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ESI, Waters TOF for steroid identification
Posted: Mon Jan 26, 2015 4:44 pm
by Burrr
I've read that ESI is not the ideal method for assessment of steroid compounds.
If this is the only test method at your disposal, could you identify a steroid compound and get a rough estimate of purity with this method?
Re: ESI, Waters TOF for steroid identification
Posted: Mon Jan 26, 2015 5:46 pm
by Burrr
Does this method make since?
Re: ESI, Waters TOF for steroid identification
Posted: Tue Jan 27, 2015 12:05 pm
by carlo.annaratone
Steroids will not ionize well (if not at all) in ESI. You need APCI for that. Otherwise you could derivatize them.
Re: ESI, Waters TOF for steroid identification
Posted: Tue Jan 27, 2015 4:55 pm
by JMB
Analysis of ergosteroids: VIII: Enhancement of signal response of neutral steroidal compounds in liquid chromatographic–electrospray ionization mass spectrometric …
A Marwah, P Marwah, H Lardy - Journal of Chromatography A, 2002 - Elsevier
... The signal response of moderately polar to nonpolar neutral steroidal compounds in positive
ion mode was ... was extensively used to optimize the LC–MS parameters of chemically pure steroid
derivatives ie ... The sulfate conjugates were analyzed in the negative ion mode (ESI). ...
This describes the use of VERY low acid levels (20-100 ppm) rather than 0.1% v/v.
If you really want to go for it, then try post-column addition of AgBF4, see below
Degradation of vitamin D< sub> 3</sub> in a stressed formulation: The identification of esters of vitamin D< sub> 3</sub> formed by a transesterification with …
JM Ballard, L Zhu, ED Nelson, RA Seburg - Journal of pharmaceutical and …, 2007 - Elsevier
... a doublet signal with ∼1:1 ratio. Some initial feasibility experiments were performed
to investigate the behavior of vitamin D 3 under conditions of Ag + -cationization
ESI LC/MS. To minimize the potential deposition of silver ...
As you noted, suppression of ionization due to co-eluting species is a real issue and is best reduced/avoided by a chromatographic separation (HPLC) prior to MS analysis.
JMB
Re: ESI, Waters TOF for steroid identification
Posted: Wed Jan 28, 2015 1:58 pm
by Gaetan Glauser
Some steroids ionize pretty well in electrospray while others don't. For instance you may even achieve better sensitivity in ESI than in APCI for cortisol, testosterone and of course conjugates. So if this is the only method at your disposal, I would recommend to at least give it a try.
Re: ESI, Waters TOF for steroid identification
Posted: Fri Jan 30, 2015 10:17 pm
by Burrr
Would this be a better method for testing a compound like testosterone?
Would this method be considered a full spectrum test, or a column test. Would the purity that is given from this kind of test be representative of the whole sample, or does it isolate the compound before giving us a purity?
Sample Preparation and Analysis Conditions
A quantitative analysis has been performed with the following conditions:
A weighed portion of the sample was dissolved in Toluene, filtered and then analyzed under the
following instrumental conditions:
Chromatograph: Gas Chromatograph (GC)
(Agilent 7820A with 7693A Automatic Liquid Sampler (ALS))
Column: DB-5MS 30m x 250μm x 0.25μm
Carrier Gas: Helium
Detector: Mass Spectrometer (MS),
Identification in Scan mode scanning from 50,0 D to 500,0;
Quantitation in SIM mode with SIM ions for the detected substance.