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www.brooksrand.com
Arsenic in Food
Presented by Michelle BriscoePresident & Technical DirectorBrooks Rand Labs
Presented November 8, 2013Costco International QA & Food Safety SummitIssaquah, Washington
•Small analytical chemistry firm located in Seattle
•Exclusively focused on metals in food & the environment
•ISO 17025 Accredited
Primary Metals of Concern
The “Big 4”• Total Arsenic (As)• Total Cadmium (Cd)• Total Lead (Pb)• Total Mercury (Hg)
Metals Speciation
• USP Metals• Selenium Speciation• So Much More!
< 10 ppb detection available using ICP-MS method
Other
• Inorganic Arsenic (iAs)• Methylmercury (MeHg)
MEANINGFUL METALS DATAwww.brooksrand.com 206-632-6206 [email protected]
Metals Speciation
What is Metals Speciation? Analytical quantification of the different forms that a metal
is present in
Why is Speciation Important? Different forms of metal can have different characteristics:
– Toxicity– Bioavailability– Mobility– Treatability
MEANINGFUL METALS DATAwww.brooksrand.com 206-632-6206 [email protected]
Arsenic SpeciationA Hot Topic Recently (and not so recently…)
The forms of arsenic found in fish are very different from the forms of As found in rice:
Organic As - predominant form is seaweed, fin fish, kelp, shellfishInorganic As - predominant form in rice, produce, groundwater
Fish with 500 ppb As = YUM!
Rice with 500 ppb As = YIKES!
MEANINGFUL METALS DATAwww.brooksrand.com 206-632-6206 [email protected]
Arsenite, As(III)
Toxic carcinogensInorganic Arsenic Forms
Arsenate, As(V)
AsO33-AsO43-
Inorganic As is classified as a known human carcinogen by the Agency for Toxic Substances and Diseases Registry (US ATSDR), the Environmental Protection Agency (US EPA), and the World Health
Organization’s International Agency for Research on Cancer (IARC).
MEANINGFUL METALS DATAwww.brooksrand.com 206-632-6206 [email protected]
Potentially toxicMethylated Arsenic Forms
Dimethylarsinic acid, DMAs
Monomethylarsonic acid, MMAs
Also called cacodylic acid, DMAs is formed in the liver after
ingesting inorganic As
MMAs(III) may be more toxic than As(III), while MMAs(V) is less
toxic
MEANINGFUL METALS DATAwww.brooksrand.com 206-632-6206 [email protected]
How are Methyl Arsenic Compounds Formed?
Biological methylation reactions require alternating reduction and oxidation steps
MEANINGFUL METALS DATAwww.brooksrand.com 206-632-6206 [email protected]
Other Organic Arsenic FormsRelatively non-toxic
Roxarsone is a controversial arsenic compound used as a nutritional supplement for
chickens and swine
Arsenobetaine very common As compound and is the main
source of arsenic found in fishArsenocholine is found in many
marine organisms
AsB Roxarsone AsC
And MANY others…
MEANINGFUL METALS DATAwww.brooksrand.com 206-632-6206 [email protected]
Toxicity of Different As Species
Toxicity of individual arsenic species is dependant on:• The general form (e.g., inorganic vs. organic)• The oxidation state of the arsenical• The organism’s detoxification mechanisms and
bioaccumulation factors
MMAs(III) > As(III) > As(V) >> MMAs(V) = DMAs(V) > DMAs(III) >> AsB = AsC = arsenosugars
As(III) is about 300 times more toxic than AsB
For the speciation of arsenicAnalytical Methods
MEANINGFUL METALS DATAwww.brooksrand.com 206-632-6206 [email protected]
Many Methods AvailableHydride Generation w/Cryotrapping & AASHydride Generation & AFSLiquid Chromatography & ICP-MS
Anion exchange chromatographyReverse phase ion pairing chromatographySize exclusion chromatography
MEANINGFUL METALS DATAwww.brooksrand.com 206-632-6206 [email protected]
Many Methods AvailableHydride Generation w/Cryotrapping & AASHydride Generation & AFSLiquid Chromatography & ICP-MS
