Transcript PowerPoint presentation by Professor Julian Tyson

The Arsenic Project
Chemical Measurements in Support of
Studies of the Biogeochemistry of Arsenic
Julian Tyson
Department of Chemistry
UMass Amherst
MA 01003
[email protected]
http://courses.umass.edu/chemh01/
Outline of “The Arsenic Project” talk
Background to my involvement.
Background on arsenic: environment and health
Pressure treated wood
Arsenic in water
Other sources of arsenic
Middle school and undergraduate researchers.
Measurement problems: soils and water
High tech: HPLC- HG-ICP-OES; low tech: test strips
What is research?
Background to “The Arsenic Project”
Loughborough U. 76 - 89: UMass 89 - present
J. F. Tyson , S. G. Offley, N. J. Seare, H. A. B. Kibble
and C. Fellows, "Determination of arsenic in a nickel
based alloy by flow injection hydride generation atomic
absorption spectrometry incorporating by continuous
flow matrix isolation and stopped flow pre-reduction
procedures," J. Anal. At. Spectrom., 1992, 7, 315-322.
Peter Yehl: my first student to work on issues of
arsenic (from pressure-treated wood) obtained his
Ph.D. in 1996. Since then, at least one Ph.D. student has
worked on arsenic-related topics every year.
Background to “The Arsenic Project”
Started with trying to answer the question, “What
happens to the arsenic that leaches out of wood
pressure-treated with chromated copper arsenate?”
Three hypotheses: (1) it forms insoluble compounds
with soil, (2) it is washed away by surface water runoff, and (3) it evaporates, because soil bacteria
convert it to volatile methylated compounds.
Needed methods to measure the various arsenic
compounds in soils. Turned out to be very difficult!
Background to “The Arsenic Project”
This led to my suggestion that tracking the arsenic
from PTW as part of an “arsenic in the environment”
theme would be a suitable for our GK-12 program.
Started in summer of 2002.
Needed a procedure for the determination of arsenic to
support studies by the middle-school student
participants.
Issues: cost, safety, limit of detection (LOD), speed
Picked the Hach version of the “Gutzeit” test designed
to measure As in drinking water.
Background to “The Arsenic Project”
Awareness of the PTW source led to my suggestion
that tracking the arsenic from PTW as part of an
“arsenic in the environment” theme would be a suitable
for our GK-12 program. Started in summer of 2002.
Needed a procedure for the determination of arsenic to
support studies by the middle-school student participants.
Issues: cost, safety, limit of detection (LOD), speed
Picked the Hach version of the “Gutzeit” test designed to
measure As in drinking water. But it has limitations.
Background to “The Arsenic Project”
Can we do better? This led to a research project,
supported by NSF, into the possibility of pervaporation
with visible spectrophotometry. Started in fall 2003.
Also an interest in the general need for inexpensive,
reliable, field-deployable, simple, technologies for the
determination of arsenic at realistic concentrations
i.e. with an LOD of < 10 ppb (or ng mL-1 or mg L-1)
Fall 2004. Creation of authentic research experiences
for first-year undergraduates--more info at the arsenic
project website: http:://courses.umass.edu/chemh01/
Background to “The Arsenic Project”
Mandal and Suzuki, “Arsenic around the world” Talanta,
2002, 58, 201-235.
Uses: insecticides, herbicides, desiccant (cotton
production), wood preservative, feed additive,
medicine, poison, bullets, electronics, glass, paints,
wallpapers and ceramics.
Our quality of life affected by the extent to which we
can (a) minimize the harmful effects of naturally
occurring chemicals, (b) exploit beneficial effects of
chemicals with which we choose to interact.
Update on “The Arsenic Project”
“The World Health Organization (WHO) recommends
a tolerable daily intake of 50 µg/kg body weight from
food and no more than 20 µg/L in the drinking water
(WHO, 1983).”
http://www.prn.usm.my/sites/arsenic.html (accessed
April 2005).
Update on “The Arsenic Project”
Chemical form or speciation is all important.
E.g. Sodium is nasty, chlorine is even worse.
But swap an electron between them and make sodium
chloride, and the resulting compound is essential.
