Margrete Lie (Presenter)
St.Olavs Hospital, Trondheim
Bio: I am a Medical Laboratory Technologist working at the department of Medical biochemistry at St. Olavs Hospital in Trondheim. I mainly work with steroid hormones and method development on the LC-MSMS systems.
Authorship: Margrete Lie
Department of Medical Biochemistry, St. Olavs Hospital HF, Trondheim University Hospital, Norway
| Short Abstract After implementing a new LC-MSMS method for aldosterone in serum into routine use, we detected a reoccurring interference in about 3-5 % of the samples. We were unable to identify this interference and ended up making an alternative method for these samples. |
Long Abstract
1. Problem
An LC-MSMS method for Aldosterone in serum was developed using ESI positive mode and initially we saw no interferences. After the method was implemented in the routine a co-eluting peak appeared in some samples. This co-eluting peak is detected by deviating qualifier ratios.
2. Method information (original method)
• Liquid Liquid Extraction (LLE) of serum with MTBE
• Agilent 1290
• Agilent 6490AA
• ESI, positive mode
• Column: C18, 2.1 x 50 mm, 2,7 µm
• Column oven: 50 °C
• Injection volume: 20 µL
3. Troubleshooting step
Interference is most likely an analyte not normally present in human serum. This is most likely a drug that some of the patients take. Looking at the other steroid hormones, naturally and synthetic, there are three good candidates. We tested for interference with cortisone, prednisolone and prednisone. All these eluted after aldosterone and with good baseline separation. Over a period of time we monitored medicine status for most of the patient with this interference, and found that all were taking prednisolone. This led us to believe that the interference could be a metabolite of prednisolone.
4. Outcome
We made an alternative method to handle these patient samples and this seems to work. The alternative method has a longer biphenyl column. This gives us good separation between aldosterone and the interfering peak with correct qualifier ratio.
Since the original method has a really good sensitivity that cannot be achieved by the alternative method we chose to keep the original method for the majority of samples and use the alternative method to reanalyze only those samples who presented with the interference. Although this seems to be working it is a temporary solution and it would be good to know what this interference is so that we may get rid of it.
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