixture. Changes in dermal permeability can be attributed to changes in physicochemical interactions between the mixture, the skin, and the solute of interest. These physicochemical interactions can be described as changes in system coefficients associated with molecular descriptors described by Abraham's linear solvation energy relationship (LSER). This study evaluated the effects of chemical mixtures containing either a solvent (ethanol) or a surfactant (sodium lauryl sulfate, SLS) on solute permeability and partitioning by quantifying changes in system coefficients in skin and a three-membrane-coated fiber (MCF) system, respectively. Regression analysis demonstrated that changes in system coefficients in skin were strongly correlated ( R2 = 0.89-0.98) to changes in system coefficients in the three-membrane MCF array with mixtures containing either 1% SLS or 50% ethanol. The PDMS fiber appeared to play a significant role (R2 = 0.84-0.85) in the MCF array in predicting changes in solute permeability, while the WAX fiber appeared to contribute less (R2 = 0.59-0.77) to the array than the other two fibers. On the basis of changes in system coefficients that are part of a LSER, these experiments were able to link physicochemical interactions in the MCF with those interactions in skin when either system is exposed to 1% SLS or 50% ethanol. These experiments further demonstrated the utility of a MCF array to adequately predict changes in dermal permeability when skin is exposed to mixtures containing either a surfactant or a solvent and provide some insight into the nature of the physiochemical interactions that modulate dermal absorptions.}, number={3}, journal={CHEMICAL RESEARCH IN TOXICOLOGY}, author={Baynes, Ronald E. and Xia, Xin Rui and Irman, Mudassar and Riviere, Jim E.}, year={2008}, month={Mar}, pages={591–599} }
 @article{xia_baynes_monteiro-riviere_riviere_2007, title={A system coefficient approach for quantitative assessment of the solvent effects on membrane absorption from chemical mixtures}, volume={18}, ISSN={["1062-936X"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000249294000006&KeyUID=WOS:000249294000006}, DOI={10.1080/10629360701428540}, abstractNote={A system coefficient approach is proposed for quantitative assessment of the solvent effects on membrane absorption from chemical mixtures. The complicated molecular interactions are dissected into basic molecular interaction forces via Abraham's linear solvation energy relationship (LSER). The molecular interaction strengths of a chemical are represented by a set of solute descriptors, while those of a membrane/chemical mixture system are represented by a set of system coefficients. The system coefficients can be determined by using a set of probe compounds with known solute descriptors. Polydimethylsiloxane (PDMS) membrane-coated fibres and 32 probe compounds were used to demonstrate the proposed approach. When a solvent was added into the chemical mixture, the system coefficients were altered and detected by the system coefficient approach. The system coefficients of the PDMS/water system were (0.09, 0.49, −1.11, −2.36, −3.78, 3.50). When 25% ethanol was added into the PDMS/water system, the system coefficients were altered significantly (0.38, 0.41, −1.18, −2.07, −3.40, 2.81); and the solvent effect was quantitatively described by the changes in the system coefficients (0.29, −0.08, −0.07, 0.29, 0.38, −0.69). The LSER model adequately described the experimental data with a correlation coefficient (r 2) of 0.995 and F-value of 1056 with p-value less than 0.0001.}, number={5-6}, journal={SAR AND QSAR IN ENVIRONMENTAL RESEARCH}, author={Xia, X. R. and Baynes, R. E. and Monteiro-Riviere, N. A. and Riviere, J. E.}, year={2007}, pages={579–593} }