Not quite the same for As, as there are no known
essential compounds (in humans).
But there is a very wide range of toxicities.
Update on “The Arsenic Project”
Chemical form or speciation is all important.
The most toxic are arsenite, As(OH)3, arsine AsH3 and
the methylated forms of AsIII. MMAIII and DMAIII
CH3
As
OH
OH
CH3
As
OH
CH3
These are more toxic than the corresponding +5 species,
which in turn are more toxic than arsenate, As(O)(OH)3
Intake of 70 to 300 mg of arsenic trioxide may be
fatal. Death typically occurs between 12 to 48 hours but
can occur within one hour. Those who survive arsenic
trioxide poisoning may develop encephalopathy or severe
peripheral neuropathies.
Symptoms of acute poisoning usually occur within one
hour of ingestion but may be delayed for up to 12 hours,
particularly in the presence of food. The principle toxic
effects are hemorrhagic gastro-enteritis, profound
dehydration, cardiac arrhythmias, convulsions, muscle
cramps, shock and death.
http://www.gettingwell.com/drug_info/nmdrugprofiles/nutsupdrugs/ars_0
026.shtml (accessed April 2005)
Toxicity from dietary intake of arsenic—up to 60 µg/day
daily—is relatively low. Intakes of higher amounts of
arsenic on a chronic basis may cause hyperkeratosis,
especially of the palms and soles, skin pigmentation,
eczematous or follicular dermatitis, edema (especially of
the eyelids), alopecia, muscle-aching and weakness,
stomatitis, excessive salivation, anemia, leukopenia,
thrombocytopenia, jaundice, cirrhosis, ascites, peripheral
neuropathy, paresthesias, proteinuria, hematuria and
anuria. Chronic-high arsenic ingestion has been associated
with various cancers, such as basal cell carcinoma and
bladder, liver and lung cancers. The nail changes
associated with arsenic toxicity are known as Mees' lines
or transverse striate leukonychia.
 Abnormal levels exist in:
Argentina, Australia, Bangladesh, Chile, China,
Hungary, India, Mexico, Mongolia, Peru, Thailand
and the United States of America
 Adverse health effects documented in:
Bangladesh, China, India (West Bengal), Mongolia
and the United States of America
 Arsenic in drinking-water will cause 200,000 –
270,000 deaths per year from cancer in
Bangladesh alone.
Arsenic contaminated water revealed in 1993
4.5 million tube wells
Arsenic contamination in 20% of those tested
Environmental Health Perspectives, 2005, 113, A379
Recent studies estimate that 2-100 children per million
exposed to PTW during early childhood may develop lung or
bladder cancer later in life as a result of this exposure
Consumer Product Safety Commission (2003)
Some arsenic compounds are not so bad.
Some of the good guys
Salvarsan: used to treat
syphilis until the advent of
penicillin in the 1950s
Neoarsphenamine: used in the treatment of
syphilis until the advent of penicillin in the 1950s.
Melarsoprol: currently used in treatment of sleeping
sickness, Trypanosoma brucei rhodense and gambiense.
May also cure chromic lymphocytic leukemia.
As2O3 is used to treat acute promyelocyte leukemia,
chronic myeloid leukemia and some cases of lymphoma or
esophageal cancer.
J. Chem. Educ., 2003, 80, 497
Roxarsone: growth promoting
and antibiotic agent in
poultry. Annual emission
estimated to be 900,000 kg.
4-hydroxy-3-arsanilic
acid
p-arsanilic acid or 4-
aminophenylarsonic acid
The end of the metabolic path?
trimethylarsine oxide
TMAO
tetramethylarsonium
iodide
Arsenosugars:
Found in urine
and seaweed.
arsenobetaine AsB
Present in high concentrations in seafood
arsenocholine AsC
Background to “The Arsenic Project”
According to a recent NSF report: About 80% of
school students decide, by the time they enter high
school, that they are not interested in science.
And: environmental topics improve student interest,
attitude, achievement and attendance.
Can be applied at all stages of the curriculum from K-21.
