hi good morning everyone
we are doing 3 MCPD analysis by AOCS official method Cd 29c-13. in this method three standards mansion for 3 MCPD.
1. d5-3-MCPD-1,2-bis-palmitoylester
2. 3-MCPD-1,2-bis-palmitoylester
3. 3-MCPD,99%
but in procedure mansion only standard 1. so my question is we can use only any one std or all three std use compulsory??
i believe that standard 1 is an internal standard for 3-MCPD (2) to correct for matrix suppression of the native 3-MCPD (no 2). You need both of them to accurately quantify the analyte. Both will have the same retention time and will be suppress (in LC/MS) at the same manner. Standard no 3 is different in structure and may have different retention time.
Thank you Narong Chamkasem Sir,
we are developing AOCS 29c-13 by GC-MS Instrument but your answer is regarding LC-MS. so we can use only 1 std or both std require for GC-MS???
if, both std require then how much concentration require for sample extraction?
You have to understand that the matrix effect on analyte response occurs at different places for LC/MS vs GC/MS. For LC/MS, it is matrix suppression at the ion- source after the column separation, so you need to have the IS with "exact" retention time so both native and IS are suppressed at the same degree and cancel out the matrix effect. Therefore, you need IS for each analyte if they are eluted at different RT. On the other hand, matrix enhancement on GC occurs at the hot splitless injector port where the liquid sample is vaporized at the "same" time and the analytes are then separate on the column. Matrix enhancement occurs because matrix will protect analyte from degradation at hot injector port vs standard in solvent. I would assume that all analyte "may" degrade at the same rate or as not critical at the hot injector port. So, for GC/MS, you may be able to use "one" IS for both analyte. In pesticide analysis by GC/MS, we use three IS to correct for 200 compounds. No matter what I told you, you still have to test it experimentally.
Good Luck
Narong
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