May I presume that you have already tried the old classical methods? If I remember correctly, you can form the phosphomolybdate under highly acidic conditions and then extract it into, for example, ethyl acetate or butanol/chloroform. The extraction is quite selective relative to e.g. arsenic and silicate species. I think you can then release the phosphate again by going to high pH. Does this help any? David Pranitis -- USDOE/Environmental Measurements Laboratory 201 Varick St., Floor 5 New York, NY 10014 (212) 620-3605