Introduction Ghent University Arsenic Speciation Inorganic - PDF document

2/24/2011 Faculty of Bioscience Engineering Department of Applied Analytical and Physical Chemistry Ghent University Laboratory of Analytical Chemistry and Applied Ecochemistry Arsenic and Arsenic Speciation Pradeep Alava Promoter: Filip Tack, Tom van de Wiele Co-Promoter: Gijs Du Laing Contact mail: Pradeep.alava@UGent.be Introduction Ghent University Arsenic = Toxic Regulatory limits � EPA – RfD - 0.3 µg/kg/day � ATSDR – MRL – 0.3 µg/kg/day (chronic exposure) � WHO – 10 µg/l drinking water � OSHA – Workplace air 0.5 mg/m 3 1

2/24/2011 Introduction Ghent University Arsenic Speciation Inorganic • Pentavalent (AsV) • Trivalent (As III) Organic Methylated • Pentavalent (DMA V, MMA V etc) • Trivalent (DMA III, MMAIII) Thiolated (MMTA, DMDTA etc) • Inorganic forms are more toxic than pentavalent methylated species • Trivalent methylated species are more toxic than inorganic species • Speciation studies are very important to assess the toxicity. Objective Ghent University To assess the physical, chemical and microbial effect on biotransformation of As species in human gastrointestinal tract. Development of a analytical method to identify and quantify different As species. Incubation experiments using SHIME, where we can mimic human gut environment to study microbial affect. Assess the Physical and chemical factors effecting biotransformation of arsenic species 2

2/24/2011 Method Development Ghent University Method Development Ghent University 3

2/24/2011 Incubation Experiment ( SHIME) Ghent University • mimicks physicochemical, enzymatic and microbiological processes of the human intestine • validated against in vivo data concerning – microbial community composition – microorganism-associated enzymatic activities • long-term-stability of the microbial community composition stomach Molly et al. (1993) Appl Microbiol Biotechnol, 39, 254-258. small Molly et al. (1994) Microbial Ecol Health Disease, 7 , stomach intestine colon 191-200 ascendending transverse Possiemiers et al. (2004) Fems Microbiol Ecol, 49, descendending 495-507 Sample Preparation Ghent University 0.5g sample 0.5g sample Incubated sample 50 mL polypropylene 50 mL polypropylene Centrifuged tubes tubes Supernatant and pellet 10 ml MilliQ water 10 ml MilliQ water collected Microwave Digestion Microwave Digestion Freeze At 80 o C At 80 o C Thawed before analysis Made up to 25 mL Speciation Analysis Total analysis on pellet, Total Analysis Speciation analysis on supernatant 4

2/24/2011 Analytical Setup Ghent University Detector Torch Mass analyzer Nebulizer Total Analysis of Arsenic Analytical Setup Ghent University ICP torch Q-pole mass filter nebulizer & spray chamber turbo turbo molecular molecular pump pump rotary pump gas controller Ar gas liquid chromatograph Speciation Analysis of Arsenic 5

2/24/2011 Results Ghent University Results Ghent University 6

2/24/2011 Results Ghent University • HPLC-ICP-MS hyphenated method developed to identify and quantify seven different arsenic species. • Biotransformation to trivalent methylated species and thiolated species took place after incubating rice samples in SHIME. • No thiolation or methylation obesrved in autoclaved SHIME incubations. Conclusions Ghent University • Currently able to detect and quantify total amount of arsenic and different arsenic species even at non equimolar ratios in water, environment samples, food samples etc. • Future perspective : Assessment of Physical and chemical factors affecting transformation of As species within the gastrointestinal tract. 7

2/24/2011 Ghent University 8

Introduction Ghent University Arsenic Speciation Inorganic - PDF document

2/24/2011 Faculty of Bioscience Engineering Department of Applied Analytical and Physical Chemistry Ghent University Laboratory of Analytical Chemistry and Applied Ecochemistry Arsenic and Arsenic Speciation Pradeep Alava Promoter: Filip

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