S. Pfirman and the AC-ERE “Environmental Education in the Complex Environmental
Systems: Synthesis for Earth, Life and Society in the 21st Century, A report
summarizing a 10-year outlook in environmental research and education for the
National Science Foundation, 2003, p. 44.
http://www.nsf.gov/geo/ere/ereweb/acere_synthesis_rpt.cfm (accessed April
2005).
Student Activities in “The Arsenic Project”
http://courses.umass.edu/chemh01/
Undergraduates: Now in 5th semester. Each group has 2-3
freshmen and 1-2 juniors and a graduate student mentor.
Final reports from spring semester 2006.
1. Removal of Arsenic from Drinking Water: Chemical Means: Arsenic Removal by Iron
Precipitation in Alkaline Solutions
2. Arsenic (III) Removal from Water via Coagulation with an Iron Species
3. Measurement of Arsenic in Hair and Nails
4. Spectrophotometric Determination of Arsenic in Water: Flow injection molybdenum
blue method
5. Spectrophotometric Determination of Arsenic in Plants: The Molybdenum Blue Method
Student Activities in “The Arsenic Project”
6. Spectrophotometric Determination of Arsenic in Pressure-Treated Wood: Silver
diethyldithiocarbamate method
7. Determination of arsenic in wood by inductively coupled plasma mass spectrometry
using oxalic acid extraction: the mapping of copper chromated arsenate wood on the
University of Massachusetts Amherst Campus
8. Metabolism of Arsenic in E. Coli
9. Analyzing the spatial distribution of arsenic in soil using the Hatch Test Kit and soil
from the Amherst area
10. Effectiveness of Solvents in the Removal of Arsenic from Soil
11. Evaluating and Improving a Commercial Test Kit for the Determination of Arsenic in
Drinking Water
http://courses.umass.edu/chemh01/
Student Activities in “The Arsenic Project”
http://courses.umass.edu/chemh01/
Current arsenic-related research in the Tyson group.
Primary topics
Fate of arsenic leached from CCA pressure-treated wood.
Study of the transformations of arsenic compounds by
microorganisms.
Study of the uptake of arsenic by plants.
Study of the interaction of the in vivo interaction of
arsenic and selenium
Graduate Student Activities
Improved procedures for the determination of arsenic
and arsenic compounds in waters, soils, plants and other
biological systems.
Improved against the usual criteria: cost, speed, accuracy,
precision, multi-analyte capability, detection limit,
selectivity, sensitivity, signal-to-noise ratio, cost
effectiveness,
Both at high tech end (HPLC with plasma source emission
or mass spectrometry) . . .
and at the low tech end (naked eye detection).
Graduate Student Activities
Secondary Topics
Mapping of As distribution in local communities.
PTW, soil and ground water
Removal of arsenic from drinking water.
Waste biomass
Biomarkers of arsenic exposure
Hair, nails, and earthworms
Rahman et al.,“Effectiveness and Reliability of
Arsenic Field Testing Kits: Are the Million Dollar
Screening Projects Effective or Not?” Env. Sci.
Technol, 2002, 36, 5385-5394.
290 samples: FTK vs HG-AAS vs Ag-DDTC; false negatives were
as high as 68% and false positives up to 35%.
2,866 samples from previously labeled wells: HG-AAS; 45%
mislabeling in the lower range (< 50 ppb),
for 70 - 600 ppb, 4 - 10% mislabeled
“Millions of dollars are being spent without scientific
validation of the field kit method. Facts and figures
demand improved, environmentally friendly laboratory
techniques to produce reliable data.”
Caldwell, et al. “Searching for an optimum solution to
the Bangladesh arsenic crisis,” Social Science &
Medicine, 2003, 56, 2089–2096..
“The reason for caution about precipitating a great suspicion
of tubewells or a rapid turning against them is that no
alternative source of water may prove very satisfactory.”
“the most urgent need is not changing the source of water but
comprehensive national water testing providing essential
information to households about which wells are safe and
which are not . . . all progress depends on nationwide testing
and retesting of all tubewells, a process that has hardly
started.”
