Colourimetric/ spectrophotometric method may be a option.

HACH makes a low and high range Arsenic test kit which is fairly inexpensive.

Low range kit (0-500 ppb As):

https://www.hach.com/arsenic-low-range-test-kit/product?id=7640217303&callback=qs

High range test kit (0-4000 ppb As):

https://www.hach.com/ez-arsenic-high-range-test-kit/product?id=7640217305&callback=qs

each kit allows for 100 test to be performed

An alternative method is to utilize a rapid colorimetric method for measuring arsenic. A good paper is by Dhar et al., 2004, A rapid colorimetric method for measuring arsenic concentrations in groundwater, Analytical chimica Acta, 526, pp 203-209.

https://www.ldeo.columbia.edu/~avangeen/pdf/Dhar_ACA_04.pdf

Please look at the following below links which may help you in your analysis:

https://www.ideals.illinois.edu/bitstream/handle/2142/53107/newvolumetricmet00plan.pdf?sequence=2

http://atsherren.faculty.noctrl.edu/chm210/ARSENICC.htm

https://europepmc.org/backend/ptpmcrender.fcgi?accid=PMC1266556&blobtype=pdf

Thanks

Thank you all for your answer.