Chromatography Forum

Is it ok to put NaN3 (bacteria deterent) in 20% methanol or 20% ethanol solution? I usually don't but was wondering if I can.

S

Dear Friend,

I see no problem adding NaN3 to your mixture, but I do not see much reason to do it. The alcohol % you describe would normally be enough to prevent bacterial growth by itself.

If you want to add it in any case, just remember that the Uv transparency will change drastically. Even at ppm levels, NaN3 will be totally non-transparent below 280nm.

Good Luck,

josebenjamin

Hi,

I thought the alcohol would do the trick for warding off bacteria but thought that perhaps with such a low concentration, there may be a need to add NaN3. Anyway, I had been wondering this...thanks for replying.

S

what column are you using?

some columns used for sugars/carbohydrates cannot be stored with organics, so best to use the sodium azide.

Greetings from a first poster!

An application I developed makes use of an isocratic mobile phase 95%A/5% B, using the instrument's GPV to combine A and B:

where:

A = 20mM Acetate buffer pH 5.1
B = ACN

This being an ideal pH range for microbial growth, I've observed the shelf-life of the buffer to be <5 days, so I'm interested in stabilizing this buffer if possible. Keeping in mind that UV detection is @ 214/230 nm, my questions are:



1) What would be an effective (minimal) concentration of NaN3 to prevent microbial growth in this buffer?

and

B) Would it be opaque under the stated conditions?

Thanks in advance...

5% ACN should be enough to ward off bacteria. Premix your mobile phase. It will be good for at least a month. You will probably also see a bit smoother baseline.

Azides are not good for HPLCs.

what column are you using?

some columns used for sugars/carbohydrates cannot be stored with organics, so best to use the sodium azide.

I do not recommend using azides as preservatives for carbohydrate columns especially if they contain heavy metals like lead or silver.
Our Hamilton carbohydrate columns can tolerate water/organic solvent mixtures (like 80%water/20%acetonitrile) that can be safely used as storage medium and I guess this is similar with other manufacturers. So check with them first.

Robert

5% ACN should be enough to ward off bacteria. Premix your mobile phase. It will be good for at least a month. You will probably also see a bit smoother baseline.

Azides are not good for HPLCs.

I would have thought that 5% organic wouldn't be enough, but premixing's certainly worth a try. I'll report back later.

Many thanks again for your reply.

Agree with DR. Sometimes have problems with bacterial growth in aqueous samples and methanol seems to enhance it. bacteria are not happy in the prescence of ACN, add some.

Bear in mind that while relatively low (a few %) levels of organic solvent are at least bacteriostatic, there is the possibility of selective breeding. If you have even a few survivors that tolerate a particular organic solvent, after generations, you will have a population of bugs that love the stuff.

I learned this the hard way years ago comparing notes in two labs, one using phthalate and another using p-hydroxybenzoate buffer for ion chromatography.

But one would think that one needs to be quite clever to carry the survivors from one prep, etc., to the next.

But one would think that one needs to be quite clever to carry the survivors from one prep, etc., to the next.

They are "clever" enough to accomplish that all on their own. Just consider the increasing prevalence of antibiotic-resistant germs as a parallel.

I was once on a service call where the complaint was a flat chromatogram for an OPA/fluorescence method. It seems that the detector was overloading. The cause turned out to be a vigorous bacterial colony in their phosphate buffer. It looked someone had coughed up a wad of mucus in there. I suggested they take the whole HPLC system over to the bacteriology department and autoclave it. I never heard from them again.

Tom, the antibiotic resistant microbes have also been created by extraordinarily gifted individuals (human individuals). Feeling better, thus cutting the medication, or even more efficient: there are whole countries in which it has become fashion to pop in a pill of antibiotic when the toe hurts (fashionable shoes) or gas got stuck....

Dear Mark,

Is there anyway to know if there are bacteria in our columns/HPLCs?