 @article{xia_baynes_monteiro-riviere_riviere_2007, title={An experimentally based approach for predicting skin permeability of chemicals and drugs using a membrane-coated fiber array}, volume={221}, ISSN={["1096-0333"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000247278800007&KeyUID=WOS:000247278800007}, DOI={10.1016/j.taap.2007.03.026}, abstractNote={A membrane-coated fiber (MCF) array approach is proposed for predicting the percutaneous absorption of chemicals and drugs from chemical or biological mixtures. Multiple MCFs were used to determine the partition coefficients of compounds (logKMCF). We hypothesized that one MCF will characterize one pattern of molecular interactions and therefore the skin absorption process can be simulated by a multiple MCF array having diverse patterns of molecular interactions. Three MCFs, polydimethylsiloxane (PDMS), polyacrylate (PA) and CarboWax (Wax), were used to determine the logKMCF values for a set of calibration compounds. The skin permeability log(kp) of the compounds was measured by diffusion experiments using porcine skin. The feasibility of the MCF array approach for predicting skin permeability was demonstrated with the three MCFs. A mathematical model was established by multiple linear regression analysis of the log(kp) and logKMCF data set: log(kp) = − 2.34–0.124 logKpdms + 1.91 logKpa − 1.17 logKwax (n = 25, R2 = 0.93). The MCF array approach is an alternative animal model for skin permeability measurement. It is an experimentally based, high throughput approach that provides high prediction confidence and does not require literature data nor molecular structure information in contrast to the existing predictive models.}, number={3}, journal={TOXICOLOGY AND APPLIED PHARMACOLOGY}, author={Xia, Xin-Rui and Baynes, Ronald E. and Monteiro-Riviere, Nancy A. and Riviere, Jim E.}, year={2007}, month={Jun}, pages={320–328} }
 @article{riviere_baynes_xia_2007, title={Membrane-coated fiber array approach for predicting skin permeability of chemical mixtures from different vehicles}, volume={99}, DOI={10.1093/toxsci/kfm155}, abstractNote={A membrane-coated fiber (MCF) array approach was developed for quantitative assessment of skin absorption from chemical mixtures, which was based on the similarity in the absorption mechanisms of the MCF membrane and the stratum corneum of the skin. A set of probe compounds were used to detect the relative molecular interaction strengths of chemicals with the vehicle and the membranes, which provided a linkage between the skin permeability (log k) and MCF partition coefficients (log KF). A predictive model was established via multiple linear regression analysis of the data matrix of experimentally measured log k value and log KFm values; log k=a0+a1 log KF1+a2 log KF2+...+an log KFm, where m is the number of diverse MCFs. Twenty-five probe compounds and three MCFs (polydimethylsiloxane for lipophilic, polyacrylate for polarizable, and CarboWax for polar interactions) were used to demonstrate the model development processes in the MCF array approach. The skin permeability of the probe compounds was measured with conventional diffusion cell experiments using dermatomed porcine skin. Three predictive models were established for skin permeability prediction from chemical mixtures in water, 50% ethanol, and 1% sodium lauryl sulfate (SLS) with R2 values of 93, 91, and 83, respectively. The log k and log KF values were considerably altered by the addition of ethanol or SLS into the dose vehicle; however, their correlations to skin permeability remained strong under various conditions. These results suggested that the experimentally based MCF array approach can be used to predict skin absorption from chemical mixtures in different vehicles or formulations.}, number={1}, journal={Toxicological Sciences}, author={Riviere, J. E. and Baynes, R. E. and Xia, X. R.}, year={2007}, pages={153–161} }
 @article{baynes_xia_barlow_riviere_2007, title={Partitioning behavior of aromatic components in jet fuel into diverse membrane-coated fibers}, volume={70}, ISSN={["1528-7394"]}, DOI={10.1080/15287390701549146}, abstractNote={Jet fuel components are known to partition into skin and produce occupational irritant contact dermatitis (OICD) and potentially adverse systemic effects. The purpose of this study was to determine how jet fuel components partition (1) from solvent mixtures into diverse membrane-coated fibers (MCFs) and (2) from biological media into MCFs to predict tissue distribution. Three diverse MCFs, polydimethylsiloxane (PDMS, lipophilic), polyacrylate (PA, polarizable), and carbowax (CAR, polar), were selected to simulate the physicochemical properties of