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Dear all,
Does anybody out there have experience using automated SPE machines that utilise positive-pressure
mechanisms (i.e. injection of air onto a cap-sealed SPE cartridge) rather than a vacuum beneath the
SPE cartridge?
In short, I’ve been trying for some time now to (re)validate an HPLC-MS/MS assay that will
simultaneously quantify the following analytes in human plasma:
* Caffeine
* Paraxanthine
* Dextromethorphan
* Dextrorphan
* Omeprazole
* 5-hydroxyomeprazole
* Losartan
* Losartan carboxylic acid
* Midazolam
* 1’-hydroxymidazolam
* Phenacetin (internal standard)
Unfortunately, the computer that houses the automated SPE machine software (the machine is an ASPEC
XL4 by Gilson) died about a year ago taking with it the specific settings used to originally
validate the assay (there was no back-up!). From some digging around and speaking with company reps,
I’ve gathered that it’s the volume of air that you push onto the sealed SPE cartridge and the
solvent flow rate that has the biggest impact on the recovery of your analytes in a given assay
(assuming you’ve already optimised the extraction conditions around the physiochemical aspects of
the solvents/analytes etc.).
Can anyone comment on what air push values, solvent volumes, flow rates etc. that they have used
with this or similar machines in the past? The SPE cartridges I’m using are 3 mL Oasis HLB 30 mg,
and the conditioning, wash and elution solvents are either water, methanol or 10% methanol in water.
I’ve set the flow rate of the dispensing needles to 0.5 mL/min as per another study in the
literature using this same machine.
Thank you in advance to anyone who can help me with this tricky business!
Shane
SHANE EAGLES | PhD Candidate
Faculty of Pharmacy
THE UNIVERSITY OF SYDNEY and CONCORD HOSPITAL
Building 4 (ANZAC 3)
Concord Repatriation General Hospital
CONCORD
NSW
2139
N372, Pharmacy and Bank Building (A15)
The University of Sydney
NSW
2006
E shane.eagles.aaa.sydney.edu.au
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Dear Shane,
Yes I have experience in my previous organization working with Tecan (an automated liquid handling
system) with negative pressure SPE & its functions are precise and accurate, and now Tecan had
newly added Positive Pressure SPE module also.
The Tecan software features are great, you may look for its demo w.r.t. EVo 150 or 200 model (150 &
200 represent the deck / platform size of equipment).
Thanks
Best Regards
Dr. Deepak Jain
(M.Sc., MBA, PhD)
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