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- Posts: 8
- Joined: Wed Jul 21, 2010 8:44 pm
Hi. I was having a problem analyzing extractables from stopper material West 4023/50 with drug placebo. I hope somebody can help me.
The drug placebo contains PEG3350, ala, his, gly and surcose. We are trying to develop a LC/MS method to analyze if there's any extractables in the placebo. I was using a Waters Acquity UPLC coupled with LCT premier XE mass spec. The column is BEH C18 2.1*50mm. MPA is water and MPB is acetonitrile. The gradient is from 10 to 95% B in 19 min and stay at 95% for another 9 min. Then the gradient went back to 10% and re-equilibrate for 4 min. MS detection is W+ and W- mode with a scan range of 150-1500 m/z.
Initial attemp seems OK. PEG shows a big interference but I can still get reproducible result. The Irganox 1010 we spiked in can be detected in both W- mode and UV 215nm. While eveything mess up after I have the entire system, including Column and MS, washed with ACN for a weekend. I start to get suddenly increased background noise. Even for water blank, it shows a lot of peaks. I took off the column and it still shows the high background. So I cleaned the needle and the LC system with mixture of water/MeOH/ACN/IPA with 1% formic acid. And I cleaned the sample cone of the MS and rebuild the capillary. The last time I rerun the sample, I get some unexplained peak from 24 min, especially in negative ion mode. It just seems like something goes wrong when the organic MP start to increase. Even the locksrpay channel intensity increase as well. While the Leu-enk we use for MS correction doesn't increase. It's some background noise less than 500 m/z that show significant increase.
I'm wondering whether somebody can give some thoughts on these. I've been working on this trouble-shooting for a week and get really frustrated. I hope a fresh eye can help. I also have a couple of questions:
1. I noticed for the TOF instrument I used, i loss a lot of sensitivity when alterating between pos and neg ion mode. So I have to run a seperate run for each. Is it true?
2. Is there a problem for using the high organic like 95% of ACN as mobile phase for MS?
3. Is the PEG in the formulation causing instable ionization?
Thanks a lot.
The drug placebo contains PEG3350, ala, his, gly and surcose. We are trying to develop a LC/MS method to analyze if there's any extractables in the placebo. I was using a Waters Acquity UPLC coupled with LCT premier XE mass spec. The column is BEH C18 2.1*50mm. MPA is water and MPB is acetonitrile. The gradient is from 10 to 95% B in 19 min and stay at 95% for another 9 min. Then the gradient went back to 10% and re-equilibrate for 4 min. MS detection is W+ and W- mode with a scan range of 150-1500 m/z.
Initial attemp seems OK. PEG shows a big interference but I can still get reproducible result. The Irganox 1010 we spiked in can be detected in both W- mode and UV 215nm. While eveything mess up after I have the entire system, including Column and MS, washed with ACN for a weekend. I start to get suddenly increased background noise. Even for water blank, it shows a lot of peaks. I took off the column and it still shows the high background. So I cleaned the needle and the LC system with mixture of water/MeOH/ACN/IPA with 1% formic acid. And I cleaned the sample cone of the MS and rebuild the capillary. The last time I rerun the sample, I get some unexplained peak from 24 min, especially in negative ion mode. It just seems like something goes wrong when the organic MP start to increase. Even the locksrpay channel intensity increase as well. While the Leu-enk we use for MS correction doesn't increase. It's some background noise less than 500 m/z that show significant increase.
I'm wondering whether somebody can give some thoughts on these. I've been working on this trouble-shooting for a week and get really frustrated. I hope a fresh eye can help. I also have a couple of questions:
1. I noticed for the TOF instrument I used, i loss a lot of sensitivity when alterating between pos and neg ion mode. So I have to run a seperate run for each. Is it true?
2. Is there a problem for using the high organic like 95% of ACN as mobile phase for MS?
3. Is the PEG in the formulation causing instable ionization?
Thanks a lot.