Hossain “Arsenic Contamination in Bangladesh—An
Overview,”, Agriculture, Ecosystems and Environment,
2006, 113, 1-16
2.5 million tube wells, 128 million people
“No-one has devised practical methods of ground
water remediation, most studies and actions have
focused on testing tube well water for arsenic.”
“Field kits used to measure As in the region’s
groundwater are unreliable and that many wells in
Bangladesh have been labeled incorrectly”
Melamed, “Monitoring As in the environment: a review
of science and technologies with the potential for field
measurements”, Anal. Chim. Acta, 2005, 523, 1-13.
“Accurate, fast measurement of arsenic in the field
remains a technical challenge. Technological advances in a
variety of instruments have met with varying success.
However, the central goal of developing field assays
that reliably and reproducibly quantify arsenic has not
been achieved.”
What’s the problem?
A procedure capable of the reliable on-site determination
of arsenic in ground water at single digit ppb
concentrations is needed.
Can be used on site by inexperienced operators.
Costs nothing.
Field deployable criterion rules out the best technique:
atomic spectrometry
Candidates: electrochemistry, solution
spectrophotometry, and Gutzeit-type test kits
Spectrophotometric methods?
Two candidates: (a) molybdenum blue, and (b)
silver diethyldithiocarbamate
Arsenate + molybdate + acid + reducing agent gives
blue color due to formation of heteropoly species
containing both MoIV and MoVI.
Arsenate converted to arsine, evolved and trapped in
a solution of AgDDC in non-aqueous solvent containing
a base. A red color forms due to colloidal silver
formation
Spectrophotometric methods?
Two candidates: (a) molybdenum blue, and (b)
silver diethyldithiocarbamate. Both have
problems as basis of field deployable procedure.
AgDDC complicated.
Molybdenum blue has possibilities but reaction is
slow and non-specific. There is current activity: e.g.
Dhar et al., “A rapid colorimetric method for
measuring arsenic concentrations in groundwater,”
Anal. Chim. Acta, 2004, 526, 203-209
Dhar et al., “A rapid colorimetric method for
measuring arsenic concentrations in groundwater,”
Anal. Chim. Acta, 2004, 526, 203-209
There are still some issues to be sorted out.
“one peculiarity of the formation of As-molybdate
complexes encountered during this study is that samples
containing very little P must be spiked to at least 2 µmol L-1
P (i.e. to ~0.05 absorbance for a reduced aliquot) because
of a P dependence of the rate of color development for
As.”
Could the method be adapted to a non-instrumental finish?
Maybe.
Matsunaga et al., “Naked-eye detection of trace arsenic in
aqueous media using molybdenum loaded chelating resin
having b-hydroxypropyl-di(b-hydroxyethyl)amino moiety”
Talanta, 2005, 66, 1287-1293
The color developed fully after heating for 4 h at 40 oC.
The 20-min (45% max color) detection limit was 1 x 10-6
mol dm-3
But this is only 75 ppb.
Prospects:
Cardwell et al. “Pervaporation flow injection determination of arsenic
based on hydride generation and the molybdenum blue reaction” ACA,
2001, 445, 229-238. Determination of arsenic by pervaporation flow
injection hydride generation and permanganate spectrophotometric
detection, ACA 2004, 510, 225-230.
Our approach: Pervaporation into an
acceptor solution containing iodate and
permanganate with detection by visible
spectrophotometry. Performance was
superior to those of procedures based on
(a) the molybdenum blue chemistry, which
requires on-line heating, and (b)
pervaporation into permanganate alone.
LOD 0.5 ppb
Gutzeit test?
Arsenate + zinc + acid produces AsH3. Soluble in water to 780
mg/L, but dissolved salts and H2 evolution transferAsH3 into head
space. AsH3 reacts with mercuric bromide impregnated test strip.
Yellow-brown color produced after set time is compared with
preprinted chart.
Modifications to Hach Test
“Field test kits offer the only plausible approach for mass
screening” Kinniburgh & Kosmus, Talanta, 2002, 58, 165-180.
Speed up reaction by HG with borohydride?
Improve accuracy and precision by increasing the time
to 24 h?
Read color by scanning and interrogating the RGB
values of image pixels?
