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X-Ray Fluorescence _XRF_ for heavy metal analysis

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									              XRF
X-ray Fluorescence Spectrometry
           Tom Murphy

        Qualitative Screening
                  or
        Quantitative Analysis
Major Users of XRF

Geoprospecting
Alloy identification for safety and recycling
Remediation of lead in paint, metals in soil
Waste processing such as oil industry
Forensics for legal analysis
Consumer product analysis
Art and Archeology
Industrial hygiene
More powerful units
have radioactive
source, better detection
levels, fewer
interferences, but are
not usually portable,
and if portable require
licensing
   Hand-held XRF – Thermo Fisher
                   Loan
 -analysis in ~1 minute
 -no extraction or other preparation of
  sample
 -detects ppm concentrations of many
  metals
 -non destructive
 -no cross contamination or fouling of
  sensor
Sample Preparation/Calibration

   The sample matrix can be important

   The best cases really suitable for XRF analysis is the
    ‘atomic mixing level’ that is found in:
   -All liquids (homogenous, one physical phase!)
   -Glass
   -Large crystals (used for “finger printing” gem origins)
   -Most alloys
         Mixing varies from impossible to easy
         -results vary from qualitative to
         quantitative



Oil in mineral        Toxic skin cream     This fish needs a
precipitant           can mix but will     better grinder but
“impossible” to mix   separate, “Cao       can shoot
                      Cap”                 replicates
                       Interferences

A few elements interfere, arsenic and lead can effect
each other, especially in low energy XRFs
-in samples with high lead, low arsenic results will be
unreliable

The Matrix can be an issue. If there is more than 10%
water in a sample, it can either enhance or reduce the
signal. Drying of the sample is required.
Geoprospecting – Pathfinder analysis
-can’t see low concentrations of gold with XRF but can
find co-occurring elements like platinum
Jewelry
-XRF quickly detects Pb, Hg, Cd etc.
-no sample preparation




                                       Found clasps with
                                       >40% Pb
                                       -ingestion has killed
                                       child in USA
                                       -chronic toxicity more
                                       common
Lead Amulets/Curse Tablets -
oral very dangerous, dermal less dangerous but not well
documented, no sample preparation needed for XRF




                                              Roman
   Thai Charm     - Khmer Beads 45% lead      Curse
                                              Tablet
Other Consumer Products?
-cooking ware – old ceramics, poorly made
metal ware
-Degree of extractability is important
-Cooking acidic foods is more dangerous

-1/3rd of toys here are toxic by EU regulations
-a few times toys were removed from US
Stores
                             Porcelain




http://www.environment.gov.au/atmosphere/airquality/publications/ceramics.html
-Lead glazes are most commonly used on earthenware, and on older bone china
and porcelain.
-If they are not properly prepared and fired, lead may leach (i.e. move from the
glaze) into food stored in or on the ceramic ware.
-Acidic foods will accelerate any leaching.
-Ceramic ware with a corroded glaze is extremely dangerous.
-Reheating coffee in an old mug in the microwave is a particularly risky thing to do.
    Cooking Ware/Archeology
   Fall of Roman Empire – one theory of several
   The presence of lead in the drinking water
    leached in from the water pipes, glazes on
    containers that came in contact with food and
    beverages, and food preparation techniques
    could have contributed to heavy metal
    poisoning.
   It was also absorbed through the pores, since
    it was used in cosmetics.
Roman use of lead - as cosmetics, pipes, jewelry, curse
tablets, utensils and cooking pots, and, of course sapa
and defrutum (wine boiled down in lead pots)
Lead levels in bones from the Imperial Roman period had up
to 30 mg/kg, which is three times higher than the level the
WHO considers "very severe lead poisoning."
     Paint
     -lead in paint only found now in developing
     countries
     -essential and easy to mix can of paint
     -to process dried paint on a surface requires
     a more powerful XRF and results are
     qualitative
                               Thai Paint with up to 5% lead



Problem?
Small children put pieces of
old paint in their mouths.
-price of renovation in USA
  Previous Thermo Collaboration

     -processed 675 skin
      creams
     -33% of samples from
      beauty shops exceeded
      guidelines
     -up to 3%Hg


Murphy, T.P., S. Lim, S.P. Huong, K. Irvine, S. Bayen, B, Kelly
and K. Wilson. 2012. Application of Handheld X-Ray
Fluorescence Analyzers to Identify Mercury in Skin Whitening
Creams in Cambodia. J Health Pollut. 3:21-31
              Skin Cream Validation -1




The spiked recovery used DMSO for good mixing.
Quantitative for <2000 ppm Hg
A reduced response for >2000 Hg but still useful.
No certified reference materials available for this analysis.
             XRF Validation -2




Comparison of XRF and ICP-OES is fine
Again, there were no certified reference materials for skin
creams.
There are several standard reference materials for fish etc.
When possible use certified reference materials.
Mercury in Skin Creams in Phnom Penh ppm
    Product Name   Apparent Source Total Mercury
    Eucerin        USA                    23200
    Hua Tha Li     China                  19256
    Chang Chun     China                  18458
    Enjoy          USA                    13800
    Rojzy Jiali    Vietnam                12528
    Yimei Yellow   China                  12014
    Guoyao         China                  11500
    Diamond        Unknown                 6147
    Hua Hin        China                   5454
    Qian Mei       China                   5110
    FC             Cambodia                4979
    Malis          Thailand                3552
    Lulanjena      China                   2990
    Oreal2         Unknown                 2852
    Maly           Thailand                1938
    Japanese       Japan                   1652
    SS-II          Unknown                 1410
    Britney        Cambodia                1223
    Mlis           Thailand                  996
Other cosmetics warrant analysis, management
-a blush containing 878 ppm of cadmium
-users all reacted to it and passed to their friends
Waste disposal
- PVC pipe has 7000 to 9000 ppm of lead
- Should not be burned without emission
treatment
- Similar concerns about future oil and gas
industry wastes




      Environment   Environnement
      Canada        Canada
Other Hydrocarbons, Thermal
Thermal power plants to be fired by Khmer coal
-Sulphur, Arsenic, mercury content?
-risk of acidification in soft water environment

-Mercury in natural gas?
                   Khmer Coal
Source             Mean Sulphur Arsenic      Mercury



Preah Vihear,      8419            30        ND
Cam.
Springfield USA1   32000           9.8       0.12

Appalachian1 USA 280002            351       0.211

Wyoming USA3       6300            2.6       0.13


Units ppm, Khmer coal formed in freshwater, low Sulphur
            Concerns with Coal
The Cardamom mountains are granitic and thus they have little
buffering capacity.
Burning coal produces sulphuric acid.
Without emission treatment acid rain from burning coal in such
an environment could kill most plants and water life
At least the sulphur content is not high
          Fish Anemia Study

-Some fish have more iron content than beef and
  could be used to treat anemia.
-so far <30 species processed for [Fe]

								
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