I have experience regarding the SPE for histamine analysis. I used Ambelight CG-50 resin SPE for adsorbed the histamine. Before starting to pass through the SPE, I need to activate the resin by using the 1M HCl. It doesn't work properly without activating step. I guess that, some time you have the same problem. Best wishes

Yes you should try to flush the cartridge with a solvent/conditioner prior to the main extraction.

Do you provide any mixing/vibrations during your test?

regards

G

I am not doing any vibration as for the moment I have just been trying to assess if the cartridge (it does not have any SPE material as I am not interested in that). I think one of the main issue might be the soaking time in the cartridge that probably has an effect on the sorption of the contaminants.

I.e : If I let the contaminants in contact with the plastic and the frits for too long together it might be that contaminants react with the plastic tubes and frit.

Are you sure your analytical method provides consistent results?

How many replicates do you inject? Did you try to analyse the solution you are placing in the cartridge along with the solution which was in the cartridge?

Maybe its imported to explain more detailed what is done from "set the sample solution on to the cartridge" too the step where you get your results. So far it’s not clear what u measure exactly.

First of all, what about the elution? How many ml and which solvent is used?

Second, you use just 3 ml of your sample solution with the pharmaceutics and let it remain in the Cartridges. Depending on your solvent it can evaporate / dry more or less and distort your results.

Third thing that comes in my mind is the elution process itself. I don’t use SPE cartridges a lot, but normally its used to achieve higher concentrations. As an example 1 L of a solution with low concentration of caffeine get through SPE-cartridge and all caffeine should remain on the cartridge material. At the second step a low volume of solvent is used to extract the caffeine from cartridge. For this elution step it’s not imported if the caffeine adsorbed at the frits or at the cartridge material, as long as it can be extracted. I hope i don’t missed anything in your explanation.

To be more precise:

I use a wide range of pharmaceutics at a concentration of 3ug/L in DI water. To check if there is an effect of the cartridge on the experiment, I spiked 3mL of this solution to a cartridge that only contains a frit, no other material. I then elute the 3mL of pharmaceutics through vacuum in a glass vial and then I rinse the cartridge with 7mL of DI water. I then have a total of 10mL that I add 10uL of formic acid and the IS. I then use an online SPE measurement via LC MS MS equipment and verify the adsorptyion difference between the concentration found after the SPE cartridge and the initial concentration (I take 3mL of the standard sol + 7mL DI water + ...). Of course calibration curve is also done. So it seems that the fattier contaminants are actually taken up by either the frit or the plastic of the cartridge.

I know it is a little bit different to Solid Phase extraction as the SPE cartridge is just a way of doing a sort of column experiment with my material but I need to know if the material itself influences the experiment.

Sure it is possible that any pharmaceuticals with a particular type of polarity are adsorbed by the frits or the cartridge itself. But there are some points you have to think about. If you want to know if its influence your results you have to test it with the same treatment as you would do with the normal SPE procedure of your chosen method.

Each SPE method comes with an individual description about:

1. Suitable components for that specific type of SPE material.

2. Conditioning steps with different solvents depending on the SPE material.

3. List of Solvents which are able to elute anything that was adsorbed by the SPE material.

You don’t have described any conditioning steps, so that’s something that has to be added. Even if you don’t use any real adsorbent material in the cartridge, the surface of the frits and the cartridge itself will be influenced by the conditioning as well. So one point is that u never use the same solvent to “trap” and “extract” at the SPE. If u want to know if anything will remain on the cartridge or the frits after the extraction step (I think that is what u want to do) u need to extract it with a solvent that matches the SPE method you want to use later on.

Another problem is the descripted solution you want to use with variety of pharmaceutical compounds and polarity’s. No matter which solvent you decide to use for the extraction there are always some pharmaceuticals with a different polarity which are not getting extracted by your solvent. The same problem with the cartridge material (matching polarity’s) even if u don’t use any adsorbent.

In sum, yes you can measure a differences in the concentration of you solution after the cartridge but the results are not comparable with any SPE method.

So I would propose to divide your experiment in parts, create different solutions for pharmaceuticals with a similar polarity (maybe: high, middle and low). Choose a suitable extraction solvent for each different solution. Then you can proceed as you planned to at the beginning:

1. Conditioning

2. Insert 3 ml of the first pharmaceutical-solution

3. Remove it by vacuum

4. Wash with 7 ml of the suitable extraction solvent

5. Proceed as normal

If you repeat this process with each pharmaceutical-solution you should get meaningful results for a large amount of possible SPE methods.

I hope i could help.

Please see the short instruction film about SPE recorded by Agilent Technologies:

https://www.youtube.com/watch?v=Gkdow0i4F68

Best regards,

Mateusz