Are you utilizing Picarro’s mesh inserts for seawater? At what temperature do you hold the vaporizer?
Christopher R. Maupin, Ph.D.
Stable Isotope Geosciences Facility (SIGF)
Texas A&M University
E. [log in to unmask]
3147 TAMU, College Station, Texas, U.S.A. 77843-3147
> On Jul 13, 2018, at 1:34 PM, mwolhowe <[log in to unmask]> wrote:
> I've got a Picarro with a standard autosampler/discrete injected sample vaporizer setup. We've been having increasingly bad precision with the thing that no amount of method optimization will seem to address. I know there's a million things that can go wrong with a few-year-old Picarro (pump problems, the dreaded need-for-$20k-cavity-cleaning-or-allignment, etc), but we typically run saltwater samples and I figure the vaporizer is a good place to focus my attention first.
> Symptom: increasingly poor precision in both D/H and 18O, significantly worse when injecting saltwater samples than freshwater samples, no amount of needle cleaning or swapping will help. Regular vaporizer cleaning (warm water flushes) used to help but are becoming necessary increasingly frequently and are starting to make no real difference.
> I have noticed white precipitate in the injector, right under the septum, that warm water flushes will not remove. I've cleaned that out manually, because I can reach it, but I can only assume the vaporizer chamber itself and/or the transfer line is full of this stuff.
> Picarro mentions that if water is not sufficiently cleaning out the vaporizer to try 'other solvents'. I think methanol is mentioned in the case of organic contaminants. My question to the community is, what sorts of 'other solvents' have you used/do you know are safe to use for mineral buildup? I feel like it may be necessary to run weak acid through it to remove these salts, but I'm obviously terrified of that.
> I've had it suggested to me that I try an ammonium bifluoride solution to get rid of silicates and metal oxides (apparently a common mineral buildup when evaporation of seawater is a feature of your instrument). Does anyone have any experience with this? I'm not super excited about the potential to be playing with what amounts to a weak HF solution and then pouring it through the instrument. Or running other (non HF) acids/bases through the thing to clean out resilient minerals?
> Any thoughts? Thanks!
> Dr. Matthew Wolhowe
> Research Scientist/Engineer III
> Lab Manager, Oceanographic and Geochemical Stable Isotope Facility
> School of Oceanography
> College of the Environment
> University of Washington