EPA 300.1 Seawater samples pre-treatment

Discussions about sample preparation: extraction, cleanup, derivatization, etc.

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I need to remove chloride anions from seawater samples. So i dilute my sample x100 (cannot dilute more since i raise a lot my MDL) and then i use Metasep Ag+ SPE cartridge to remove chloride but:

1.When i use them on my standards (e.g. 2ppb chlorite + chlorate in Type 1 HPLC Water) the procedure seems to INCREASE the amount of chloride of the standard (without pre-treatment my water contains about 5ppb chloride and then it goes to 30ppb approximately). The recoveries on my 2ppb standards of chlorite and chlorate are above 90%.

2. When i use them on my samples it seems that i get much lower recoveries with the following paradox. If i pass my sample through two in series of those cartridges i detect a higher amount of chlorites than i do when i pass my sample through one of those cartridges.

Has anyone use such cartridges in such matrices? Am i using them wrong? Is it something else inside my sample that interacts with the AG+? Thanks in advance and sorry for my bad english.

P.S. Before using the cartridge on the sample i pass about 3mL Type 1 HPLC water. I use them manually and i pass about 1 drop (0.05mL) per second
I think the plastic housings for many filter cartridges tend to contribute Cl to aqueous samples - this is a problem that goes back to the 1980s if not further.
Check with your SPE vendor, they may have a pretreatment routine that helps.
Thanks,
DR
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DR wrote:
I think the plastic housings for many filter cartridges tend to contribute Cl to aqueous samples - this is a problem that goes back to the 1980s if not further.
Check with your SPE vendor, they may have a pretreatment routine that helps.



Thanks a lot!!!!
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