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Carryover with extended needle seat sample loop

Question asked by poli275 on May 7, 2020
Latest reply on May 11, 2020 by gabcaron

I have a 1290-I system with G4226A, have an 80uL needle seat sample loop installed for injecting 50uL as prescribed by the Pharmacopeia method. 

 

With the sample loop installed, we observed sample carryover, which disappeared after an injection of a blank solution.

 

Carryover is not observed when the sample run is done with 40uL without the sample loop installed, which I assume that my needle cleaning through the flush port is sufficient to remove most contaminants on the outside of the needle.

 

To my understanding, the ferrule of both needle seat capillary and the sample loop capillary are by default fixed at the time of manufacturing, in this case, will it be possible that there exists a small dead volume in either of both junctions that resulted in my observation?

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