Carryover?

[pstaunton]

Currently working on a method that involves testing liquid formulations for trace level impurities.
Toluene is used in my bracketing standards as a reference for calculating concentration of impurities.
Everything was fine up to a point and then all of a sudden I started to get the toluene peak in my samples. The strange thing is that the peak area of the toluene in the samples is the same as in the standards so clearly this is not a build up of carryover over time.
What could be causing this?

[Peter Apps]

Toluene in the samples would be the simplest explanation, but quite a coincidence that it has the same consentration as the the standards.

Details of what you are doing, and how would help, i.e. temperatures, flows, sample and standard prep and so forth.

Peter