GC-QQQ contamination problem

[Rocknroll99]

Thanks for the info, Will look into it.

Funny thing is if we inject air we get a flat base line, so my guess it is not coming form the system (or gasses)

Scratching what's left of my hair...

[Rocknroll99]

For anyone who has this problem, we found the contaminations coming from the syringe. Any syringe replacement on the third injection after replacement the DIPN would go through the roof and take a long time to come back down.

We are working with Agilent to find a suitable syringe. (working remotely so can tell you the syringe we used)

[James_Ball]

Are you using syringes with the teflon tip or just the all metal plunger?

Just wondering if it could be a teflon artifact.

[Rocknroll99]

I am writing to let anyone who has this issue know that we have solved the DIPN contamination issue on our Agilent by avoiding the gold standard syringe (5181-3360) and using the blue line syringe (G4513-80203) which doesn’t have the contamination issue.

I’ve put some data in below which shows at the beginning of the batch where the gold line syringe is being used that the contamination starts off low but gets progressively worse with each injection and completely swamps the 0.004 and 0.02 µg/mL standards.

Mid-batch we swapped in the blue line syringe and the DIPN level immediately dropped to a manageable level and was no different from noise by the 3rd injection. We then ran some calibration samples and followed by blank injections and everything worked well with no carryover detected except for the first two injections when the syringe was first installed.

These samples are made up in hexane and the method has a pre-wash with hexane and a post wash with DCM.
A summary of our data is below (blue line syringe samples are highlighted), and a link to the batch is lower down if you want to look at it for your own reference. Just be aware that the sequence mixes up the 0.004 and the 0.02 µg/mL standards.

Name Acq. Date-Time Resp.
221005 hexane1 Std needle 1 05/10/2022 13:40 2528
221005 hexane1 Std needle 2 05/10/2022 14:04 9749
221005 hexane1 Std needle 3 05/10/2022 14:28 12695
221005 hexane1 Std needle 4 05/10/2022 14:52 26793
221005 hexane1 Std needle 5 05/10/2022 15:16 19574
221005 0_02ug_mL Std 1 05/10/2022 15:39 67577
221005 0_004ug_mL Std 1 05/10/2022 16:03 51289
221005 hexane2 blueline neede 1 05/10/2022 16:27 202
221005 hexane2 blueline neede 2 05/10/2022 16:51 389
221005 hexane2 blueline neede 3 05/10/2022 17:15 111
221005 hexane2 blueline neede 4 05/10/2022 17:39 187
221005 hexane2 blueline neede 5 05/10/2022 18:02 67
221005 hexane2 blueline neede 6 05/10/2022 18:26 68
221005 0_004ug_mL Std blueline 1 05/10/2022 18:50 35033
221005 0_02ug_mL Std blueline 1 05/10/2022 19:14 6936
221005 0_004ug_mL Std blueline 2 05/10/2022 19:38 33484
221005 0_02ug_mL Std blueline 2 05/10/2022 20:02 6610
221005 0_004ug_mL Std blueline 3 05/10/2022 20:26 34700
221005 0_02ug_mL Std blueline 4 05/10/2022 20:49 6749
221005 0_01ug_mL Std blueline 1 05/10/2022 21:13 16988
221005 0_2ug_mL Std blueline 1 05/10/2022 21:37 355283
221005 0_004ug_mL Std blueline 4 05/10/2022 22:01 32901
221005 0_004ug_mL Std blueline 5 05/10/2022 22:25 32284
221005 0_004ug_mL Std blueline 6 05/10/2022 22:48 32733
221005 hexane2 blueline neede 7 05/10/2022 23:12 58
221005 hexane2 blueline neede 8 05/10/2022 23:36 78
221005 hexane2 blueline neede 9 06/10/2022 00:00 54
221005 hexane2 blueline neede 10 06/10/2022 00:24 13
221005 hexane2 blueline neede 11 06/10/2022 00:47 46
221005 hexane2 blueline neede 12 06/10/2022 01:11 42