-----Reply to Rick Johnston's post-----

From: watoo prohmpittayarat [mailto:watoop@...]
Sent: October 17, 2002 7:45 AM
To: arsenic-crisis-owner@yahoogroups.com
Subject: Hello Arsenic-crisis group

Hello Rick Johnston
I'm a Thai people.I interest to created Arsenic test kit.
I'm a Pharmacist.I tried to created them to test drug and water.
I want sensitivity ~0.04 ppm. and least danger.
I study in USP, NF and more.Their 're so low sensitivity & used danger
chemical.
Have you get me a new idea.
Thank you so much
Watoo

-----Rick Johnston responds-----

Dear Watoo:

Most field kits convert arsenic in water to arsine gas, which then comes
in contact with some chemical which changes color, such as mercuric
bromide. Unfortunately, the chemicals required are toxic, as is the
arsine gas itself. There are some details about the different chemicals
that can be used in the USEPA ETV evaluations:

1) http://www.epa.gov/etv/pdfs/vrvs/01_vr_AS_75.pdf
2) http://www.epa.gov/etv/pdfs/vrvs/01_vr_AsTopHE_AAA.pdf
3) http://www.epa.gov/etv/pdfs/vrvs/01_vr_quick.pdf

There is more information on the Quick test at the manufacturer's web
site:

http://www.acustrip.com/specs/specs481396.html

The United States Geological Survey has a explanation of analytical
techniques for arsenic measurement. Most are laboratory techniques, but
you might find the references useful:

http://wwwbrr.cr.usgs.gov/Arsenic/FinalAbsPDF/taylor.pdf

For many years the Asian Arsenic Network has produced an inexpensive
field test kit. It is described in detail at their website, and
instructions are given for making your own reagents as well:

http://www.asia-arsenic.net/as3as5/ASKITNEW.HTM

These sites should give you some good information about the chemical
procedures that have been most effective. If I were you, I would
consider the possibility of purchasing kits from one of these providers.
The manufacturers have already gone through a long process of trial and
error, and you can benefit from their experiences rather than having to
go through all of the pain yourself. Why re-invent the wheel?

You will probably want to identify a reference laboratory in Thailand
that can verify field kit performance, using a technology such as atomic
absorption spectrophotometry (AAS). Also, be warned that many kits
work quite well on laboratory standards, but give much poorer results
for natural waters. As(V) can be more difficult to measure than As(III)
with field kits. Your verification tests should include natural waters
spiked with various amounts of As(III) and As(V).

Best of luck in your efforts -

Rick Johnston