Mathews et al, “Quantitative assay for starch by colorimetry
using a desktop scanner,” J. Chem. Educ. 2004, 81, 702-704.
Speed up reaction by HG with borohydride?
Added a side-arm to vessel to add
borohydride solution,
Needed to add a lot of
borohydride to overcome the
demand by “oxone”.
Without this reagent: color
development in 15 min. More
intense colors in 30 min.
Stirring also helps.
Twenty-four hour version of test
Current test kit does not detect below 10 ppb
Response in 10 – 50 ppb range inconsistent
Signals observed for 1, 3, 5, 7, 10, 15, 20 ppb
1 ppb response was clearly different from that of the
blank
24-hr technique not reliable for  15 ppb.
Suggests a way of tuning the range of responses based
on choice of time before reading strip.
RGB values of scanned test strips
Images of test strips from std 30-min tests on 0 ppb to
500 ppb As solutions obtained with a desktop flatbed
scanner.
Images (in color JPEG format) evaluated by software
developed by Mathews et al. COLORS.EXE that
calculates the average red, green and blues intensities
of the pixels within the area selected.
Three different resolutions: 400, 800 and 1200 dpi
Mathews, et al., “Quantitative assay for starch by colorimetry using a
desktop scanner,” J. Chem. Educ. 2004, 81, 702-704.
250
Resolution 400
Resolution 800
Resolution 1200
B Value
200
150
100
50
0
0
100
200
300
400
Concentration (ppb)
500
600
Prospects. Maybe sensing based on quartz crystal
microbalance is possible?
Mirmohseni & Alipour, “Construction of a sensor for the determination
of cyanide in industrial effluents: a method based on quartz crystal
microbalance,” Sens. Actuators, 2002, 84, 245-251.
Frequency of oscillation of a piezoelectric quartz crystal is
dependent on the mass. Manufacturer’s literature suggests
that mass changes of 1 ng can be detected.
The referred literature does not really support this. Also
suggests that frequency changes due to factors other than
mass, such as visco-elasticities of interphases, are more
important.
We’ll find out.
HPLC-HG-ICP-OES
Argon
MSIS
Column
2-Channel
HPLC pump
Sample
Injection valve
ICP
HCl
Pump
A
B
Mobile phases
NaBH4
Pump
Sample flow rate 1ml/min
Argon flow 0.55 l/min
NaBH4 0.5% in 0.1% NaOH
NaBH4 flow rate 1.5 ml/min
HCl 16 M flow rate 0.05 ml/min
J. Anal. At. Spectrom., 2002, 17, 1540–1548
Waste
Baseline separation of four key compounds
Sequential extraction procedure
0.2 g soil to 15 ml centrifuge tube
5 ml 0.1 M phosphoric acid added and shake for 24 h
Centrifuged for 10 min at 70 rps
Supernatant filtered through 0.45 µm filter and inject
5 ml 0.1 M sodium hydroxide was added: shake for 24 h
Centrifuged for 10 min at 70 rps
Supernatant filtered through 0.45 µm filter, adjust pH to
2.5 and inject.
Soil contain As(III)
25
Phosphoric acid
Concentration (ug/g)
20
sodium hydroxide
Total extract
15
10
5
0
As(III)
DMA
MMA
As(V)
Total
Soil contain As(V)
25
Phosphoric acid
Concentration (ug/g)
20
sodium hydroxide
Total extract
15
10
5
0
As(III)
DMA
MMA
As(V)
Total
25
Concentration (ug/g)
20
Soil contain DMA
Phosphoric acid
sodium hydroxide
Total extract
15
10
5
0
As(III)
-5
DMA
MMA
As(V)
Total
Soil contain MMA
25
Phosphoric acid
Concentration (ug/g)
20
sodium hydroxide
Total extract
15
10
5
0
As(III)
-5
DMA
MMA
As(V)
Total
Soil contain Mix
80
Phosphoric acid
Concentration (ug/g)
70
60
sodium hydroxide
Total extract
50
40
30
20
10
0
As(III)
DMA
MMA
As(V)
Total
The arsenic project: acknowledgements
NSF awards DUE 0139272 Graduate Students in GK-12
Education (GK-12) “STEM Connections”, June 2002 and
is currently in a no-cost extension period.
