wanted pure pentane solvent free from halocarbons

[rajdeeproy]

Dear all

i wanted to know is there any grade of pentane which is relatively free from halocarbons such as chloroform and carbontetrachloride. The pentane which i use now is from sigman but it still conatins these two artifacts and i have to distilled it once more before using it. But keeping for longer time do tend to observe this coumpounds from atm.

please give me some suggestion

[chromatographer1]

Many producers of high quality solvents may package the solvents in the same building and it is not uncommon to cross contaminate solvents to a degree which may interfere with an analysis. You have noticed that in your lab the pentane may require additional purification after being opened to the atmosphere. The same happens in packaging.

I recall once having to search the entire campus at Lederle for a single bottle of alkane that did not have an interference with a specific analyte. And I only found one bottle!

The best prevention is to redistill any solvent yourself. While you may receive a bottle of solvent from one vendor without any interferences one time, you can never be certain the next time will be the same.

And of course if you find the one bottle of the 'good stuff', guard it with your life.

best wishes,

Rod

[skunked_once]

Back when I used to do trihalomethane analysis I was able to obtain a special grade of pentane specifically purified for THM analysis from one of the well-known solvent vendors. Sorry, but I don't remember which vendor so you will have to check around. I do remember that once the bottle was opened, it was very difficult to prevent contamination in the pentane in the open bottle. The best practice is to buy small bottles and keep them well away from any possible sources of contamination.

[Bruce Hamilton]

Dear all

i wanted to know is there any grade of pentane which is relatively free from halocarbons such as chloroform and carbontetrachloride. please give me some suggestion

Merck offer n-pentane for organic trace analysis. catalogue number 107288. They are a global supplier, so you should be able to obtain it, if it's suitable.

Bruce Hamilton

[rajdeeproy]

Dear Bruce and all

I heard solvents supplied by british drug house is free from contaminents. If anybody has any such experience please tell me.

best regards
rajdeep

[PJ8]

I've never had a contamination problem with Fisher Scientific high grade solvent, but then I've never had cause to use pentane.

On a similar topic I am trying to develop a method to determine levels of DMSO, DMF is a suitable solvent with the exception that there is a DMSO peak in the blank. Is this common for DMF, does anyone have a manufacturer/grade reccomendation? Maybe just using a fresh bottle and keeping it seperate from the DMSO will solve the problem...

[chromatographer1]

In similar fashion to my previous post, packaging cross contamination at the ppb levels is not unknown. Accidental cross contamination happens when the same bottling line doesn't get completely clean before the next solvent is packaged. Just a tiny film of residual solvent can contaminate the first few bottles of the next solvent, especially the greasy and hard to remove DMSO and DMF products. I recall several years ago that methanol from one vendor was contaminated with less than 1ppm of methylamine from an accidental cross contamination with DMF.

Manufacturers try to avoid this but accidents do happen.

The best defense is to redistill for critical applications.

In your case handling may be the cause of the cross contamination after the bottles were opened, ....... or perhaps not. It is not easy to find the source sometimes.

best wishes,

Rod

[HW Mueller]

Rod, you just gave me a possible explanation of what might have happened a few years ago in HPLC of ouabaine: It reacted with one batch of MeOH on column. I am still mad as the manufacturer didn´t bother to answer questions. An aquaintance of mine tried to find formaldehyde in that MeOH with GC, didn´t find any, so we more or less ruled that out.

[Bruce Hamilton]

I heard solvents supplied by british drug house is free from contaminents. If anybody has any such experience please tell me.

Ok. I recommnded a Merck product. Sorry for the history below, but I believe BDH chemicals are no longer from Merck.

Merck purchased British Drug House reagents about 1973, and for a period until 1990, many of the BDH chemicals were rebranded Merck products ( obvious from the lot number codes).

In 2000, Merck set up VWR to perform distribution of Merck and BDH products, and a couple of years later separated the BDH brand and in 2004 sold it and VWR to an American invester firm, which is now selling BDH chemical products that are sourced from suppliers other than Merck.

My suspicion would be that the BDH products people talk about probably originated from Merck, unless later than 2004. This is only based on my understanding in our market, and timelines and names maybe different elsewhere.

If I have a choice ( very rare ), I would usually purchase Merck, followed by either Romil or Fisher, but it depends on what's easily available in your market. I have no experience of the new BDH chemical products.

I hope this isn't too confusing, but any n-pentane rated for trace organic analyses from Merck, Romil, or Fisher should be suitable.

Good luck,

Bruce Hamilton