Anion exchange chromatographyReverse phase ion pairing chromatographySize exclusion chromatography
MEANINGFUL METALS DATAwww.brooksrand.com 206-632-6206 [email protected]
HG - CT- GC - AASPros Determines Inorganic As with a
quick, easy, and inexpensive method Decades of proven reliability Codified in EPA Method (for water
and fish) Good for measuring iAs in samples
high in AsB and AsC Very sensitive: < 0.1 ppb for water samples < 3 ppb for solid samples
EPA Method 1632Cons Operationally-defined As(V) determined by calculation
[Inorganic As – As(III)] Very labor intensive Cannot measure AsB, AsC, arseno-
sugars While common in environmental
sectors, less common in food testing labs
MEANINGFUL METALS DATAwww.brooksrand.com 206-632-6206 [email protected]
IC - ICP - MSPros Measures many different forms
directly and simultaneously with anion exchange Reasonably sensitive:
< 0.2 ppb for water samples< 20 ppb for solid samples Lots of options for columns, mobile
phase, etc. outlined in the literature Usually, just one extractant works
well for all species
Cons Prone to interference from chlorides
– use interference reduction technology such as DRC or collision cell with ICP-MS High AsB can swamp DMAs and
As(III) results Some organic compounds are
better determined by cation exchange, requiring a 2nd method Expensive equipment Relatively new to a lot of labs – still
some issues with species identification and co-elution
www.brooksrand.com
2013 Brooks Rand LabsInterlaboratory Comparison Study for Arsenic Speciation in Food and Juice
MEANINGFUL METALS DATAwww.brooksrand.com 206-632-6206 [email protected]
Goals of the Study
To provide a reliable means for laboratories to evaluate their competency at quantification of arsenic species in food
To provide a metric for assessing the intercomparability of arsenic speciation data generated by different laboratories
MEANINGFUL METALS DATAwww.brooksrand.com 206-632-6206 [email protected]
Key Features of the Study
broad invitation to participate
no participation fee
large group of participating laboratories from around the world
anonymous data submission
inclusion of analytical method reporting
SELECTED STUDY MATERIALS
Criteria for selection: Foods that were “hot” topics
for arsenic Must have > 10 ppb in total
arsenic Minimal processing required Cheap
THANKS TO US FDA, UC DAVIS, AND AGILENT TECHNOLOGIES
FOR THEIR ASSISTANCE!
MEANINGFUL METALS DATAwww.brooksrand.com 206-632-6206 [email protected]
Study Materials
1) White Rice
2) Brown Rice
3) Kelp
4) Apple Juice
MEANINGFUL METALS DATAwww.brooksrand.com 206-632-6206 [email protected]
2013 Intercomp Study Schedule
January Sample procurementFebruary Sample screening for total arsenicFebruary 7th Registration opensMarch More sample procurement & screeningApril 1st Samples shipped out to labsJune 7th Deadline for results submissionJune 14th Anonymized data delivered to BRLAugust 26th Final report for study issuedAugust 27th Study results presented at AOAC International
Annual Meeting in Chicago, Illinois
Region Number of Participants
North America 25 64%
Europe 8 21%
Other 6 15%
International Participation
MEANINGFUL METALS DATAwww.brooksrand.com 206-632-6206 [email protected]
Analytical Parameters for Study
Total Arsenic (As) in the sample Total As in the extract (if applicable) Inorganic As As(III) - arsenite As(V) - arsenate MMAs – monomethylarsonic acid DMAs – dimethylarsinic acid Other arsenic species, such as arsenobetaine (AsB) or
unknown arsenic species
MEANINGFUL METALS DATAwww.brooksrand.com 206-632-6206 [email protected]
Data Analysis
