By Anonymous on Friday, April 4, 2003 - 09:59 am:
Hi,Everyone:
I recently work on a vegitable oil analysis. It is a complicated triglyceride mixture, hardly to tell how many compounds are in there.
I found a USP method for a similar compound, which uses 60/40 ACN/Mecl2 as mobile phase on C18 column, I tried it, peaks coming out right after column void and continue beyond 50min., which indicates some compounds are very retentive on C18 column.
Another literature method uses a mobile phase of ACN/0.1% Acetic acid in water 70/30 on C18 column, the author claimed all peaks are eluted in a time span from 8 to 30 min.
Column dimension and flowrate conditions are identical in both methods. There is no gradient elution involved in either method.
Based on the resluts from 1st method, I just cann't believe what it was said in the second method. I think most compounds should have remained on the column in the second method.
Anyone can give me his explanation on this topic?
Thanks
Another
By Anonymous on Friday, April 4, 2003 - 12:02 pm:
You really didn't ask this, but we've used 85% HPLC grade ethanol (which itself contains 90% ethanol, 5% methanol, and 5% IPA) and 15% acetonitrile for triglycerides on RP-18.
By Anonymous on Friday, April 4, 2003 - 03:40 pm:
C18 columns are not alike, but I do have some doubts that both methods do the same thing. What are the columns used by both investigators?
By Fabiano on Thursday, April 10, 2003 - 04:07 am:
ACN/H2O will not elute a complex TG mixture like soy oil,here we used C18 250X4.6mm with ACN/IPA/Hexane 60/15/25 , the OOO elute in 30 minutes, identification is done by ECN.
By C.Sychov on Thursday, April 24, 2003 - 05:04 am:
For "ethanol" anonymous)): thank you, i`ll try it.
For Fabiano: hexane in RP eluent leads to irreproduceble retention.
I tried AcN-IPA-water 70-30-5, but two peaks I guess LLL and LLO were not separated to baseline on Zorbax SB C8. I think I`ll try C18 phase and higher content of IPA or THF.
If you are interested in results I`ll show when I`ll get them))). It`s a pitty but I have no standards -- Russia and so on)))).
COnstantine
By B.Buglio on Thursday, April 24, 2003 - 06:09 pm:
The first case mobile phase is NARP. The second
case mp is traditional RP so there may well be a
substantial difference if the elution pattern.
Best to verify retention patterns w some stds.