I have been using a plain gray SUPELCO SPME fiber for direct immersion in 1% KOH, and in one recent occasion, I left samples running (around 10), and I came back to a broken fiber. I tried to change the fiber for a pdms/dvb fiber, but it got destroyed as well. Is it the liquid matrix? Is it the x,y,z location of the auto sampler arm? What could it be? I ran more than 20 samples in direct immersion before, and I haven't experienced any issue, until now :(
Keywords: GC/MS, SPME, autosampler, bent fiber
I think you already answered the main possibility. Coordinates of the autosampler must be confirmed as well as the septa and liner used should also be checked carefully. Everything in the sample introduction configuration must be fully compatible and properly used. Secondly, storing the SPME arrow and holder with residual KOH without rinsing well may also present some clogging or corrosive contaminant in SPME which may lead to the plunger malfunctioning.
Dear Judith M. López-Aceves
You and İsmail Emir Akyildiz are right in assuming the correct positions and paths of the autosampler arm as the reason.
Unfortunately, I don't know which sampler you used, but I know these problems from CTC/PAL or MPS autosamplers. The older models have an elastic tension cord behind the fiber holder. When it ages and loses elasticity, the fiber is no longer pulled up sufficiently and the needle guide does not stiffen the vial far enough. The fiber then sticks to the edge of the vial. As a result, the fiber cannula kinks and is folded into a Z with the next injection. This process continues with each further injection. With the samplers mentioned, this cord must then be replaced with a new one. This is not difficult and solves the problem with the samplers mentioned. If you are using a different sampler, check the positions by running a sample without fibers.
Good luck and best regards
Joachim Horst
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