The Arsenic Project Chemical Measurements in Support of Studies of the Biogeochemistry of Arsenic

Background on arsenic: environment and health Pressure treated wood Arsenic in water Other sources of arsenic Middle school and undergraduate researchers.. Started with trying to answer

The Arsenic Project Chemical Measurements in Support of Studies of the Biogeochemistry of Arsenic

Julian Tyson Department of Chemistry

UMass Amherst

MA 01003

tyson@chem.umass.eduhttp://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 stripsWhat is research?

Background to “The Arsenic Project”

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

Loughborough U 76 - 89: UMass 89 - present

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 run-off, 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 g 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

Background to “The Arsenic Project”

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

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.

Salvarsan: used to treat

syphilis until the advent of

penicillin in the 1950s

Some of the good guys

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 aminophenylarsonic acid

4-trimethylarsine oxide TMAO

tetramethylarsonium iodide

The end of the metabolic path?

Arsenosugars: Found in urine and seaweed.

arsenocholine AsCarsenobetaine AsB

Present in high concentrations in seafood

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 21 st 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

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

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

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 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.”

“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.”

Hossain “Arsenic Contamination in Bangladesh—An

2006, 113, 1-16

2.5 million tube wells, 128 million people

“Field kits used to measure As in the region’s

groundwater are unreliable and that many wells in

Bangladesh have been labeled incorrectly”

“No-one has devised practical methods of ground

water remediation, most studies and actions have

focused on testing tube well water for arsenic.”

Melamed, “Monitoring As in the environment: a review

of science and technologies with the potential for field

“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

Candidates: electrochemistry, solution

spectrophotometry, and Gutzeit-type test kits

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

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

AgDDC complicated

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?

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

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.