Arsenic in Food -...

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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


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!


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).


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


How are Methyl Arsenic Compounds Formed?

Biological methylation reactions require alternating reduction and oxidation steps


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…


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


Many Methods AvailableHydride Generation w/Cryotrapping & AASHydride Generation & AFSLiquid Chromatography & ICP-MS

Anion exchange chromatographyReverse phase ion pairing chromatographySize exclusion chromatography


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


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


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


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!


Study Materials

1) White Rice

2) Brown Rice

3) Kelp

4) Apple Juice


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


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


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


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


As Speciation(as function of total As in extract)


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�


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)


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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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!

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