Chromatography Forum

Hi, we are using an Agilent 1200 coupled to a Applied Biosystems 3200 MS/MS for opiate analysis. Since mid December 2007 we have started having trouble with large fentanyl and methadone peaks in blanks and even with zero injection volumes. We usually flush the system with 95% acetonitrile to get rid of this but now this no longer clears the carry over. We have replaced the column, gaurd cartridge, sampling and column switching valves and flushed the system for several hours with 30% HNO3 and then with 95% acetonitrile, the peaks still persist.
What is the best method for washing opiates from the system? Any help greatly appreciated.

A few days ago I posted under "Ghost Peak" my 1100 issue with an unknown peak, turned out that a replace autosampler needle seat fix that, had some kind of contamination. I didn't even try to sonicate the older needle seat. I had previously swapped out the autosampler rotor seal and the metering piston seal (since the peak was reproducible, and thus tied to the injection cycle) but those didn't help. So maybe swap out the needle seat. The tubing and needle insides get continually flushed, so I didn't bother with those.

A few days ago I posted under "Ghost Peak" my 1100 issue with an unknown peak, turned out that a replace autosampler needle seat fix that, had some kind of contamination. I didn't even try to sonicate the older needle seat. I had previously swapped out the autosampler rotor seal and the metering piston seal (since the peak was reproducible, and thus tied to the injection cycle) but those didn't help. So maybe swap out the needle seat. The tubing and needle insides get continually flushed, so I didn't bother with those.

Hi, thanks for the reply. I actually forgot to mention that the needle seat was the first thing we replaced with no change, Any other ideas?