Differentiation Between Nutritional and Carcinogenic ...€¦ · Differentiation Between...
Transcript of Differentiation Between Nutritional and Carcinogenic ...€¦ · Differentiation Between...
www.brooksapplied.com
Differentiation Between Nutritional and Carcinogenic Selenium via Speciation AnalysesRussell GeradsBusiness Development DirectorBrooks Applied Labs
Presented at the AOAC Conference, September 29, 2015
Presentation Outline:
I thought selenium was a nutrient…Selenium sourcesApplied Analytical MethodsAnalytical FindingsImplications for Humans, Cattle, Fish, and the Ecosystem
I Thought Selenium was a Nutrient…
Selenium is an essential trace element
Deficiency is widespread and causes increased cancer ratesEfforts to enrich nutrition in Se are underway in many areas
Reduces certain types of cancer (antioxidant in the form of glutathione peroxidase)
Reduces As toxicity (Se-As complexes)
Reduces Hg bioaccumulation (Se-Hg complexes)
I Thought Selenium was a Nutrient…
Se biomagnifies (review in a few minutes)
Effects observed:TeratogenicityMutagenDecreases reproductive efficiencyCirrhosis of the liver
Most organic-Se compounds are readily absorbed (increased uptake), but inorganic Se species dominate in the environment; somewhere along the process, conversion of inorganic Se into organic Se species must occur (rate limiting step)Selenate mobilized through sulfate chemical pathways for plants (greater efficiency than selenite)
I Thought Selenium was a Nutrient…
I Thought Selenium was a Nutrient…
I Thought Selenium was a Nutrient…
Biochemical Implications
Sulfur and oxygen analogues
Volatile methylated compounds(CH3-Se-CH3, CH3-Se-Se-CH3, CH3-SeO2-CH3)
Se-amino acids and Se proteinsSelenoamino acids (sulfur analogues)SelenomethionineSelenocysteineOther…
Biochemical Implications
Which Selenium is Nutritional?
Which Selenium is Nutritional?
Source: Rigby, M., Gerads, R., Lemly, D. Environmental Science Process & Impacts 2014
Selenium SourcesElectronics (diodes, photoelements, rectifiers, LEDs)Vulcanizing agent for rubberMedicine / nutritional supplementVegetation, groundwater, feed, food additives (human too!)Coal combustion (fly ash)Flue gas desulphurization (FGD)Oil refiningManufacturing gas plantsCoal and phosphorus miningRunoff from agricultural irrigation in arid regionsSe is produced from anodic sludge in copper refining andfrom lead chamber sludge in sulfuric acid production
Selenium Sources
Selenium production from copper mines and anode mud from electrolytic Cu refineries:
Cu2Se + Na2CO3 + 2O2 2CuO + Na2SeO3 + CO2
Acidified with sulfuric acid forming H2SeO3
H2SeO3 + 2SO2 + H2O Se(s) + 2H2SO4
Applied Analytical Methods
Size exclusion inductively coupled plasma dynamic reaction cell mass spectrometry (SEC-ICP-DRC-MS) – Selenoproteins and selenoaminoacids
Ion chromatography inductively coupled plasma dynamic reaction cell mass spectrometry (IC-ICP-DRC-MS) – Se(IV), Se(VI), SeCN, MeSe(IV)
Reverse phase chromatography inductively coupled plasma dynamic reaction cell mass spectrometry (RP-ICP-DRC-MS) – Seleno-amino acids and other small molecular metabolites
Extraction for selenoamino acids must be specific to intent: seleno-amino acids versus selenoproteins
Different selenoamino acids and proteins applied to inorganic selenium extraction method to confirm molecular degradation did not transpire
Applied Analytical Methods
Many published methods use or reference EXAFS/XANES
Problem:Utility of method limited to adjacent atoms
Many gross assumptions made regarding molecular forms using x-ray spectrometry
For more information please read:
Rigby, M., Lemly, D., Gerads, R. “Fish toxicity testing with selenomethionine spiked feed – what's the real question being asked?” Environmental Sci.: Processes & Impact. 2014, 16, 511.
Selenium Speciation Analysis by SEC-ICP-MS
Computer Waste
Column Oven
ICP-MS
AutosamplerLC Pump
A B
Column
Selenium Speciation Analysis by SEC-ICP-MS
Size exclusion inductively coupled plasma mass spectrometry (SEC-ICP-MS) – Selenoproteins and selenoamino acids
Flow
Large moleculesSmall molecules
Molecular identification by retention times for known standards (macro molecules require monitoring for other elements)
Selenium Speciation Analysis by SEC-ICP-MS
SeCN
Se-amino
Se(IV)
SeP
Selenium Speciation Analysis by IC-ICP-MS
Ion chromatography inductively coupled plasma dynamic reaction cell mass spectrometry (IC-ICP-DRC-MS) – Se(IV), Se(VI), SeCN, MeSe(IV)
Flow
Large moleculesSmall molecules separated by ionic interactions
Molecular identification by retention times for known standards
Selenium Speciation Analysis by IC-ICP-MS
Selenium Speciation Analysis by RP-ICP-MS
Reverse phase chromatography inductively coupled plasma mass spectrometry (RP-ICP-DRC-MS) – Se(IV), Se(VI), selenomethionine, selenocysteine, methylselenocystein, other seleno-amino acids
Flow
Large moleculesSmall molecules separated by carbon and ionic interactions
Molecular identification by retention times for known standards
Selenium Speciation Analysis by IC-ICP-MS
Full Time Range EIC(78) : 017SMPL_130827-ICPMS7-IC-SeMet-2_130827-ICPMS7-IC-SeMet Crunch.D
RT(min)
4.0 8.0 12.0Count
3x10
0
1
2
nd Name=O-setmet Exp. RT=2.89312 Det. RT=2.91960 Area=6407 Height=366
Compound Name=SetMet Exp. RT=5.69687 Det. RT=5.76248 Area=595259 Height=31104
Compound Name=Se4 Exp. RT=7.78530 Det. RT=7.78530 Area=11892 Height=1604
Enzymatically extracted yeast sample analyzed by RP-ICP-MS
>85% SeMe
Selenium Speciation Analysis by IC-ICP-MS
Full Time Range EIC(78) : 085SMPL_140414-SeMet.D
RT(min)
4.0 8.0 12.0
Count
2x10
0
2
4
Compound Name=SeMet Exp. RT=3.347 Det. RT=3.347 Area=49 Height=13
Compound Name=Se4 Exp. RT=4.328 Det. RT=4.047 Area=229947 Height=31053 Enzymatically extracted yeast sample analyzed by RP-ICP-MS
>90% Se(IV)
Implications for Humans, Cattle, Fish, and the Ecosystem
Toxicological risk dictated by organism
Not all food additives are the same “Selenized yeast”
Risk concerns: Human < Cattle < Fish < Birds
Selenium supplementation for cattle routine Application of incorrect molecular form of selenium may have negative effects on yield
Application of cattle waste to agriculture can have negative side effects depending on cattle feed
Increased attention from FWS, USDA, and EPA for agricultural runoff resulting in higher costs for industry over time
Acknowledgments
Thanks! to:
Brooks Applied Labs staff
Dr. Hakan Gurleyuk