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Measurments or cleaning a hexapole?

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Topic: Science  |  Series: My Journey to PhD
Hexapol připraven na ultrazvukovou lázeňThe Thursday's work in lab was so gorgeous and just according to the plan that I could have been in a strong suspicion something would go wrong on Friday eventually. The betrayal of the intrument came in the form of the afternoon spent with the ion optics cleaning.

I am actually working on a project aimed at the analysis of the tetracycline antibiotics in the environmental waters. On Thursday I successfully incorporated the internal standard to the method and tuned the mass spectrometer parameters for it. For Friday I planned to measure through the matrix effects.

Matrix effects are a relatively novel problem in mass spectrometry - electrospray ionization (ESI-MS) analyses. They are seen as signal enhancement or suppresion caused by compounds present in the sample matrix (plasma, water, urine etc.) They disable precise quantification of the analytes. In one publication I have read recently the matrix effects were reffered to as the Achilles heel of mass spectrometry quantification.

Also the Friday lab work began very well. Several injections of the mixture of the analytes and the internal standard confirmed the suitability and correct setting of the method. I set ten blank samples to be injected in order to get rid of any possibly present overlefts of the analytes, which would spoil the analysis of the matrix effects. However, ten blanks appeared not to be enough. After another two hours of washing no imrovement was reached. Moreover I started to have problems with an instable baseline of the chromatogram. My colleague Hanka had similar problem earlier on that week. That was the reason why we decided to contact the service center of Waters. Their advice sounded vigorously: clean the ion optics - clean the hexapole!

I have never seen let alone done the cleaning of the ion optics. Hanka was much more experienced on this field: she saw twice a service-man to perform the procedure. :-) Nevertheless, there was nothing else left to do but clean it on our own. When part of the instrument was allready dismantled, we changed and cleaned also the sample cone and the capillary.

Hanka does the maintanence of the latter two routinely. So she kindly let me to change them. With her help and instructions it was no problem for me. To take out the hexapole we watched a "How To Video" from Waters website. It was very detailed and thanks to it all problems were avoided. After the cleaning procedure (hexapole was immersed into methanol and ultrasonicated for 30 minutes) and drying, it was time to install the hexapole back on its place.

We did very well and we put back also all the tiny parts that might be seen on the included photos. At the end we had to check whether the mass spectrometer works without problems. The trial analysis run as it was supposed to and after four hours we could have claimed the technical part being successfully over. We prepared 10% mixture of formic acid in methanol and used it for washing the instrument overnight.

I left school on Friday being full of contradictions: I did no progress in my project. The technical problems delayed it for once again. On the other hand I have learned many new things about the mass spectrometer maintanence and I found out that me and Hanka are able to solve some complications merely on our own. And that was the satisfaction I needed! :-)

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