Each laboratory was asked to report the following for each sample and analyte: Analytical result Detection limit Date analyzed Data qualifier (limited to u and nm only) Detailed methodology information
MEANINGFUL METALS DATAwww.brooksrand.com 206-632-6206 [email protected]
Results
M Values (μg/kg)
Total As in
Sample
Total As in
Extract As(III) As(V) Inorg As MMAs DMAs AsB
White Rice Flour 40.70 39.90 25.91 (6.49) 30.15 (2.86) 8.49 ND
Brown Rice Flour 52.46 54.00 33.00 11.15 38.90 (2.75) 7.71 ND
Kelp Powder 63700 59335 (3790) 20924 23763 (1530) (1467) 3837
Apple Juice 16.64 14.57 1.84 12.50 13.95 (0.60) (0.35) ND
MEANINGFUL METALS DATAwww.brooksrand.com 206-632-6206 [email protected]
As Speciation(as function of total As in extract)
MEANINGFUL METALS DATAwww.brooksrand.com 206-632-6206 [email protected]
Statistical Analysis
Based on USGS procedure for round robins http://bqs.usgs.gov/srs/SRS_Spr04/statrate.htm
Z-Value Calculation
Z = |(X-M)|/F and F = Q/1.349Z = absolute Z-value assigned to each result for assigning a ratingX = reported value M = median value reported by all laboratories (excluding NDs)F = F-pseudosigma (approximates the Std Dev)Q = Interquartile range
http://bqs.usgs.gov/srs/SRS_Spr04/statrate.htm�
MEANINGFUL METALS DATAwww.brooksrand.com 206-632-6206 [email protected]
Description of Ratings
Rating Absolute Z-value
4 (Excellent) 0.00 – 0.50 3 (Good) 0.51 – 1.00 2 (Marginal) 1.01 – 1.50 1 (Poor) 1.51 – 2.00 0 (Unacceptable) Greater than 2.00
Scores were not assigned if:- the overall number of data points was less than seven- the variance (F-pseudosigma value) was greater than the
median value (M)
MEANINGFUL METALS DATAwww.brooksrand.com 206-632-6206 [email protected]
Overall Mean Scores
Parameter Mean Score n
Total As in Sample 2.6 136 Total As in Extract 2.7 79 As(III) 2.6 88 As(V) 2.8 72 Inorganic As 2.7 122 DMAs 2.9 49 All Parameters 2.6 546
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All Matrices
MEANINGFUL METALS DATAwww.brooksrand.com 206-632-6206 [email protected]
Mean Scores by Matrix
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Brown Rice
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White Rice
MEANINGFUL METALS DATAwww.brooksrand.com 206-632-6206 [email protected]
Mean Scores by Matrix
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Kelp Powder
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Kelp Powder
MEANINGFUL METALS DATAwww.brooksrand.com 206-632-6206 [email protected]
Lessons Learned & Future Work (for next year?) Inconsistent reporting of inorganic arsenic Potential misidentification of some forms of arsenic Unable to ship materials to Mexico More expensive than anticipated
Study report is available upon request, and is currently being prepared for submission to a peer-reviewed journal for publication
Next Year?
www.brooksrand.com
THANK YOU!ANY QUESTIONS?
Arsenic in Food��Presented by Michelle Briscoe�President & Technical Director�Brooks Rand LabsSlide Number 2Primary Metals of ConcernPrimary Metals of ConcernMetals SpeciationArsenic SpeciationInorganic Arsenic FormsMethylated Arsenic FormsHow are Methyl Arsenic Compounds Formed?Other Organic Arsenic FormsToxicity of Different As SpeciesAnalytical MethodsMany Methods AvailableMany Methods AvailableHG - CT- GC - AASIC - ICP - MS2013 Brooks Rand Labs�Interlaboratory Comparison Study for Arsenic Speciation in Food and Juice�Goals of the StudyKey Features of the StudySelected Study MaterialsStudy Materials2013 Intercomp Study ScheduleSlide Number 23Analytical Parameters for StudyData AnalysisResultsAs Speciation�(as function of total As in extract)�Slide Number 28Statistical AnalysisDescription of RatingsOverall Mean ScoresMean Scores by MatrixMean Scores by MatrixLessons Learned & Future Work (for next year?)THANK YOU!