Chromatography Forum

Hi everyone,

Just curious if others have noticed a similar issue with this instrument or other triple quad LCMS systems.

I have some performance issues when trying to analyze vitamin e acetate (alpha-tocopherol acetate) on the Shimadzu 8060. This system is also used for residual pesticide analysis (oregon/michigan list).

The gist is this - after we run our vitamin e acetate method, we notice a significant drift down in peak areas with our pesticides over the course of the next sequence, down to roughly 50% of the starting intensity after ~20 injections. Quantification ions and reference ions flip in relative intensity for some analytes, requiring a lot of manual peak identification. We are also having difficulty meeting our QC criteria for this reason.

The calibration range on the instrument for vitamin e acetate is 1 - 200 ng/mL. It is a very non-polar molecule. I should point out that this problem happens even after injecting clean vitamin e acetate standards and no samples with any real matrix.

Any insight is appreciated. Thank you!

Did Shimadzu give you a cleaning method to help keep the quads clean?

I was having some mass axis drift on our 8050 and they gave me a method that does a scan with both Q1 ad Q3 to help bake out the quads. It runs after the end of a sequence. Your application specialist at Shimadzu should be able to set one up through a remote connection if you are not sure how to do it.

Another thing I have observed with the 8050 was that the mass axis would drift a few tenths of an AMU as the room temperature changed and it would greatly reduce my abundances. The "Unit" resolution on the Shimadzu is much narrower(about 0.1-0.2 AMU) compared to the "Unit" resolution on our old Sciex which was almost 1 AMU. A quick check of the mass alignment with the tune solution will tell you if that is what is happening after running the Vitamin E Acetate.

It is hard to believe that the quadrupoles could shift so quickly and because a different method is applied. You can still recalibrate the quads and see if the peak area increase. But I rather suspect the HPLC system, the MS source or the first MS optics to be affected. Are you using the same mobile phases for pesticides and tocopherol acetate? Are you switching from ESI to APCI ? Do you clean the MS source between both runs?

Check this out
Vitamins are essential micronutrients to maintain the normal functioning of organisms, but they must be ingested from food because they are not synthesized sufficiently in the body. Deficiencies of vitamins in the body cause symptoms such as disease and growth disorders. Vitamin A is associated with night blindness and skin abnormalities, vitamin D with rickets and osteomalacia, vitamin E with anemia and blood circulation disorders, and vitamin K with hemorrhaging, osteoporosis, etc. Therefore, Nox Vidmate VLC it is very important to accurately analyze the fat-soluble vitamins in foods and supplements. The fat-soluble vitamins are broadly classified into vitamin A, vitamin D, vitamin E, and vitamin K according to their chemical structure and physiological effects. Due to the large number of isomers, good separation is required for fat-soluble vitamin analysis. Here we introduce an example of a simultaneous analysis of fat-soluble vitamins using a supercritical fluid chromatograph (SFC) and triple quadrupole mass spectrometer for detection.

It is really difficult to test and control vitamin e acetate. This is also a cause for my confusion. I think I will find the answer here.

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Just curious. Was there ever a resolution to this problem?

Although the Vitamin E standards were clean, previous and subsequent samples that have heavy (invisible) matrix may really dirty an instrument. I highly recommend diverting to waste all cinematographic eluent before and after the peaks of interest. Some LC-MS/MS allow deactivation of the source voltage to lessen contamination, but diverting the flow to waste keeps the MS much cleaner in my opinion. Most of the source contaminating components are eluted very early (salts) and very late (non-polar organics) in RP chromatography.