skin in vivo. Following an appropriate equilibrium time between the MCF and dosing solutions, the MCF was injected directly into a gas chromatograph/mass spectrometer (GC-MS) to quantify the amount that partitioned into the membrane. Three vehicles (water, 50% ethanol–water, and albumin-containing media solution) were studied for selected jet fuel components. The more hydrophobic the component, the greater was the partitioning into the membranes across all MCF types, especially from water. The presence of ethanol as a surrogate solvent resulted in significantly reduced partitioning into the MCFs with discernible differences across the three fibers based on their chemistries. The presence of a plasma substitute (media) also reduced partitioning into the MCF, with the CAR MCF system being better correlated to the predicted partitioning of aromatic components into skin. This study demonstrated that a single or multiple set of MCF fibers may be used as a surrogate for octanol/water systems and skin to assess partitioning behavior of nine aromatic components frequently formulated with jet fuels. These diverse inert fibers were able to assess solute partitioning from a blood substitute such as media into a membrane possessing physicochemical properties similar to human skin. This information may be incorporated into physiologically based pharmacokinetic (PBPK) models to provide a more accurate assessment of tissue dosimetry of related toxicants.}, number={22}, journal={JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH-PART A-CURRENT ISSUES}, author={Baynes, Ronald E. and Xia, Xin-Rui and Barlow, Beth M. and Riviere, Jim E.}, year={2007}, pages={1879–1887} }
 @book{riviere_monteiro-riviere_baynes_xia_2007, title={Quantitating the absorption, partitioning and toxicity of hydrocarbon components of JP-8 jet fuel}, number={FA9550-04-1-0376}, author={Riviere, J. E. and Monteiro-Riviere, N. A. and Baynes, R. E. and Xia, X. R.}, year={2007} }
 @article{kong_shea_baynes_riviere_xia_2007, title={Regression method of the hydrophobicity for determining octanol/water partition ruler approach coefficients of very hydrophobic compounds}, volume={66}, ISSN={["0045-6535"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33751246493&partnerID=MN8TOARS}, DOI={10.1016/j.chemosphere.2006.06.060}, abstractNote={A regression method was developed for the hydrophobicity ruler approach, which is an indirect method for determining the octanol/water partition coefficients of very hydrophobic compounds. Two constants introduced into the mathematical model were obtained by regression of the absorption data sampled before the partition equilibrium. A water miscible organic solvent was used to increase the solubility of the very hydrophobic compounds in the aqueous solution so that the hydrophobicity scale was reduced and the equilibration was accelerated. Polydimethylsiloxane/methanol aqueous solution and a series of 21 polychlorinated biphenyls (PCBs) were used to demonstrate the regression method. The PCB compounds with known experimental logK(o/w) values served as reference compounds, while the PCB compounds without known logK(o/w) values were determined. The distribution coefficients (logK(p/s)), uptake and elimination rate constants were obtained from the two regression constants for each compound (reference or unknown). The correlation of the logK(p/s) values of the reference PCB compounds with their logK(o/w) values was linear (logK(o/w)=2.69logK(p/s)+0.76, R(2)=0.97). The logK(o/w) values were compared with literature values and suggested that some values from the literature far off the calibration line could be inaccurate. The critical experimental factors, the merits of the regression method were discussed.}, number={6}, journal={CHEMOSPHERE}, author={Kong, Xiang Q. and Shea, Damian and Baynes, Ronald E. and Riviere, Jim E. and Xia, Xin-Rui}, year={2007}, month={Jan}, pages={1086–1093} }
