Agilent 8890 inlet contaminated phthalate

rui 14 days ago

We recently did headspace analysis (35C for 15 min) Gerstel MPS on Agilent split/splitless injection port (Agilent 8890 GC-5977B MS). There was some phthalate in the samples, although they didn’t show in the headspace analysis possibly due to low temp. However, when I switched to liquid injection, I saw large peaks of phthalates (liner was replaced too). The injection port temperature was set at 250C for both headspace and liquid injections. Is there anyway to remove the contamination, besides running multiple solvent blanks? I have been running more than 10 liquid blanks and the peak was still there (10^5 signal, initial signal 10^7). Thank you.

0 paulsalverda 13 days ago

Pthalates can come from a number of sources. Sample, vial, vial cap septum, plastic pipettes, plastic solvent squeeze wash bottles, plastic beakers, and more. Some solvents extract them from some vial cap septa so be careful to never let the sample touch it.

You may need to do full inlet maintenance and cut off 25cm or more of the column again.

One thing to try. Set the inlet to SPLIT. Set the inlet pressure to 1 or 2 psi - as low a pressure as the inlet will maintain. This puts the least amount of flow into the column. Set the split flow to 500 ml/min. With a manual 10µL syringe, pull up a full syringe of clean injection solvent that has never seen any plastic, and slowly inject the syringe full, taking about 8 or 10 seconds to depress the plunger. Do this 8 or 10 times. Then load your normal run method to reset the injection port pressure and flows and do a blank no injection run. This often helps reduce or remove the contamination.
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