Chromatography Forum

Hi, There is a useful website about Saving Acetonitrile at

http://www.sigmaaldrich.com/europe/acet ... vings.html

There is a useful calculator and a good article about switching to Methanol.

I don't think the calculator at the site mentioned in the last post is terribly smart. When you switch from a 25 cm 3 micron column to a 15 cm 2.7 micron column, you loose nearly half your plates. This should not be the purpose of a proper scaling exercise.

I tried to get my boss to let me hord, but he said no and now we are suffering from the consequences.

Seriously, though. I think we'll be ok. I'm looking into getting the SolventTrak and substituting methanol for acetonitrile. Phenomenex is helping me transfer my methods using their smaller bore columns also.

Paladin,

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

It is almost as simple as the area math discussed by several previously.
However, if using gradient methods, you have to consider the (pump) dwell volume. It may differ 1 mL between pump models.
Using 2 mm column with 0.5 mL/ min instead of 4.6 mm columns with 2 mL/min, the peak retention time may increase considerably, when using fast gradients.

Either 1) Accept the retention time change, 2) Modify the pump (if possible) 3) Buy a pump with lower dwell volume 4) Buy a complete expensive new LC with low dwell volume, for instance a hyped UPLC. The injectors and detectors usually cause less problems.

Hello,

Being a new forum-visitor, im not sure whether it is the best to write in, but this is one of the most updated one.
I have a HyperClone C18 ODS (150*3,2*3) column, and it has worked so far very well. Some days ago it looked to have contaminants; i made a blackflow with the following protocol: ACN-water 5/95, then THF, and after ACN/water 95/5. After this it looked to be ok and work. I made 2 run (ACN / water + AA; from ~20%-100%; i had been using this column such system before). Now i changed ACN to methanol (20% metanol), and the pressure flied into the sky. I tried to wash with 100% ACN, then 100% methanol and blackflow, too, it was all right, but next time with the system mentioned previously pressure has gone up again.
This is the problem. Any advice...?

Methanol-containing mobile phases will nornally run at higher pressures (due to higher viscosities of methanol-aqueous mixtures). Try raising the column temperature to 40C, slowing flow rate, etc.

All I have to say is that its been an absolute minefield trying to resolve the problems associated with the shortage because theres' no shortage of sales people heavily plugging their products as a solution without really thinking about the intended applications of their clients.. Waters being the most obvious with the Acquity surge.

With sufficient method development or re-development I think switching to MeOH, THF, or IPA is viable (depending on application) for analytical work.

But I'm doing preparative HPLC work right now and it is a heck lot harder to switch over to methanol as I haven't been able to find any sensible way to heat the mobile phases up to reduce backpressure at the flow rates that the separation needs to run at.

But I'm doing preparative HPLC work right now and it is a heck lot harder to switch over to methanol as I haven't been able to find any sensible way to heat the mobile phases up to reduce backpressure at the flow rates that the separation needs to run at.

My "modified" Agilent 1100 prep system uses either a 70 litre ( for 50mm diameter ) or 40 litre ( for up to 30mm diameter columns ) cheap plastic garage bins ( or unused lab sharps bins ) as the column heater water tank with a 1/2" pump thermocirculator providing the temperature control. It can control to 80C OK.

The advantages are that the guard is placed below the column, both are vertical, it's very cheap, and the 1/16" stainless solvent line heats the mobile phase as it goes to the guard inlet at the bottom.

The disadvantges are that you need to add corrosion inhibitor if you use Al holders, such as Axia, and it takes a while to change column temperature, and it's not portable.

If you want you can also put manual sample valve loops in the water bath. Was thinking of of making it a tropical fish tank as well...

Please keep having fun,

Bruce Hamilton

I just wanted to add my 2 cents to using solvents other than ACN. We have some OTC pharmaceutical products where our ACN-containing mobile phase had the API elute between fragrance ingredient #1 and fragrance ingredient #2.

When we removed ACN and substituted a similar percentage of methanol, API eluted AFTER fragrance ingredient #2 and before fragrance ingredient #3. Yes, the pressure was considerably higher as well, and we did raise column temperature a small amount.

When we next removed methanol and substituted a different solvent, API eluted AFTER fragrance ingredient #3 major component and before fragrance ingredient #3 minor component. We will begin re-validating soon using one of those options. Sample preparations do not use ACN and will remain exactly the same.

For a non-regulated product we're trying to convince our QA department that we should only need to demonstrate equivalency of the chromatography, since the sample preparation will be the same, but they still want a zillion sample preparations done, natch, not just showing the chromatography delivers equivalent results.....love that QA.......

My "modified" Agilent 1100 prep system uses either a 70 litre ( for 50mm diameter ) or 40 litre ( for up to 30mm diameter columns ) cheap plastic garage bins ( or unused lab sharps bins ) as the column heater water tank with a 1/2" pump thermocirculator providing the temperature control. It can control to 80C OK.

That's something that we have in mind but as you say, its not really portable or convenient in any way (ie. corrosion, changing temp will take a long time).

One other suggested option was to put the entire system into a heater compartment

I don't think the calculator at the site mentioned in the last post is terribly smart. When you switch from a 25 cm 3 micron column to a 15 cm 2.7 micron column, you loose nearly half your plates. This should not be the purpose of a proper scaling exercise.

I'm not entirely certain, but I think as the Fused Core columns (ascent express / halo) offer higher efficiencies then switching to a shorter column should see no loss of plate count. There is another document on the Supelco website which which compares a 250mm 5um column with a 100mm Fused Core column and the N for Diaepam is roughly the same.

Our lab has just bought a recycling system to help us - well at least buy us a bit of time!

Has anyone had any luck using ACS grade? What are the significant drawbacks? Consistency? UV cutoff? We are a high volume lab with many different methods utilizing acetonitrile so recycling would not be hugely effective for us. However, we realize we may need to go that route to help as much as possible until this is rectified. Thanks!

CJ Rassbach

Dear all:
There is a blog about the MeCN shortage ("The Great Acetonitrile Shortage. In the Pipeline"), at:
http://pipeline.corante.com/archives/20 ... ortage.php

We had to cut back on our testing, and we were hoping to stretch our inventory into mid-2009. Today, there is hope at the end of the tunnel!

In the comment section at the end of the blog page, you can find contacts of some suppliers from China. It seemed that there is a relief, since we were able to place two orders to 2 suppliers recently. However, the prices are much higher than last year.

i have been reading replies on the forum regarding the shortage in supply of Acetonitrile
am currently studying the industry and would really appreciate if i could get inputs on the expected supply situation of the HPLC grade ACN over the coming months (3 months to 1 year).
thanks a ton.

...elute between fragrance ingredient #1 and fragrance ingredient #2. ...When we removed ACN and substituted a similar percentage of methanol, API eluted AFTER fragrance ingredient #2 and before fragrance ingredient #3...

I couldn't get my old boss to understand how this was possible, even though it is a "text book" case. You have my sympathies...