There are a small number of procedures that can be used for arsenic
speciation in the field. I suggest the papers by Ficklin, AWWA and
Clifford. The newer papers by Clifford use a commercially
available `prep-disk' that is very easy to use. These are all ion
exchange based separations. There are some commercially available
speciation kits in the US but it is easy enough to build your own. I
can give you more details later.

A combination of field separation and one of the field detection
methods will work. The Arsenator, As-Top and Hach semi-quantitative
tests, and Biotest can all quantify inorganic arsenic in ion exchange
eluant. Brand new on the market are TraceDetect devices that use
anode stripping potential that can do inorganic speciation. ETV
Battelle is currently validating several of these tests and results
are expected soon. The lowest detection you will get in a field
method is about 1-5 ppb. Some speciation methods result in sample
dilution

To the best of my knowledge, none of the field tests can quantify any
of the organic arsenic compounds such as MMAA and DMAA. You have to
use one of the hyphenated IC separation methods or pH dependant
hydride generation. You might be able to add a digestion in the
field. Some of the field methods will separate organic arsenic but
most count it in the As3+ fraction. To separate `organic arsenic' in
the field you can oxidize a portion of the `As3+' aliquot, adjust the
pH again (~2.5) and subject it to another separation. The problem is
the multiple dilutions and matrix effects from oxidizers lower the
sensitivity of some detection methods

Costs are variable. Field speciation will cost ~$10-50 per sample to
build the kits yourself. The low end is inorganic only, the high end
is As3, As5, MMAA and DMAA (combined). To buy speciation kits is $60-
150 each kit. Detection is also variable in cost. Instrumental
methods are $5000-10000 plus reagents. Semi-quantitative HgBr based
color kits are $2-10 per sample.

I hope this gives you a start. Good Luck!

Gregory P. Miller