by
dhdh » Wed Jul 10, 2013 7:57 pm
Hello everyone,
My company recently purchased PerkinElmer Clarus 680 and SQ 8T GC/MS for this project.
I am seeking to find methods for Pesticide/PCBs/Dioxins and Furans analysis in marine oil using GC/MS by Quechers method.
Currently PerkinElmer chromatography specialist is working on Pesticide method, then he will move on to PCBs and Dioxins/Furans.
I think he is having hard time working on sample extractions on certain types of fish oils (Ethyl Ester forms) and is trying to put this project on delay.
It has already been 4 months since we got the instrument and there is no progress at all.
I have already reviewed USP <561> for pesticides, EPA 1668A and 1613B for PCBS/ Dioxins and Furans analysis, but these methods are too complicated and time-consuming.
I am wondering if anyone can give me some advice regarding this project.
Any help would be appreciated.
Thank you
Well, the QueChErs chemistry was never intended for fatty foods like fish and meat
and dXXXy. There are numerous groups attempting to adapt it beyond fresh fruits and vegetables (groups who can explore it in much greater depth than the quickie "cheat sheet" method application notes from the instrument manufacturers), but I haven't seen anything validated yet in the AOAC Journal or elsewhere. It was surprising they got it to work for the PAH's in fish after the Gulf oil spill...the higher water solubility of PAH's compared to other non-polar hydrocarbons made it squeak by.
The old Mills method in the FDA PAM1 may be just as easy as QuecherS.
If you want to explore that, find the appropriate sections at
http://www.fda.gov/Food/FoodScienceRese ... 111455.htm, specifically Chapter 3, Multiresidue Methods:
http://www.fda.gov/downloads/Food/FoodS ... 111508.pdf
Figure 301-2 shows that fatty foods need extraction method 304.
It's a well established method for whole fish. Most all the non-polar organochlorines get fully extracted this way, including the insecticides, the PCB's and dioxins. Since you have the fish oil already extracted, that saves a lot of work, you can skip 304 E1 or E2 and proceed as in cleanup steps 304 C1 or other.
Basicly, 3 g fish oil is diluted to 15 mL in pet ether, that 15 mL is extracted with 30 mL acetonitrile, then water is added to the acetonitrile and the organochlorines are partitioned back into pet ether, and concentrated down to a few mL. This is needed to remove the triglycerides that don't make it thru a GC column at normal temperatures. (You might even try simply injecting the first acetonitrile extract before the pet ether back extraction, and see if your recoveries are acceptable and the chromatograms aren't too messy.)
It could be miniaturized to where you don't need sep funnels, just the polypropylene centrifuge tubes used in qUechers. Florisil cartridges or other cleanup steps are needed to remove the huge amount of free fatty acids that elute near the DDT's, PCB's, etc.
For what it's worth, I can't suggest anything beyond this! Dan H
p.s. I think it's the "International Fish Oil Standards" organization (or possibly another group) that may have good info for you as far as pre-existing standardized methods. Some of the main concerns of fish oil pills were rancidity as measured by Peroxide Value, PCB's and dioxins by GC-ECD or GC-MS, mercury and other metals, etc. (And of course, DHA and EPA content.)
http://www.ifosprogram.com/industry-home
(UPDATED LATER, WITH A CORRECTION) Well, maybe it works OK for dairy products - the 2X volume acetonitrile does a nice job breaking up the milk lipoprotein complex, causing much of the protein to settle out of solution and releasing the milkfat.
The original question did not indicate the analyst had access to GPC (aka SEC) unit, but that does a nice job of removing the triglycerides (separating higher molecular weight non-polar lipids from the medium molecular weight non-polar pesticides). The downside is that you have to concentrate the collected extract another time, and it consumes more solvent. Very useful for fish, vegetable oils etc, but not necessary for typical fruits and vegetables that have negligible fat content.
