by» Wed Sep 21, 2005 5:49 am
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from my experience it is mostly the inlet check valve that fails.
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most of the time also the cause is salt precipitation inside of it.
the best manner of dealing with the problem is to flush the check valve with water. most of the time you also have to do manually with a syringe.
the best solution is prevention. do the least mixing with the instrument itself, and always check what is the ratio salt/organic that your method will sustain without precipitating the salt. that is where i have seen many R&D's "sin".
this salt precipitation happens when you work with 2 channels of eluents, one 100% salt/ buffer and the second 100% organic, and the mixing is performed in the instrument. or also when you have a buffer/organic solution in channel one and you perform a fast gradient to the second channel which is 100% organic.
if your instrument starts the mixing within the proportion valve chamber, then this problem will happen to you relatively rarely. in the long run you will harm your proportion valves.
intruments of this type are dionex, shimadzu, varian for example.
if your instrument has four distincted proportion valves then the mixing will start only at the mixer.
in that case you risk having your inlet check valve clogged with salt often. instrument of this type that i know is hitachi.
another problem that check valve will cause when they ware down is noise on the detector and bad reproducability of RT and or area of peaks.