NSF 0316181 “Integrating Research and Education:
tracking arsenic from pressure-treated wood” started
in July 2003.
UMass Center for Teaching: Faculty Grant for Teaching.
Sept 2005.
Camille and Henry Dreyfus Foundation: Special Grant
Program in the Chemical Sciences. Feb 2006.
The arsenic project: facts and figures CCA
Percentage of Type A
Component
min max
Type B
min max
Type C
min max
CrO3
59 - 69
33 - 38
44 - 51
CuO
16 - 21
18 - 22
17 - 21
As2O5
15 - 20
42 - 48
30 - 38
300,000 metric tons of inorganic arsenic have been
used for wood preservation since 1975.
The arsenic project: facts and figures
PTW. As of December 2003 is no longer sold.
Up till then about 2 x 108 ft3 of wood pressure-treated
with CCA was made every year.
Depending on formulation the material contains 4.0, 6.4
or 13 kg m-3 of CCA.
The acute lethal oral dose is 1 - 2.5 mg kg-1.
For 75 kg adult this is 75 - 188 mg.
This is, for best case scenario, 313 cm3 or a cube 7 cm
on the side. Worst case scenario: 2.3 cm cube.
The arsenic project: facts and figures
Total arsenic in PTW was measured to be 0.2% i.e. 2,000
ppm i.e. 2,000 mg kg-1 or 2 g kg-1
To get a minumum lethal dose: eat 3.8 g of wood.
If density is 0.5 g cm-3. This is a 2-cm cube.
Katz and Salem, J. Appl. Toxicol., 2005, 25, 1-7.
The density of arsenic trioxide is 3.74 g cm-3. A 100 mg
lethal dose is a cube of side 3 mm.
The arsenic project: facts and figures
About 35 µg cm-2 of As can be dislodged from aged
PTW.
The Hach test kit can detect 500 ng (just). 35 µg in 50
mL is 700 ppb (top end of the scale).
Contaminated soil might contain 40 ppm. If a 1-g sample
is taken, the mass in test kit would be 40 µg (800 ppb).
The arsenic project: facts and figures
Cost of Hach EZ test kit:
$50.60
(100 tests and 2 reaction vessels with caps, plus reagent
to eliminate sulfide interference)
Reagent set for 100 tests:
Reaction vessel (one):
Cap (one):
$33.00
$5.50
$2.50
Shipping;
$14.00
Research: Creation and Dissemination of New knowledge
How is research done?
By: scientists working in industry, government labs, and
universities and colleges.
Most organizations have a large number of research groups,
whose members collaborate. Most groups are relatively small
(< 10).
Groups are dynamic. New members join; older members move
on. Leadership is stable.
New members learn from the more experienced members.
Research: Creation and Dissemination of New knowledge
New members need training:
Background to problem (big picture, what is already
known),
How to find out (library)
Techniques to be used,
Hypothesis to be tested,
Plan of action (experimental design)
Communication skills (written and oral)
Research: Creation and Dissemination of New knowledge
How is new knowledge communicated?
Within members of research group.
Conference presentations (oral or poster).
Scientific literature: reviewed journal articles.
Researchers write manuscripts, submit to journal editor.
Editor sends to reviewers.
Reviewers send back comments (anonymously).
Researchers revise.
Article is published and work is scrutinized.
Recent work is reviewed periodically by experts who write
“review articles”.
Important stuff eventually finds its way into textbooks.
Research: Creation and Dissemination of New knowledge
Importance of chemical analysis.
Many investigations need information about chemical
composition of relevant materials.
Often it is difficult to provide this information.
All researchers need to know about the scope and
limitations of chemical measurement methods.
Often these are set by the instrument that is to be
used.
An authentic research experience involves:
Working on a real problem,
Over an extended time period,
Working in a team with more experienced workers,
Finding out about your topic,
Devising a plan of work,
Conducting experiments and interpreting the results,
Devising new experiments,
Sharing your findings
by writing and talking about what you are doing/have
done.