QA on Incoming Solvent (LPG)

All,

I am curious how you all QA/QC your incoming LPG. I have had two occasions where I was provided tainted solvents by two different LPG suppliers. And yes they were big name providers and still fucked it up.

Once I was sent Propane that had mercaptans in it, that was marked exactly like a lab grade tank, and completely fucked up a ton of extract because I didn’t smell it until I had already transferred it into my holding tank and started a run before I disconnected it.

The second time I received a propane tank that ended up somehow having benzene in it and this time didn’t find out until we tested the material at a lab. Now we are trying to figure out what else could have potentially been contaminated by that tank. Big pain in the ass.

Anyways my question is whether any of you have developed a QA procedure for incoming solvents so that you don’t have to fuck up a bunch of material before you figure out that it is in fact tainted. I’m not exactly trying to open up and smell every tank we receive and I’m hoping there is more of a low cost detector or something I could use.

Thanks for all your help as always,
-Butane

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Did you try searching benzine? There was a thread about benzene in major gas suppliers stuff… Willing to bet this has been discussed in depth there

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@HuartzBanger beat me to it, you should search Benzene here, there have been a few discussion threads on some tainted gas that was in supply.

Personally, we’ve been looking at measuring utilities in-line to provide live read out of what’s in the solvent as it flows into the tank. Some manufacturers have been helpful in helping us with the endeavor, but still in R&D.

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Benzene is purgable in a vac oven.

We added an activated carbon filtration onto our system after the mol sieve which should help clean gas in the future.

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Plenty of discussion on the problem, didn’t notice much in the way of end user solutions…

@Butane is correct that performing QC on the incoming gas is the correct response. The question is, what tooling is required?!?

@srihugh1 might have some insight. As might some of the vendors in the benzene thread(s) you’re referencing.

GC-FID with a hayesep D/R column might work…

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A quick google search for “draeger tubes mercaptan” brought back this result. I think I’ve seen on here that some people have used them in the industry for various purposes. At $9 a piece for a $400-700 tank of gas seems reasonable.

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My procedure goes as follows:

Take a gram of extract, or whatever your testing labs needs to proform residual solvent analysis.

Mix the gram with solvent straight out of the tanks from the distributor. If you receive more than one tank at time then add solvent from every tank to the single gram to save on testing costs.

Safely evaporate the solvent and send the sample in for solvent analysis before you ever introduce the dirty gas to your system.

As far as mercaptans go you can use activated charcoal or 13x mol sieve beads in the vapor path while distilling. I use it everytime for preventative maintenance.

If you use charcoal, use it in line before some 3a/4a ms beads. The charcoal will add water to your gas.

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A 15 meter capillary column like the 15MXT1 5micron film would be my choice to best measure benzene because the peak is sharper and thus easier to detect at low levels. A 1 ml injection should be able to detect benzene at 1 ppm.
We have a device called a preconcentrator which when added to the GC enables detection of benzine at ppb levels.

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