 @article{xia_monteiro-riviere_riviere_2006, title={Trace analysis of fullerenes in biological samples by simplified liquid-liquid extraction and high-performance liquid chromatography}, volume={1129}, ISSN={["0021-9673"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000240879200008&KeyUID=WOS:000240879200008}, DOI={10.1016/j.chroma.2006.07.030}, abstractNote={Fullerene (C60) has several potential biomedical and industrial applications. While pure fullerene is not soluble in water, nanoparticles of the fullerene aggregates (nano-C60) can be prepared in water solutions. The concentration of nano-C(60) in biological media after systemic exposure could be very low and requires trace analytical methods to be developed for the toxicological and pharmacokinetic studies of the nanomaterial. A serious drop in extraction efficiency was observed when the concentration was under 0.5 microg/mL using traditional liquid-liquid extraction (LLE) protocols. The evaporation of the solvent extract to dryness was found to be the main reason for the efficiency drop and an improved evaporation method was proposed to overcome this problem. Optimal proportion of glacial acetic acid (GAA) was used to solublize the proteins and surfactants in the biological samples, so that the emulsion problem was eliminated during LLE. Magnesium perchlorate was used to destabilize the nano-C60 particles in the water solution and promoted the solvent extraction. A simplified LLE method was developed for high throughput while preserved the advantages of the traditional LLE. The developed method was used for trace analysis of fullerenes in protein containing media and tape-stripped skin samples. Under optimal experimental conditions, the detection limit was 0.34 ng/mL and the recovery was in the range of 94-100% (n=5) at a concentration of 10 ng/mL nano-C60 in the biological media.}, number={2}, journal={JOURNAL OF CHROMATOGRAPHY A}, author={Xia, Xin-Rui and Monteiro-Riviere, Nancy A. and Riviere, Jim E.}, year={2006}, month={Oct}, pages={216–222} }
 @article{xia_baynes_monteiro-riviere_riviere_2005, title={Determination of the partition coefficients and absorption kinetic parameters of chemicals in a lipophilic membrane/water system by using a membrane-coated fiber technique}, volume={24}, ISSN={["0928-0987"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000226717800002&KeyUID=WOS:000226717800002}, DOI={10.1016/j.ejps.2004.09.004}, abstractNote={The absorption kinetics of chemicals in a lipophilic membrane/water system was studied with a membrane-coated fiber (MCF) technique, in which the partition coefficient, membrane diffusivity and boundary layer adjacent to the membrane were taken into account. The cumulative amount permeated into the membrane was expressed as a function of absorption time in an exponential equation. Two constants were introduced into the model. Both of them were clearly defined by the physiochemical parameters of the system and were obtained by regression of the experimental data sampled over a limited time. The partition and diffusion coefficients, as well as the thickness of the boundary layer, were calculated from the two constants. The kinetic model adequately described the absorption kinetics of the MCF technique. All of the theoretical predictions were supported by the experimental results. The measured partition coefficients correlated well with the published octanol/water partition coefficient (R2 = 0.91). The thickness of the boundary layer was 5.2 μm in a solution stirred at 400 rpm. An inference of the kinetic model revealed that the contribution of the boundary layer to the absorption kinetics is significant for lipophilic chemicals by a lipophilic membrane. It suggested that the absorption rate of a very lipophilic compound could be controlled by the boundary layer even though the diffusivity of the compound in the membrane is lower than that in the solution. It was demonstrated that the MCF technique could be used to determine the partition, diffusion and permeation coefficients, as well as the thickness of the boundary layer in a lipophilic membrane/water system.}, number={1}, journal={EUROPEAN JOURNAL OF PHARMACEUTICAL SCIENCES}, author={Xia, XR and Baynes, RE and Monteiro-Riviere, NA and Riviere, JE}, year={2005}, month={Jan}, pages={15–23} }
