Hi,
During developement of GC-FID ALS method for quantification of Methanol, IPA, ACN, DCM and DMF I am observing blank interference in methanol, IPA and ACN peak due to DMSO (I came to know its DMSO after doing truobleshooting). I am using DB-624 (75m, 0.530mm, 3.2 um ) column with flow of 2.5 mL/min, my inlet temp is 170 degree celcius and detector temperature is 280 degree celcius. Split ratio is 1:4. I have used different make DMSO but none helped me. Kindly note my sample has solubility in only DMSO so i can not move to different diluent. Please help me.
Regards Ankit
As you are getting blank peak of lower boiler compounds, so you can heat the diluent slightly below 80°C for some time or degass it.
Tabrez Shaikh I have done following excersiz and got following results:
1. Two DMSO blank injected after sonication for 20 min keeping all my parameters as it is. As a result my first blank was somewhat good as the response of both the ACN and Methanol peaks reduced. But then in second blank injection the methanol and ACN peak response increased.
2. DMSO hated at 85 degree for 30 min , allowed to cool to room temperature and the two blank injected. Suprisingly the response of both peaks is same as previous injetions. (No reduction in response)
Please note the injection volume is 1 uL.
Thanks and Regards
Ankit
I would try raising your inlet temp. Dmso has a much higher boiling point than methanol or IPA.
Like Michael Eger wrote before, 85°C as inlet temperature (split-injector) for DMSO as solvent is far to low. The boiling point of DMSO is at 189°C and nomally best results you get to set the injector temperature for split-injection 20°C lower than the boiling-Point of the solvent about 170°C. This is different to on-column injection where you can work at some lower temperature. In split-injection you should evaporize your sample in seconds or your split will seperate different compounds with time or in wrost case the liquid will pass your injector without epaporating.
Michael Eger , Manfred Elend
Thank you for your response. Please note my inlet temperature is 170°C only (Please refer my original question for other chromatographic parameters).
Tabrez Shaikh has suggested me to heat/sonicate the diluent at 85°C before going to analysis as my interference has low boiling point solvent (the idea behind heating the DMSO at 85°C to evaporate ACN, MeOH and IPA from DMSO), but heating and sonication did not reduce the response in blank peaks.
Please let me know if there is any other way to solve this.
Regards
Ankit
I would still raise the inlet temp. Try 175, then 180.
Also what is rest of program? What is the RT of the solvents. Maybe even try a pulsed split on the inlet. What type of inlet? Standard split/splitless, MMI.
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