Chromatography Forum

nellermann:

I first became aware of the ACN shortage back in the fall and have since adapted my separation methods. I was running gradients of ACN/TFA with TFA/Water, and now I'm running straight IPA vs TFA/Water. Since have conditions have changed, so have my retention times, but I'm still getting decent separations.

Why did you select IPA over Methanol?

Also, has anyone tried going to 3.0 mm ID columns? If so, was it very difficult?

Thanks

For me, it was just trial and error. I had already tried running methanol to no avail, but the IPA/TFA gradient worked. Admittedly, though, I'm running on experimental columns and performing protein separations.

Why did you select IPA over Methanol?

Also, has anyone tried going to 3.0 mm ID columns? If so, was it very difficult?

Thanks

Hi Paladin - the data (TI475E) I posted earlier gives some information on this.
Assuming column length is kept the same:

Cross sectional area of cylander = pi(r^2) = pi[(0.5d)^2]
For 4.6mm: Area = pi[0.5x0.46cm)^2] ~ 0.166 cm^2
For 3mm: Area = pi[0.5x0.3cm)^2] ~ 0.071 cm^2

Ratio of c.s. area for 3mm/4.6mm = 0.071/0.166 ~ 0.43

So, if flow rate is 1mL/min (on 4.6mm I.D.), new flow rate should
be reduced proportionally to 0.43 mL/min.

Extra column volume effects may need to be considered.
And you may need to reduce inj. volume by 1/2

Note also that if you have to reduce the injection volume by half, this is not a disadvantage! Since many detectors measure concentration, not amount (e.g. PDA/UV and ESI-MS), the concentration remains the same when you halve the injection, so sensitivity is unaffected. In fact, if your injection volume was limited by the sample loop, or the available volume of sample, and not by the column, reducing column diameter can increase sensitivity.

sorry, reading that I realise I didn't make myself very clear: Halving the injection volume while simultaneously reducing the column diameter maintains the same signal; reducing column diameter while maintaining a big injection increases signal.

Why did you select IPA over Methanol?

Also, has anyone tried going to 3.0 mm ID columns? If so, was it very difficult?

Thanks

We went to narrower-bore columns in the mid-1990s. Works great.
Keeping same linear velocity, going from 4.6 to 3.0 saves half the solvent (e.g. flow rate from 1.00 to 0.500).

Going to 2.1mm i.d. saves about 75% the solvent. You may need to halve the injection size.

In general, differences between different C18 columns are smaller than differences between acetonitrile and other solvent options.

One way to get around a solvent shortage is to use a UPLC system and UPLC columns. If you scale from a 15 cm x 4.6 mm 5 micron column to a 5 cm 2.1 mm 1.7 micron UPLC column, you reduce the solvent consumption per assay roughly 15-fold. You also speed up the analysis nearly 10-fold, which is a win-win situation.

hhmmm, I did use the UPLC and must sayt that I am not really satisfied. The use of 75 µm ID columns packed with 3 µm particles and classic NAN HPLC by LC Packings was much better in terms of identified substances, sequence coverage etc. BTW, you can reduce solvent consumption on that systems (Dionex/LC Packings) by replacing the NAN splitter (1/1000) with the CAP splitter (1/300). It works wonderful with the U3000 systems and the acetonitrile consumption went significantly down. However, the best would be to compose mobile phase without acetonitrile. In our laboratory, successful experiments with ethanol and 1-propanol were made.

We got lucky at our university - our store still had the ACN at before-shortage price level. However it's now not our usual brand (was Caledon distilled in glass grade - now it's mallinckrodt HPLC-grade). So we have now a years supply and I might run into the problem that my prof will ask me to make the HPLC-grade to distilled-in-glass-grade. Does anybody have a SOP or is there a paper so I can check to make sure not to mess it up?

some extra details: our vendor (KSE Scientific) told us that they simply don't know when there is going to be more around - could be January 2009 or 2010.

You're lucky to have the Mallinckrodt material instead of Caledon. We tracked some serious problems in our lab back to inconsistent quality of the Caledon ACN and MeOH that was causing us serious problems with customers. Sometimes you get a good bottle, and sometimes you open a bottle and it is significantly contaminated. This created a lot of non-polar "garbage" with reverse phase methods with gradients sweeping from low to high organic and short wavelength UV detection (you would think the weak solvent would be the most likely culprit - but we were able to prove beyond a shadow of a doubt that our problems were actually being caused by the strong solvent!). We switched to J. T. Baker and we're much more satisfied.

Our vendors are cutting back and cutting back our ACN rations, so at the moment we're responding by accelerating the process of transferring methods to the UPLCs and considering any places where we can feasibly try using MeOH instead of ACN. So far it seems like no end in sight to this thing

Hi,
Another option to save still more solvent during your isocratic chromatographic run is to use the SolventTrak mobile phase recycler system.

SolventTrak Adventages:

1. Cheaper alternatives
2. Quick and easy implementation
3. It can be used in any isocratic HPLC method
4. No change to the actual method
5. Decrease analysis cycle time since less preparation of mobile phase is required
6. It will save still more solvent
Note: After isocratic HPLC method has been developed, (reducing the column size, using UPLC system, or replacing ACN), you can save still more solvent using the SolventTrak mobile phase recycler system.

7. Less HPLC waste will be generated
8. Less disposition costs related to the HPLC waste.

This ACN Shortage situation should be used to be more cost-effecftive and friendly with the environment.

For more information see the following link
http://greenlab.ws/green_lab_5_011.htm

From talking to some of our clients it looks like the situation is getting blown out of proportion. We have many manufacturing contacts in the far east and only one is concerned about the supply of ACN.

The likes of solvent recycler suppliers and Waters are jumping on the back of this to scare people into buying the products.

Working in a large pharma company I know that we are on a guaranteed supply and therefore this is likely to have a knock on effect on smaller companies. We are in a great position as with the size of our contract if supplier A can't fulfil our needs then supplier B will fall over themselves to help us.

Chris,
Good for your large pharma!
Have you got any suggestions to help "smaller companies"?
I have had a back order for acetonitrile cancelled.
Smaller companies was supposed to mean better competition and more efficiency in days of Maggie Thatcher!!!!
WK

I don't agree with how the situation is being handled but have just been told we have nothing to worry about.

I used to work in a small lab so know how hard it can be. It just annoys me that a forum that just ysed to be used for sharing information is now being used as a sales tool.

If I could distribute some of our supply I would, share the wealth and there would be fewer problems. We are also ensuring that some of our contract manufacturers QC labs have enough ACN free of charge.

It sounds like some of the gasoline "shortages", that perhaps some large pharmaceutical users found out early and stockpiled, so that hoarding is hurting others. Maybe similar to the fear factor of people topping off their fuel tanks with a few gallons because of fear of running out.