 @article{xia_baynes_monteiro-riviere_riviere_2005, title={Membrane uptake kinetics of jet fuel aromatic hydrocarbons from aqueous solutions studied by a membrane-coated fiber technique}, volume={15}, ISSN={["1537-6524"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000230827300008&KeyUID=WOS:000230827300008}, DOI={10.1080/15376520590968888}, abstractNote={The absorption of aromatic hydrocarbons from aqueous media is a critical step involved in many biological processes after occupational and environmental exposures to jet fuel. A membrane-coated fiber (MCF) technique was used to study the uptake kinetics. A flow-through system was used to provide a constant concentration for the prolonged permeation experiments. Polydimethylsiloxane (PDMS) and polyacrylate (PA) MCFs were used to study the differential absorptivity of the aromatic compounds between the two membrane materials. The equilibrium absorption amount and a kinetic parameter describing the absorption kinetics were obtained by the regression of the permeation profiles of the aromatic compounds with a mathematical model. The partition coefficients, uptake, and elimination rate constants were determined for six benzene and three naphthalene derivatives. The PDMS/water partition coefficients of the benzene and naphthalene derivatives were linearly correlated with their logKo/w (LogKpdms/w = 0.871LogKo/w − 0.241, R2 = 0.995). The PA/water partition coefficients of the benzene derivatives and the naphthalene derivatives were correlated differently with their logKo/w. The correlation equations for benzene and naphthalene derivatives were LogKpa/w = 0.865LogKo/w + 0.0045, R2 = 0.997 and LogKpa/w = 0.763LogKo/w + 0.911, R2 = 1.00, respectively. These results suggest that the MCF technique can detect subtle differences in molecular interactions of the two group derivatives between the two membrane/water systems and may be used to study the absorption and permeation properties of closely related compounds. Finally, the regression method is a particularly useful tool to determine partition coefficients of very lipophilic compounds.}, number={4}, journal={TOXICOLOGY MECHANISMS AND METHODS}, author={Xia, XR and Baynes, RE and Monteiro-Riviere, NA and Riviere, JE}, year={2005}, pages={307–316} }
 @article{kong_shea_gebreyes_xia_2005, title={Novel hydrophobicity ruler approach for determining the octanol/water partition coefficients of very hydrophobic compounds via their polymer/solvent solution distribution coefficients}, volume={77}, ISSN={["1520-6882"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-14744281423&partnerID=MN8TOARS}, DOI={10.1021/ac048847r}, abstractNote={A novel hydrophobicity ruler approach for determining the octanol/water partition coefficients of very hydrophobic compounds is proposed, which is an indirect method that measures the polymer/solvent solution distribution coefficients (log Kp/s) of reference and unknown compounds. The log Kp/s values of the unknown compounds can be calibrated to their log Ko/w values via the correlation of the log Kp/s values of the reference compounds with their log Ko/w values. An organic solvent was used to increase the solubility of the very hydrophobic compounds in the aqueous solution, so that their concentrations and absorption amounts were high enough to be measured precisely. The solvent also reduced the hydrophobicity scale of the very hydrophobic compounds and controlled the amounts absorbed into the polymer phase, so that compounds spanning a very wide range of log Ko/w values could be measured in a single measurement and the coexisting compounds would not interfere each other. Poly(dimethylsiloxane) (PDMS), aqueous methanol solutions, and a series of 21 PCB (polychlorinated biphenyl) compounds were used to demonstrate the principle of the hydrophobicity ruler approach. The PCB compounds with known experimental log Ko/w values served as reference compounds, whereas the PCB compounds without known log Ko/w values were determined. The log Ko/w values determined for PCB126, PCB187, PCB197, PCB180, PCB170, and PCB195 were 6.94, 7.84, 8.33, 8.17, 7.92, and 8.49, respectively. The correlation of the log Kp/s values of the reference PCB compounds with their log Ko/w values was linear (log Ko/w=2.56 log Kp/s+1.08, R2=0.95). The hydrophobicity ruler approach is also a valuable tool for validating the experimental and theoretical log Ko/w values and identifying outliers in log Ko/w databases.}, number={5}, journal={ANALYTICAL CHEMISTRY}, author={Kong, XQ and Shea, D and Gebreyes, WA and Xia, XR}, year={2005}, month={Mar}, pages={1275–1281} }
