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- Posts: 3
- Joined: Tue Oct 13, 2020 7:08 pm
i have a problem with DMA (dimethylamin) carryover… maybe some of you have a new idea or experience with this problem.
I detect around 54000 area DMA and in the next Blank Vial i found 550 area DMA.
-Same retention time every injection
-carryovers in the next 7 Vials
Method: EP, so its not my own
extra method info.: i inject 10 uL solution in a vial (same with DMA solution and blank)
System:
Perkin Elmer Clarus and Turbomatrix 40. I dont use a trap or something. Just the standard system with pressure time (0,5min), thermostating (10min) and injection time (0,06min)
Column: Stabilwax-DB 30m x 0.53 mm ID, 1.0μm df, Restek
GC: Inlet. 180°C, oven 35°C up to 160°C, detect 220°C, Split 1:1, run time 11min
HS:
Oven Temperature: 60 °C
Needle Temperature: 85 °C
Transfer Temperature: 90 °C
GC Cycle-Time: 15 min
Thermostating Time: 10 min
Pressurization Time: 0,5 min
Inject Time: 0,06 min
I use water as diluent.
ok i tested
-lower concentration
500ppm-carryover 550area, 300ppm-carryover 450area, 100ppm-carryover 320area
higher needle and transferline temp. highest test 125°C needle and 135°C line
- down to 330 area DMA crossover
longer Thermostating Time: longest time 45min
- with temp. change down to 200 area carryover
Ethanol as diluent
-with temp. and time changes down to 100 area DMA carryover
i tested the same with our second GC and the standard carryover is 1300 area instead of 550 area (first GC).
Why thermostating time? Page 186
https://www.perkinelmer.com/lab-solutions/resources/docs/GDE_TurboMatrixHSHSTrapUsersGuide.pdf
During the thermostatting phase (Standby)
the sampling needle is in the upper position. The carrier gas flows
through solenoid valve V1, to the column; at the same time the
needle cylinder is purged by a small cross flow vented through
solenoid valve V2 and needle valve V2. The cross flow prevents
carry over between injections
I have no more ideas….
Thanks for your help
greetings
Marvin