Hello,

We are working on an LCMS urinary hormone panel.

We are seeing degradation (we suspect oxidation) of Estrogen analytes including 2-hydroxy-estrone, 4-hydroxy-estrone, 2-hydroxy-estradiol, estrone, estriol, estradiol.

The stocks are prepared in methanol and stored in -20C and dark. We see degradation occurring as soon as a few weeks when they should be stable for months.

Preparing calibration curve in synthetic urine, the analytes barely last 10 days stored at 4C and dark.

Have tried adding vitamin C (ascorbic acid) in order to quench the catechol activity and redox activity of radicals/oxygen.

During sample prep the samples are treated with enzyme, extraction on SLE and then derivatized with dansyl-chloride in acetone/bicarb buffer. The samples barely last 24hrs in the autosampler set at 4C.

2 and 4-hydroxy-estrone are isobars and the chromatogrpahy shows good separation when the samples/stocks are fresh, but then degradation results in the peaks merging or loss of the peak all together.

Anybody have experience or suggestions to stabilize these analytes?

Thank you for your time!