PAH BY GC-MS/MS

Hi dear community member. I need your help with the following issue: I am trying to set up a method for analysis of benz(a)pyrene in food by 7890B GC with 7010 QQQ. I use the application note 5994-0553EN as a reference. I have two problems 1) bad area repeatibility when I inject 5,10 or even 20 ng/ml benz(a)pyrene standard in acetone or acetonitrile. 2) There is a carryover after injecting the standard and I need to inject 2 solvent blanks in order to remove this. I checked the repeatibility of the instrument with 0.1 ng/ml (100 fg/mkl) Octafluoronaphthalene (OFN) and it is pretty good, the area RSD of 5 injections is less than 4 %. So I guess it is related with the method. I use the 30 m DB-35MS column with 2 ml/min flow, 2 mkl splitless injection with 50 ml/min purge flow at 1,5 min. MMI inlet temperature is 280 deg C. liner is 5190-2293 with glass wool. Oven program 1 min at 80 deg C, heat to 200 deg C with rate 25C/min, then heat to 305 deg C with 8 C/min rate. Transferline temp is 320 deg C. both quads are at 150 deg C, source at 230 deg C. Quantifier MRM for benzapyrene is 252.1>>252.1 (CE 10, dwell 50 ms), qualifier is 252.1>>250.1 (CE 10, dwell 50 ms). Does anybody has idea what could be the reason?

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