 @article{xia_baynes_monteiro-riviere_riviere_2004, title={A Compartment Model for the Membrane-Coated Fiber Technique Used for Determining the Absorption Parameters of Chemicals into Lipophilic Membranes}, volume={21}, ISSN={0724-8741}, url={http://dx.doi.org/10.1023/b:pham.0000036907.02901.f7}, DOI={10.1023/B:PHAM.0000036907.02901.f7}, abstractNote={{"Label"=>"PURPOSE", "NlmCategory"=>"OBJECTIVE"} The purpose of this work was to develop a compartment model for the membrane-coated fiber (MCF) technique for determining the absorption parameters of chemicals into lipophilic membranes. {"Label"=>"METHODS", "NlmCategory"=>"METHODS"} A polymer membrane coated onto a section of inert fiber was used as a permeation membrane in the MCF technique. When MCFs were immersed into a donor solution, the compounds in the solution partitioned into the membrane. At a given permeation time, a fiber was removed from the solution and transferred into a gas chromatography injector for quantitative analysis. The permeation process of a given chemical from the donor phase into the membrane was described by a one-compartment model by assuming first-order kinetics. {"Label"=>"RESULTS", "NlmCategory"=>"RESULTS"} A mathematical model was obtained that describes the cumulative amount of a chemical permeated into the membrane as a function of the permeation time in an exponential equation. Two constants were introduced into the compartment model that were clearly defined by the physiochemical parameters of the system (a kinetic parameter and the equilibrium absorption amount) and were obtained by regression of the experimental data sampled over a limited time before equilibrium. The model adequately described the permeation kinetics of the MCF technique. All theoretical predictions were supported by the experimental results. The experimental data correlated well with the mathematical regression results. The partition coefficients, initial permeation rate, uptake, and elimination rate constants were calculated from the two constants. {"Label"=>"CONCLUSIONS", "NlmCategory"=>"CONCLUSIONS"} The compartment model can describe the absorption kinetics of the MCF technique. The regression method based on the model is a useful tool for the determination of the partition coefficients of lipophilic compounds when it takes too long for them to reach permeation equilibrium. The kinetic parameter and the initial permeation rate are unique parameters of the MCF technique that could be used in the development of quantitative structure-activity relationship models.}, number={8}, journal={Pharmaceutical Research}, publisher={Springer Science and Business Media LLC}, author={Xia, Xin-Rui and Baynes, Ronald E. and Monteiro-Riviere, Nancy A. and Riviere, Jim E.}, year={2004}, month={Aug}, pages={1345–1352} }
 @article{xia_baynes_monteiro-riviere_riviere_2004, title={Characterization of polyacrylate membrane-coated fibers used in chemical absorption studies with programmed thermal treatment and FT-IR microscopy}, volume={76}, ISSN={["0003-2700"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000222706400053&KeyUID=WOS:000222706400053}, DOI={10.1021/ac0355146}, abstractNote={A polyacrylate (PA) film was coated onto a fused-silica fiber as a permeation membrane in a membrane-coated fiber (MCF) technique and a solid-phase microextraction technique. The molecular changes of the PA membrane after different temperature treatments were studied with FT-IR microscopy. The absorption bands of the PA aliphatic backbone at 2902, 2795, and 2740 cm(-)(1) remained unchanged over the elevated thermal treatments, indicating that the polymer backbone was stable over these conditions. The spectra of the PA membrane remained unchanged when the thermal treatment temperature was under 150 degrees C. When the temperature was 250 degrees C, the O-H stretching band in the -COOH groups of the poly(acrylic acid) at 3315 cm(-)(1) was significantly reduced. When the temperature was higher than 280 degrees C, this O-H band disappeared. These evidences suggested that the PA membrane underwent dehydroxyl reaction to form an anhydride when the thermal treatments were higher than 250 degrees C. Thermal treatments of a deuterated PA MCF confirmed the anhydride formation mechanism. The anhydride formation explained the absorption property of PA MCFs in GC applications where they must be preconditioned at 300 degrees C. The absorption data suggest that a PA fiber does not preferably absorb polar compounds (with permanent dipole moment); instead, it absorbs preferably aromatic compounds.