mobile phase stability

[rick1112]

Hi

Could any one let me know what is the stability of mobile phases- water + 0.1% TFA and ACN + 0.1% TFA? I mean how long after the preparation of these mobile phases I can use them without any significant variation in analysis??
Is there any storage condition for these mobile phases?

Thanks a lot

[Jackus]

We use such phases for one month.

My general recommendation:
-phases highly volatile: 1 day at lab temperature, 1 week in refrigerator
-water based phases w/o buffer: 1 month at lab temperature
-buffered phases with pH <4: 1 month
-buffered phases with pH >4: 1 week

I was present when auditor asks us if we had tested expiration of mobile phases during validation. We were startled till he started to laugh and told that if we have any report, it is the first instance when it is done.

[rick1112]

do anyone do keep track of the performance of mobile phase (in terms of resolution, noise ,drift, etc )
plz let me know if anyone has such a in-house data?

[DR]

We use such phases for one month.

My general recommendation:
-phases highly volatile: 1 day at lab temperature, 1 week in refrigerator
-water based phases w/o buffer: 1 month at lab temperature
-buffered phases with pH <4: 1 month
-buffered phases with pH >4: 1 week

I was present when auditor asks us if we had tested expiration of mobile phases during validation. We were startled till he started to laugh and told that if we have any report, it is the first instance when it is done.

I'd have replied by asking to see the validation report for his auditing procedures. [/hijack]

We generally allow a month for mobile phases except for those that are buffered and less than 5% organic - they get 1 week (or until fuzzy, which ever comes first).

[juddc]

I'm neurotic - nothing more than 3-5 days on the system regardless of what it is, ever.

Pure solvents that I've removed from the LC reservoirs usually end up being used for sample preparation so they're not wasted. Mixed MP's are made up sparingly.

Any reservoir and solvent line that can incur growth is rinsed with DI water (if a buffer is present) then neat methanol periodically - every 1-2 weeks as a matter of course.

Any reservoir that has plain unbuffered water used is replaced daily and rinsed with methanol weekly.

I don't want the age of my MP to ever be a factor in any separation.

[Bruce Hamilton]

One obvious answer is to point to the shelf life of the preformulated 0.1% TFA mobile phases that you can buy.

For methods that are going to be used frequently for a long time ( months, years ) I tend to check the same standards on both new and older batches of solvents, and that confirms the solvent shelf life.

I suspect shelf life is defined by clean containers, good solvent changing habits, and ensuring minimal loss of volatility or air ingress during use and storage.

Some methods might be more susceptible to mobile phase changes than others. I've had methods where the 0.1% TFA in both water and acetonitrile was OK after 6 months, but I didn't test longer than that.

Bruce Hamilton

[shaun78]

A long long time ago when I was working for a major pharma company, the company decided that they wanted the validations group to evaluate the stability of mobile phase within a reasonable amount of time.

One of the mobile phases that we went literally hog wild with was 0.1% TFA in water/acn. Solvnet was stored in bottles when not attached to LC. Clearly, we were not concerned about growth in the organic; but were a little cautious of the water.

We drug that study out for six months.

After six months neither solvent showed any microbial growth. After six months, the data generated using the mobile phase matched exactly with the data generated six months previous.

[syx]

Hi
Could any one let me know what is the stability of mobile phases- water + 0.1% TFA and ACN + 0.1% TFA? I mean how long after the preparation of these mobile phases I can use them without any significant variation in analysis??
Is there any storage condition for these mobile phases?
Thanks a lot

0.1% TFA in water: freshly prepared. I never save any aqueous solution to avoid microbila growth.
0.1% TFA in acetonitrile: we save it up to 6 months in room temperature (refrigerated is better). It is better to try the reproducibility between old and new mobile phase.