Poor Recoverability From SPE

Discussions about sample preparation: extraction, cleanup, derivatization, etc.

2 posts Page 1 of 1
Hi All,

I am trying to use SPE to concentrate river water (4L) to a high enough concentration that I can quantitate pharmaceuticals using GC-MS. The drugs I am looking at are estrogenic hormones (E1, EE2, E2, E3). However, before I can go out to get samples I am trying to verify my SPE-GC-MS method, and am having trouble with recovering my analyte.

To do this I am spiking ultra-pure water with one estrogen (E2) as a test at the concentration of 500ng/L. After SPE extraction my GC-MS is telling me that I only have about 35% of that. To make sure the GC-MS method worked, I tested the stock today and got the correct value.

Here is how I am doing the SPE:
Cartridge: C18, 0.5g, 3mL
Pretreatment: MeOH (4mL), EtOAc (4mL), and H20 (4mL)
Flow: ~7.5mL/minute using a Vaccum Manifold
Elution: MeOH (12mL)
Drying: Vaccufuge (7.5 hrs, 45 Deg C)
Reconstitution: Pyridine (1mL)

Thank you,
Troy
You may want to reference this EPA method

https://www.organomation.com/sites/defa ... %20539.pdf

It is used for finished drinking water, 1L extraction but using LCMSMS, so you may need a different final solvent.

As for your current procedure, maybe use Ethyl Acetate first, then Methanol in the wash steps since Methanol is more soluble in water. You could have some Ethyl Acetate remaining in the sorbent keeping the sample from making good contact. For pesticides we wash with Ethyl Acetate, then Methanol, then DI water before introducing the sample.
The past is there to guide us into the future, not to dwell in.
2 posts Page 1 of 1

Who is online

In total there are 2 users online :: 0 registered, 0 hidden and 2 guests (based on users active over the past 5 minutes)
Most users ever online was 599 on Tue Sep 18, 2018 9:27 am

Users browsing this forum: No registered users and 2 guests

Latest Blog Posts from Separation Science

Separation Science offers free learning from the experts covering methods, applications, webinars, eSeminars, videos, tutorials for users of liquid chromatography, gas chromatography, mass spectrometry, sample preparation and related analytical techniques.

Subscribe to our eNewsletter with daily, weekly or monthly updates: Food, Environmental, (Bio)Pharmaceutical, Bioclinical, Liquid Chromatography, Gas Chromatography and Mass Spectrometry.

Liquid Chromatography

Gas Chromatography

Mass Spectrometry