Chromatography Forum

why in the middle of a run of about 100 samples did 10 or so samples suddenly have morphine in them. agilent GCMS machine runs day and night processing opiate confirmations, these samples should not have had morphine but they do, and the boss is not happy

Contamination during sample prep? Glassware?

if the following sample did not have the analute, just repeat samples that had it for confirmation, it could be worth preparing them again as suggested by Rolandas Plausinaitis

the sample prep is liquid liquid, and I oversee all of it, it is quite resistant to swapping etc, someone in my lab also mentioned contaminant, but the amounts were in the 1000 to 1200 ng, now, if the ISTD was the culprit it would have been in all samples because they are extracted en masse, using batch methods, if it was the working standard, no deuterated compund, we use an opiate mix of 7 opioids, so all would have shown, not just morphine, fortunately that mixture isnt even used for the extraction only during calibration. It was safely in the freezer. If it was cross contamination during sample prep, i would have had to splash a lot of one high morphine containing sample over 4 or or 5 test tubes to get 1000 ng or more in the sample. I am sure that didnt happen. We do not reuse glassware. I want to believe that the inlet port, or the wash inlets are filthy, which they usually are, thanks to are stressed work load, and a blob of morphine worked itself loose fropm somewhere and flowed on down the column during the run, is this possible?

More than likely it's trapped in your injection port. What is your solvent? What volumes are you shooting? What liner? If you are overrloading the injection port it could make it into your split vent line.
Agilent has a neat tool ( Hewlett-Packard Flowcalc 2.0) that you can download from their website. You punch in your injector contitions solvent and injection volume and it calculates the vapor volume and whether or not your overloaded.