HPLC Rezex ROA-Organic Acid Column

[nitinbana]

we are using a new rezex roa column... accidently we rinsed the injection syringe with MEOH and then injected the samples with it .... now we are not getting the lactate and acetic acid peaks... is their any way to recover...



nitin.

[tom jupille]

Those columns are not tolerant of methanol in the mobile phase, but injecting a small amount (such as carryover in your syringe) should not damage the column. In any case, the usual symptom is a dramatic increase in pressure (in essence, the packing bed shrinks in the presence of methanol).

Is your pressure OK? Are the other peaks eluting at the expected retention time?

[nitinbana]

yes pressure is ok 570psi during entire process... i doubt that probably the tubings had acetonitrile in them from last run ... though i purged for 10 minutes i doubt 10 minutes purging was not sufficient... could it be due to left over acetonitrile... OXALIC acid peak is comingon its position 8.8 minutes... but system was not able to even detect acetate and lactate peaks upto 30 minutes... any help plz...

[nitinbana]

after the system was by some other guy with c18 and acetonitrile.... i connected the WATER tubing with my H2SO4 and than purged for 10 minutes... do you see any problem... tubing carrying acetonitrile was not used... although internal tubing might be having some leftover acetonitrile that i purged for 10 minutes...

[tom jupille]

Acetonitrile should not be a problem. In large concentrations in the mobile phase (up to about 50%) it *decreases* retention. At low concentrations (< 1%) it has a negligible effect.

As I indicated earlier, methanol in the sample is generally not a problem (in fact, that column can be used to analyze alcohols). In the mobile phase it causes catastrophic bed shrinkage. But that does not seem to be your problem.

Since oxalic seems to be eluting properly, are you sure you actually have the appropriate concentration of sulfuric acid in your mobile phase? That will affect the retention of the weaker acids.

[nitinbana]

i prepared 0.005N H2SO4, 70 microlitre of 98% 1.84kg/L H2SO4 added in 500ml of miliQ water.... than filtered with PVDF membrane and de-gased for 2 hr..... pH i chacked with pH strips its coming pH 1....