Parafin Wax in Sterile 10ml Syringes

Discussions about sample preparation: extraction, cleanup, derivatization, etc.

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We have been working on 525.3 semivolatile drinking water methods and to simplify the drying step we tried making drying tubes using sodium sulfate packed into 10ml Syringe barrels. Early attempts looked promising, but our last few tries we had massive contamination of heavy hydrocarbons at the end of the analytical runs, the peaks and hump double or even up to 10x the height of the internal standards spiked at 1ppm. After testing every component one at a time we finally found it was the syringes.

Has anyone ever seen something like this, and is it normal for a sterile BD 10ml luer sliptip syringe to contain parafin wax? These are approved for injections into humans, so would that be considered safe?

We will probably be looking at either small SPE resivouir to use as drying cartridges or buying prepacked ones, or even possibly the 50ml DryDisk from Horizon. Does anyone have experience with using something like this for drying extracts before concentration?
The past is there to guide us into the future, not to dwell in.
James_Ball wrote:
...Has anyone ever seen something like this, and is it normal for a sterile BD 10ml luer sliptip syringe to contain parafin wax? These are approved for injections into humans, so would that be considered safe?
...

I guess they were 3-part syringes (with black elastomer on the piston).
You may try 2-part syringes. They should be better
Hi James

I have had bad experiences with samples taken into what medics and vets think are clean containers. Medical equipment has to be sterile and free of harmful contaminants - that does not mean that it has to be anywhere near what an analytical chemist would consider to be clean. Sometimes it will be clean, sometimes it will have contaminants that mess up some analyses and not others. How clean it is (for a chemist) can vary from batch to batch of the same product. The medics' approach to chemical contaminants is about the same as a chemist's approach to microbes - which medics view as incomprehensibly sloppy.

Empty SPE tubes can be expected to be consistently chemically clean, because chemistry is what they are made for. Rather than SPE tubes I use glass Pasteur pipettes for SPE etc because I can super clean them by baking them.

Peter
Peter Apps
dblux_ wrote:
I guess they were 3-part syringes (with black elastomer on the piston).

You may try 2-part syringes. They should be better


Decades ago, when we used disposable syringes for filtering samples, we bought some without any rubber/plastic seal on the piston. I can't remember the brand name right now, but they were made in Europe, so Google.
For filtration of LC samples we use these syringes: https://www.ddbiolab.com/frontoffice/pr ... d=0K-03-01

available at a lot of vendors, I just picked one that had a photo of the product.
Yesterday I did check one of the two part syringes without the black rubber plunger and they were much cleaner, but instead of what looks like heavy hydrocarbons or paraffin wax, they are contaminated with heavy amides, major masses of 59 and 72. After looking at the masses from the first syringes with full scan I am beginning to think that it is silicon oil instead of paraffin because the major masses are 73, 207, 281 and 96.

I was doing 525.3, 530 and 541 for UCMR4 back in the summer and the syringes worked fine for the drying step, now I can't even see the internal standards on a SIM run. I will probably just order some of the 10ml SPE reservoir tubes to make cartridges, although I found that UCT has some 5g ones for less than $4 each. Has anyone here had any experience with the DryDisks from Horizon? I have seen those demonstrated but not sure if they are super clean and how expensive they would be.

I have used the pasteur pipettes before for small scale cleanup, but I need 4-5g of sodium sulfate to remove all of the moisture from the extracts so I don't think I can get any large enough for this project. They are perfect though to make a silica gel column for 1ml extract cleanup for waste waters though.
The past is there to guide us into the future, not to dwell in.
Dry disks from Horizon work great if you are using a solvent that is heavier than water. They are also a tad pricey compared to sodium sulfate.

If you are using a light solvent, use borosilicate sintered glass drying tubes and muffle at 450 C between uses.
Don Shelly
LGC Standards
Thanks Don.

I did notice they are a little expensive but the Drydisk Barrels (mounted in 50ml disposable tubes) are about half way between the price of the 5g sodium sulfate tubes from UCT and the 2g ones from Restek, so those are within the range of being affordable.

I am looking to use them for 525.3, with the MeCL/Ethyl Acetate mixture, would the drydisks work for that? Also one of the UCMR methods uses Methanol/MeCL which I don't think would work at all.
The past is there to guide us into the future, not to dwell in.
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