By Anonymous on Sunday, March 14, 2004 - 05:15 pm:
Do anybody have idea about liquid/liquid extraction of lisinopril from human plasma for performing LC-MS/MS. I found only SPE. How much recovery will be?
By AllsepTech on Sunday, March 14, 2004 - 08:09 pm:
Why are you trying to extract lisinopril? Did you try direct injection of your plasma smaple? Can you provide more details.
By Anonymous on Monday, March 15, 2004 - 02:50 am:
I am also thinking for direct injection of plasma sample after protein precipitation using ACN. But I am not sure whether it will work or not? In most of the articals, they used SPE extraction. I have to analyze plasma samples of bioequivalence study, using LC-MS/MS.
I will be thankful for you on getting suggestion of direct injection. Protocol and mobile phase composition.
Thanks in advance.
By AllsepTech on Monday, March 15, 2004 - 09:05 am:
I am trying to find a source of lisonopril to try it on our Primsep D column which is designed for direct plasma analyis. Do you know were I can get a sample to develop method for you? Check this link may be you can draw conclusions for your analysis
http://www.allsep.com/Technology_DirectPlasmaAnalysis.php
Contact us if you have any questions.
By Uwe Neue on Sunday, March 21, 2004 - 08:32 am:
This may be a bit late, but we have developed generic protocols for the direct injection of plasma samples using LC/MS/MS as the separation/detection tool. The technique uses Oasis HLB or MCX cartridges, 2 mm x 2 cm. The sample is injected at high flow rate, 4 mL/min, and then a rapid 1-minute gradient is run at 0.4 mL/min to elute the sample into the MS.
Methods of this type have been used in our lab for several years now. They are reliable, reproducible, quantitative, and simple. Go to the Waters website and check under Oasis applications! I can also send you several publications that demonstrate variants of this technique.
By DK on Monday, March 22, 2004 - 05:33 am:
Never mind being late!
I am worried for direct injection, but thinking for future. I have few concerns in your suggestions. HLB of MCX cartridges you suggest, it will be almost solid phase extraction. I think you are trying to suggest direct injection of eluted sample (without drying it). Am I right?
Other, you recommended high flow (4ml/min), I am not sure whether it will be compatable with the ESI source, or not. Again you suggest for gradient run.
I am currently using 50mmX2, 3 um hydrosphere, with 0.2 ml/min flow, isocratic. I used 1cc (30mg) HLB for extraction. I successfully developed method having 1ng detection limit.
Anyway, your suggestion is good. If you send me your protocol, it will be helpful for me to understand your method.
Hoping for your mail.
By Uwe Neue on Monday, March 22, 2004 - 02:34 pm:
No, this is not solid phase extraction, this is real chromatography, albeit on a large particle. Some people call it on-line solid-phase extraction, but in the simplest case, we do not use an analytical column. Due to the execution of the gradient, we have sufficient resolution and sufficiently narrow peaks to go directly into the MS system without a second column.
The high flow is used for the washing step, not for the elution step. The elution step is performed at MS compatible flow, i.e. 0.4 mL/min or thereabouts. The wash step is isocratic, at 4 mL/min, typically with 0.5% organic solvent. We do not elute the junk that is removed at high flow into the MS system, but to waste. This is best done using a switching valve and a separate isocratic pump for the wash.
By Anonymous on Monday, March 22, 2004 - 09:11 pm:
Thank you for making me clear. So you are using swiching valve. I donot have more idea about performing analysis using switching valve. If you can, please send the protocol.
With regards
DK