Arsenic Speciation in Chicken. Mary Carson, Ph.D. FDA/CVM/OR/ Division of Residue Chemistry

Transcription

1 Arsenic Speciation in Chicken Mary Carson, Ph.D. FDA/CVM/R/ Division of Residue Chemistry

2 Elements of Clinical or Public Health Significance

3 Elemental Speciation The chemical species are specific forms of an element defined as to isotopic composition, electronic or oxidation state, and/or complex or molecular structure. The speciation of an element is the distribution of an element amongst defined chemical species in a system. D.M. Templeton, F. Ariese, R. Cornelis, L.-G. Danielsson, H. Muntau, H.P. van Leeuwen, R. Lobinski, IUPAC Guidelines for Terms Related to Speciation of Trace Elements, Pure Appl. Chem., 72/8 (2000) (from

4 Dichotomies Natural vs. Manmade Arsenic is: 1) 20 th most abundant element in the earth s crust 2) Nearly ubiquitous 3) Seldom present as a pure element 4) Present in +3 and +5 valence states 5) The name of the element and the common name of the poison arsenic trioxide 6) Formerly used in insecticides, wood preservatives, etc 7) Used in semi-conductor industry and medicine

5 Dichotomies Natural vs. Manmade rganic vs. Inorganic a (1) : of, relating to, or derived from living organisms (2) : of, relating to, yielding, or involving the use of food produced with the use of feed or fertilizer of plant or animal origin without employment of chemically formulated fertilizers, growth stimulants, antibiotics, or pesticides b (1) : of, relating to, or containing carbon compounds

6 Dichotomies Natural vs. Manmade rganic vs. Inorganic Safe vs. Toxic Arsenobetaine LD 50 ~ 10,000 mg/kg As 2 3 LD 50 ~ 4.5 mg/kg

7 Poison or Not: Depends on SPECIES Lewisite H As - - H As - CH As 3 - H H CH 3 As - tryparsonesyphilis Roxarsone CH 3 CH 3 As CH 3 CH 3 Mel B- sleeping sickness

8 Tools for Speciation Analysis (Microwave-induced plasma) (inductively coupled plasma) (electrospray ionization)

9 ICP-MS Nebulization Desolvation Vaporization Atomization Ionization Mass Analysis liquid aerosol particle molecule atom ion spectrum NEBULIZER SPRAY CHAMBER PLASMA ANALYZER

10 Inductively Coupled Plasma-Mass Spectrometry Benefits Highly sensitive ppt detection limits Huge dynamic range Linear up to10 9 orders of magnitude Compound independent response Versatile Liquid sample introduction Direct elemental analysis Coupled to separation Drawbacks Interferences Identification and quantification errors Isotopic ( 40 Ar vs. 40 Ca) Polyatomic ( 40 Ar 35 Cl vs. 75 As) Matrix effects Quantification errors Nitric acid concentration Carbon concentration No molecular info Expense

11 Total As Determination Microwave nitric acid digestion Dilution Flow injection ICP-MS Yields total amount of As regardless of molecular form Can be used to determine recovery in incurred sample speciation extracts HN 3,

12 Speciation Extraction prefer mild but need efficient Cleanup but not so much that you lose species Separation usually by LC ICP-MS solvent

13 Roxarsone & related cmpds H As - H As - H As - N NH 2 NH H Roxarsone H 3-amino H N-acetyl H As - As - H Arsenate Arsenite H 3 C As - H 3 C As - CH 3 H DMA MMA

14 Ion Chromatography Dionex AS18 column Anion exchanger Low hydrophobicity Hydroxide mobile phase Tetramethyl ammonium hydroxide (TMAH) Step gradient in concentration: 45 mm for 17 min, then 70 mm Alkanol quaternary ammonium group on latex beads

15 Standards chromatogram Abundance As(III) Ion (74.70 to 75.70): 05.D DMA MMA As(V) 3-Amino N-Acetyl Rox Equivalent to 20 ppb in tissue Time-->

16 Sample treatment Weigh 0.5 g Homogenize in 3 ml 0.625% TMAH Dilute to 10 ml Ultrafilter 30K MWC Nearly quantitative recovery in TMAH extracts ~70% recovery through ultrafilters

17 DMA MMA As(III) As(V) 3-Amino N-Acetyl Liver extracts Rox 20 ppb fortified liver Abundance Time--> Treated liver, 0 days withdrawal Time-->

18 As in Chicken: Method Status Comparable results obtained by second lab (FCC) Roxarsone sponsor voluntarily suspended sales in the U.S. Full report available online: mation/ucm htm or and search roxarsone Method manuscript published in 2012 (JAFC 60:9394) Unresolved issues Low mass balance Modify sample prep for muscle ID unknowns

19 Conclusions Ion chromatography-inductively coupled plasma mass spectrometry is useful for speciating arsenic in complex matrices Treating chickens with roxarsone results in liver residue Most of the residue is parent roxarsone Detectable amounts of inorganic As are present

20 Useful links EVISA (Speciation Net) FDA/CFSAN Elemental Analysis Manual mentalanalysismanualeam/default.htm FDA/CVM Roxarsone Study Analyst Report ductsafetyinformation/ucm pdf

21 FDA/CFSAN Acknowledgements Steve Capar, Sean Conklin, Bill Mindak, John Cheng FDA/FCC Doug Heitkemper, Kevin Kubachka, Nohora Shockey FDA/CVM R/DAVR (Joe Kawalek and many others) NADE (many reviewers and statisticians) Phil Kijak, Dave White, Donglei Yu