What do you mean by "under the condition of As(III)"?

 seperate AsV from AsIII;

The company SUPELCO makes a 2 ML reversible tube with PE frits that is filled with an unknown material "500 MG DSC-SAX". If you contact the company they will be able to help you.

An As speciation cartridge may help you as the attachment.

 We did have this cartridge made by Mengxiaoguang,but  under strong ionic strength environment,like seewater,it didn't work well.Recently,i have foucued my attention on amino-functionalized silica,some articles report its good selectively on arsenate.

OK. This is an interesting and important issue.

Hello Pan,

This question was asked a while back. Have you found a solution? If so, I would be curious to know what worked for you. Just off the top of my head, I wonder if filtration steps would work?

For instance, reverse osmosis systems are very effective at removing As(V), but not as effective at removing As(III) from water. Perhaps a similar system could be adapted to selectively discriminate arsenic species. Perhaps by increasing the pH so that As(V) has a double negative charge while the As(III) specie remains neutral.

Hope this helps,

Cheers!