I have a problem in determination ppb level of fluoride in approx. 10000ppm sulphate solution. I used the Dionex 300 system with AS-4A column, but fail. Any suggestion?

I'm not sure why you posted this in an archive section of this site but perhaps if I knew a bit more about your situation I could better answer this question. Nevertheless, in the absence of the details I can still give you a summary of your options: your best option is to switch to a column with better fluoride retention than the AS4A column. There are a number of column options that will most likely allow you to accomplish your objective including: the AS14A and the AS9-HC if you are interested in sticking with carbonate-based eluent systems. If you are interested in switching to hydroxide, then probably the best choice would be the AS18 column. Considering the relative concentrations, you might find it necessary to use an eluent step change to achieve sufficient resolution of fluoride from the injection void while still achieving an acceptable analytical run time. This strategy might also be applied to the AS4A column as well. In this case, you can start with 1mM sodium carbonate and then step to 5mM sodium carbonate at the retention time of fluoride. Of course, the AS4A column is a fairly low capacity column so you would most likely be more successful with a high capacity column such as the AS14A.

I moved this thread from the archives to the main LC message board.
- Admin

Thank a lot Chris.
Can I use the standard bore pump on my DX300 for the micro-bore column AS14A?

yes