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- Posts: 1
- Joined: Thu Jun 07, 2012 4:19 pm
I'm interested in the kinetics of permanganate oxidation of this compound
1) cis-stilbenedicarboxylic acid (CAS No. 133005-88-6)
Which generates the following products
2) terephthalic acid (CAS No. 100-21-0)
3) 4-carboxybenzaldehyde (CAS No. 619-66-9)
I use hydroxylamine as a reaction quencher, which converts compound 3 into the oxime
4) 4-carboxybenzaldehyde oxime (CAS No. 3477-83-8)
I also think benzoic acid will work as an internal standard
5) benzoic acid (CAS No. 65-85-0)
I am using an Alliance triple-quadrupole LC/MS/MS system, with a μBondapak C18 3.9x300 mm column, mobile phase isocratic 0.2% acetic acid (45%) methanol (55%). I run at 1 mL/min and use a flow splitter to send 20% to the MS detector and 80% to a UV detector. Under these conditions compound 1 is well retained and I get good results for it. Compounds, 2, 3, 4, and 5 all coelute, earlier than compound 1. Using the MS detector, I can tell them apart. With just LC/MS I wasn't able to get good calibration curves, but I did (once) using multiple reaction monitoring mode. I realize that these compounds are eluting early because the methanol percentage is so high. However, I haven't been able to get them to separate out at lower methanol concentrations: they just take longer to coelute.
Unfortunately, we don't own many other columns that I can try. We have an Atlantis T3 4.6 x 250 mm column that I have also tried, but I don't get good peak shape or separation for these compounds. Another challange is that none of these compounds are highly soluble in acidic pH. I use 10 micromolar compound 1 at the start of the reaction and am hoping to monitor the generation of the products. The detection limit for compound 1 seems to be in the 100 nanomolar range.
I haven't been able to get a calibration curve to work for 2, 3, and 4 to work in my past few tries. I am hoping there's a way to get the peaks to resolve. Having them coelute is not a very "robust" method.
I'd appreciate any advice you might be able to offer!
Thanks in advance!
1) cis-stilbenedicarboxylic acid (CAS No. 133005-88-6)
Which generates the following products
2) terephthalic acid (CAS No. 100-21-0)
3) 4-carboxybenzaldehyde (CAS No. 619-66-9)
I use hydroxylamine as a reaction quencher, which converts compound 3 into the oxime
4) 4-carboxybenzaldehyde oxime (CAS No. 3477-83-8)
I also think benzoic acid will work as an internal standard
5) benzoic acid (CAS No. 65-85-0)
I am using an Alliance triple-quadrupole LC/MS/MS system, with a μBondapak C18 3.9x300 mm column, mobile phase isocratic 0.2% acetic acid (45%) methanol (55%). I run at 1 mL/min and use a flow splitter to send 20% to the MS detector and 80% to a UV detector. Under these conditions compound 1 is well retained and I get good results for it. Compounds, 2, 3, 4, and 5 all coelute, earlier than compound 1. Using the MS detector, I can tell them apart. With just LC/MS I wasn't able to get good calibration curves, but I did (once) using multiple reaction monitoring mode. I realize that these compounds are eluting early because the methanol percentage is so high. However, I haven't been able to get them to separate out at lower methanol concentrations: they just take longer to coelute.
Unfortunately, we don't own many other columns that I can try. We have an Atlantis T3 4.6 x 250 mm column that I have also tried, but I don't get good peak shape or separation for these compounds. Another challange is that none of these compounds are highly soluble in acidic pH. I use 10 micromolar compound 1 at the start of the reaction and am hoping to monitor the generation of the products. The detection limit for compound 1 seems to be in the 100 nanomolar range.
I haven't been able to get a calibration curve to work for 2, 3, and 4 to work in my past few tries. I am hoping there's a way to get the peaks to resolve. Having them coelute is not a very "robust" method.
I'd appreciate any advice you might be able to offer!
Thanks in advance!
