I need to extract the As (III) and As (V) in mixture of organic and inorganic As mixture or from seaweed. Are there any way to stop the extraction of AB and organic arsenic compound?
No, I don't, sorry. It is rather popular article, you can read it with the help of google translate. SPE extraction of inorganic As is discussed in BS EN-16278 (type it in google). All the forms of As -- i.e. arsenates, arsenites, methylararsonates, arsenobethaine and so on have quite different pKa's.