Back to the Top
Dear members,
I am working in the field of drug discovery in DMPK division. We are
working on an NCE for which we have used sum of multiple ions in the
quantitation of analyte by LC-MS/MS in plasma matrix.
Does anybody have used this quantitation option in regulatory work or
does anybody have published an analytical method in which they have
used this option?
Citations of publications are highly appreciated.
Thanks,
--
Shivva Vittal,
Jr.Scientist,
Dept. of Drug Metabolism and Pharmacokinetics,
Discovery Research,
Dr.Reddy's Laboratories,
Miyapur, Hyderabad,
India.
Back to the Top
Dear Shivva,
Using sum multiple ions for quantitation purpose to increase the
sensitivity of an analyte is quite OK. You can select all the
prominent plausible product ions from your full scan product ion
spectrum and can put in the MRM acquisition method. There are also
instances where the same parent to product transition has been
monitored for many times to increase the signal. As long as you are
applying the same quantitation method for the whole batch and your
Standards and Quality Control samples are meeting the acceptance
criteria, I dont think there is any problem in going ahead with sum
multiple ions.
Hope it helps.
Regards
Neel K Mohan
Back to the Top
Dear Shivva,
I am not aware of the regulatory aspect but I dont see any problem as
long as you satisfy the recommended guidlines for bioanalytical
validation. You might want to look at the following reference in
which summing up ions was used to increase the sensitivity of the
method.
M. Nitin, M. Rajanikanth, J. Lal, K.P. Madhusudanan, R.C. Gupta,
Liquid chromatography-tandem mass spectrometric assay with a novel
method of quantitation for the simultaneous determination of
bulaquine and its metabolite, primaquine, in monkey plasma, Journal
of Chromatography B, 793, (2003) 253-263.
Having said that, here are few downsides (at least from my
perspective ! ) on this approach:
1. You have to show specificity for your compound for all the MRM
transitions that you choose.
2. Intensity of the transitions should not differ by a large
magnitude, else you encounter linearity issues at low concentrations.
3. Method becomes more sensitive in a sense that because there are
multiple ions involved, fluctuation in any one of those will affect
your method.
Hope it helps
Regards
Nitin Mehrotra
Dr. Nitin Mehrotra, Ph.D
Post Doctoral Research Fellow
Department of Pharmaceutical Sciences
University of Tennessee Health Science Centre
Memphis, Tennessee, USA-38105
901-448-3385 (Lab)
901-448-6940 (Fax)
nmehrotr.-a-.utmem.edu
Back to the Top
Dear Shiva,
I agree with Nitin's suggestions. Select only stable MRM transitions
to avoid the fluctuation in signal intensity. Use full scan mode,
apply collision energy required to fragment the parent ion and
simultaneously see the fragments' relative intensity. Select those
fragments which have stable relative intensity. We have applied this
technique in pre-clinical toxicokinetic studies successfully.
Regards,
Jignesh S. Kotecha
Scientist 1
Bioanalytical Division,
BE Centre,TRC.
Back to the Top
The following message was posted to: PharmPK
Dear Jignesh,
I understand summing multiple ions will increase sensitivity. But can
you tell us how many fold improvement you achieved by incorporating
sum multiple ions technique?
Vinayak Nadiger
Manager , Bioanalytical Chemistry
11 Biopolis Way, Helios #08-05
Singapore 138667
E Mail: vnadiger.-a-.combinatorx.com
Back to the Top
Dear Vinayak,
You would get increase in counts (peak area increase) approximately
proportional to relative intensity of fragments in addition to what
you get from single major fragment.
regards,
Jignesh S. Kotecha
Scientist 1
Bioanalytical Division,
BE Centre,Torrent Research Centre.
Gandhinagar, India.
Back to the Top
Dear shivva,
Here your sum of multiple ions in the quantitation of analyte by lcms/
ms is possible only through certain software like thermo, which is
not possible by any other software like analyst 1.4.1.
As far your quires concerned about weather you can use sum of
multiple ion
for quantitation or not, which is totally depends on your analytes
specifity ,and its intensity.
for example:
if an analyte have Q1 VALUE as 500 and whose Q3 VALUE may be
300, 200, 100 respectivly, after full scan mode.
any one out of this three QI/Q3 ratio , whose LLOQ VALUE shows
signal to noise ratio (S/N) is more than 5 as per guidlines, showing
good reproducible value then you should select that Q1/Q3 VALUE.
Sum of multiple ion in the quantitation of respective analyte can
be use if its response ,specificity, sensitivity and intensity are
cope up.
if analytes intensity is not showing any fluctuation in sum of
multiple ions quantitation then you may go ahead with your analyte.
with lots of hope
Muthuswamy.C
Executive analyst
Bioanalytical section,
welquest clinical section
Nicholos Piramal India ltd.
Back to the Top
Dear Muthu,
I could not understand your explanation to the full extent and just
trying to explain about the use of sum multiple ions in quantitation.
Also to let you know, this feature is very much there in the
quantitation wizard of Analyst v1.4.1.
Just to explain the practical scenerio, suppose the parent ion mass
of a particular analyte is m/z 466.1 and has three prominent product
ions at the m/z of 305.4, 258.9 and 192.6. Now for quantitation
purpose you can keep all the three transitions of Parent to Product
in the acquisition method as
466.1>305.4
466.1>258.9 and
466.1>192.6
By doing so, you can increase the overall response of the analyte
which in turn will enable you to go for lower quantification limit.
One factor which needs to be considered while going for sum multiple
ions is that if any particular transition is giving a high background
noise and/or false response for the blank matrix sample, then the
same transition is better not to be used for quantitation. Now, when
to go for sum multiple ions is totally need based and provided you
have enough data set to prove the accuracy and precesion of your
method with this particular method of sum multiple ions, you can
always go ahead with this procedure.
Hope it helps.
Regards
Neel K Mohan
Back to the Top
Hi Muthuswamy,
What Neelkamal pointed out is correct. Using Summing ions is not a
software issue. Analyst 1.4.1 (API 4000) and also Masslynx
(Micromass), both are capable of using the summing of multiple ions
in MRM mode very effeciently.
Regards
Nitin
Dr. Nitin Mehrotra, Ph.D
Post Doctoral Research Fellow
Department of Pharmaceutical Sciences
University of Tennessee Health Science Centre
Memphis, Tennessee, USA-38105
nmehrotr.-a-.utmem.edu
Back to the Top
Dear muthuswamy,
The summation of multiple ions is possible using analyst 1.4.1 software.
Dear Shivva,
You can certainly use the summation of multiple ions option. We have
used it for a couple years back for Submission bio-studies. If
possible use fragment ions greater than 100 m/z for better specificity.
Dr. Mandar Mote
Head Bio-analytical
CRO
Cadila Pharmaceuticals Ltd.
Ahmedabad
Want to post a follow-up message on this topic?
If this link does not work with your browser send a follow-up message to PharmPK@boomer.org with "Summation of multiple ions in LC-MS-MS quantitation" as the subject | Support PharmPK by using the |
Copyright 1995-2011 David W. A. Bourne (david@boomer.org)