low presure

[Solediga]

I have a nitrates in acid extract (H2SO4 0.5 M) from anionic exchange resin, These extracted were neutralized with a NaOH (3N), and after these where filtered (0.22 um) and finaly I determined nitrates by ion cromatography.
I used a ICPak HR 4.6 x 75 mm; 6um (Waters) column using sodium borate/gluconate eluent and flow rate of 1ml/min and temperature in the column at 35ºC.
After to running 250 samples, the presiure increased. I believe that the column has a precipitates, but I don´t know how to eliminate these precipitates in this column ?
And I don´t know what are happen?

Can you help me.

[Mark Tracy]

I have found that good quality borate salts are hard to obtain, and insoluble contaminants are common. It is safer for your column, and actually faster to prepare from boric acid and sodium hydroxide. (Of course, filter your mobile phase.)

If you are lucky, only the entrance is fouled, and you can clear it by back-flushing or replacement of the frit. Check in with Waters before doing that.

[Chris Pohl]

Solediga,

If you still have this problem, you might also want to try an acid cleanup. Since your sample is an acid extract you might have base insolubles in your extract. The column is acrylate based but should be ok with brief exposures to 1M acid (1hr exposure should be ok).