}, number={14}, journal={ANALYTICAL CHEMISTRY}, author={Xia, XR and Baynes, RE and Monteiro-Riviere, NA and Riviere, JE}, year={2004}, month={Jul}, pages={4245–4250} }
 @article{muhammad_baynes_monteiro-riviere_xia_riviere_2004, title={Dose related absorption of JP-8 jet fuel hydrocarbons through porcine skin with quantitative structure permeability relationship analysis}, volume={14}, ISSN={["1537-6524"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000220690300003&KeyUID=WOS:000220690300003}, DOI={10.1080/15376520490429319}, abstractNote={The effects of dosage on the percutaneous absorption of jet fuel hydrocarbons is not clear, yet is essential for human risk assessment. The present study is an ongoing approach to assess the dose-related percutaneous absorption of a number of aliphatic and aromatic hydrocarbons. The first treatment (1X) was comprised of mixtures containing undecane (4.1%), dodecane (4.7%), tridecane (4.4%), tetradecane (3%), pentadecane (1.6%), naphthalene (1.1%), and dimethyl naphthalene (1.3% of jet fuels) in hexadecane solvent using porcine skin flow through diffusion cell. Other treatments (n = 4 cells) were 2X and 5X concentrations. Perfusate samples were analyzed with gas chromatography-flame ionization detector (GC-FID) using head space solid phase micro-extraction fiber technique. We have standardized the assay to have a good linear correlation for all the tested components in media standards. Absorption parameters including diffusivity, permeability, steady state flux, and percent dose absorbed were estimated for all the tested hydrocarbons. This approach provides a baseline to access component interactions among themselves and with the diluent (solvents). A quantitative structure permeability relationship (QSPR) model was derived to predict the permeability of unknown jet fuel hydrocarbons in this solvent system by using their physicochemical parameters. Our findings suggested a dose related increase in absorption for naphthalene and dimethyl naphthalene (DMN).}, number={3}, journal={TOXICOLOGY MECHANISMS AND METHODS}, author={Muhammad, F and Baynes, RE and Monteiro-Riviere, NA and Xia, XR and Riviere, JE}, year={2004}, pages={159–166} }
 @article{xia_baynes_monteiro-riviere_leidy_shea_riviere_2003, title={A novel in-vitro technique for studying percutaneous permeation with a membrane-coated fiber and gas chromatography/mass spectrometry: Part I. Performances of the technique and determination of the permeation rates and partition coefficients of chemical mixtures}, volume={20}, ISSN={["0724-8741"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0037331884&partnerID=MN8TOARS}, DOI={10.1023/A:1022287524024}, abstractNote={{"Label"=>"PURPOSE", "NlmCategory"=>"OBJECTIVE"} To develop a novel in-vitro technique for rapid assessment of percutaneous absorption of chemical mixtures. {"Label"=>"METHODS", "NlmCategory"=>"METHODS"} A silastic membrane was coated on to a fiber to be used as a permeation membrane. The membrane-coated fiber was immersed in the donor phase to partition the compounds into the membrane. At a given partition time, the membrane-coated fiber was transferred into a GC injector to evaporate the partitioned compounds for quantitative and qualitative analyses. {"Label"=>"RESULTS", "NlmCategory"=>"RESULTS"} This technique was developed and demonstrated to study the percutaneous permeation of a complex mixture consisting of 30 compounds. Each compound permeated into the membrane was identified and quantified with GC/MS. The standard deviation was less than 10% in 12 repeated permeation experiments. The partition coefficients and permeation rates in static and stirred donor solution were obtained for each compound. The partition coefficients measured by this technique were well correlated (R2 = 0.93) with the reported octanol/water partition coefficients. {"Label"=>"CONCLUSIONS", "NlmCategory"=>"CONCLUSIONS"} This technique can be used to study the percutaneous permeation of chemical mixtures. No expensive radiolabeled chemicals are required. Each compound permeated into the membrane can be identified and quantified. The initial permeation rate and equilibrium time can be obtained for each compound, which could serve as characteristic parameters regarding the skin permeability of the compound.