Phalates method development by LCMSMS

Discussions about GC-MS, LC-MS, LC-FTIR, and other "coupled" analytical techniques.

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Hai Friends,
I am developing a method for DMP,DEP,DBP,DEHP,DNOP (Phthalates) using LCMSMS at 20 ppb level. Problem is I am not able to eliminate blank interference. I tried with different eluents (0.1% formic acid and acetonitrile, methanol) and columns (C18, C8, phenyl etc). All the cases I am getting blank interference at the same transition of DMP,DBP. Can anybody suggest a solution
What is the source of your blank matrix? Often we get phthalate background in even or good RO/DI water. Usually it requires a special filter pack for low phthalate water. We had to special order them to completely remove the background levels from our water system. Almost anything made of plastic has phthalates in it so it is difficult to keep blanks clean.
The past is there to guide us into the future, not to dwell in.
Thank you James.
we tried initially with 0.1% fromic acid in water and methanol. Then with only methanol. Yesterday we did an experiment with Pure methanol and acetonitrile as diluent. Blank also Acetonitrile. A dip in interference observed. but significant, the requirement is 10 ppb
Try to install a extra column (little) between the mixer and the injector. You will be 2 peaks of each ftalate. The first peak is of your sample and the second is of the contamination.
Francesc

Sorry for my english
Dr. Raman Nanduri wrote:
Thank you James.
we tried initially with 0.1% fromic acid in water and methanol. Then with only methanol. Yesterday we did an experiment with Pure methanol and acetonitrile as diluent. Blank also Acetonitrile. A dip in interference observed. but significant, the requirement is 10 ppb


Have you tried an injection at 0 ul, such that there is no vial involved, just starting the instrument acquisition? There may be an interference coming from the vials themselves.
The past is there to guide us into the future, not to dwell in.
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