}, number={2}, journal={PHARMACEUTICAL RESEARCH}, author={Xia, XR and Baynes, RE and Monteiro-Riviere, NA and Leidy, RB and Shea, D and Riviere, JE}, year={2003}, month={Feb}, pages={275–282} }
 @article{xia_leidy_2002, title={A simplified liquid-solid extraction technique for the analyses of pesticide residues in soil samples}, volume={73}, ISSN={["0167-6369"]}, DOI={10.1023/A:1013017804165}, abstractNote={A simplified liquid-solid extraction technique was studied for the analyses of pesticide residues in soil samples. It is a simple, one step sample preparation method based on a relative quantification concept. Linear response curves were obtained for all of the target compounds regardless of their surface adsorption. This observation was explained and modeled to obey Langmuir adsorption Equation. The adsorption of analytes onto the sample surfaces will sacrifice the detection sensitivity. The strategies to reduce the surface adsorption, such as, molecular replacement and selection of solvents, were discussed. The relative quantification and the wide varieties of available solvents would enable the technique to be a useful method for the monitoring and analyses of pesticide residues in soils.}, number={2}, journal={ENVIRONMENTAL MONITORING AND ASSESSMENT}, author={Xia, XR and Leidy, RB}, year={2002}, month={Jan}, pages={179–190} }
 @article{xia_leidy_2001, title={Preparation and characterization of porous silica coated multifibers for solid-phase microextraction}, volume={73}, ISSN={["0003-2700"]}, DOI={10.1021/ac001273f}, abstractNote={C18-bonded silica-coated multifibers were prepared and studied as a stationary phase for solid-phase microextraction (SPME). The porous multifiber SPME provided larger absorption capacity and higher absorption rate compared to a polymer-coated single fiber. Its absorption rate was 10 times higher than that of a commercial 100-microm poly(dimethylsiloxane) (PDMS)-coated fiber. Its high extraction efficiency enabled the positive identification of unknown compounds at sub-part-per-billion level in full-scan mode with a benchtop quadruple GC/MS. The desorption temperature indicated that the analyte interactions with the C18-bonded silica were stronger than those with the PDMS polymer. The dependence of the equilibration time on the molecular weight was not observed for the porous multifiber SPME. The boundary layer between the fiber coating and the sample matrix could be the absorption control step in SPME under mild agitation. The special experimental conditions in the porous multifiber SPME, such as air interference and polar organic solvent wetting, were investigated.}, number={9}, journal={ANALYTICAL CHEMISTRY}, author={Xia, XR and Leidy, RB}, year={2001}, month={May}, pages={2041–2047} }
 @inbook{xia_baynes_riviere, title={A novel system coefficient approach for systematic assessment of dermal absorption from chemical mixtures}, ISBN={0415700361}, booktitle={Dermal absorption models in toxicology and pharmacology}, publisher={New York: Taylor and Francis / CRC Press}, author={Xia, X. R. and Baynes, R. E. and Riviere, J. E.}, pages={69–86} }
 @misc{riviere_xia_baynes_monteiro-riviere, title={Method and apparatus for determining a molecular descriptor of absorption for a candidate compound}, volume={7,517,693}, number={2009 Apr. 14}, author={Riviere, J. E. and Xia, X. R. and Baynes, R. E. and Monteiro-Riviere, N. A.} }
 @book{riviere_montiero-riviere_baynes_xia_smith, title={Quantitating the percutaneous absorption of mechanistically-defined chemical mixtures}, volume={34}, author={Riviere, J. E. and Montiero-Riviere, N. A. and Baynes, R. E. and Xia, X. R. and Smith, C. E.}, pages={1} }