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Help? Does any one know of sources in Australia?
Posted: Tue Mar 10, 2009 12:26 am
by kerrieb
Hi
Does anyone know of sources in Australia for ACN. Crown Scientific our usual supplier have just qouted me 6 months when I rang up to find out how far away my order I put in 6 weeks ago.
I now have 1 L left in the lab. And we have just started up production on one product again that I need it for sample prep.
If not any reliable (consistant quality) sources in China, we import all our raw materials directly from there anyway
Regards
Kerrie
Posted: Tue Mar 10, 2009 1:39 pm
by CPR
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.......
Equivalent percentages of methanol vs. acetonitrile or another solvent don't necessarily mean equivalent eluent strength. In order to achieve this, you would need to consult a nomogram like this (sorry for the small size...it's the only one I could find on short notice).
The top is %ACN, middle is %MeOH and bottom %THF. Selectivity might not be the same, but this will get you closer than simply switching 50% MeOH for 50% ACN or whatever the composition...according to the chart, 50% ACN would be 60% MeOH or so, for example...good luck!
CJ Rassbach
Posted: Tue Mar 10, 2009 6:49 pm
by Uwe Neue
One has to be very careful about these conversion rules. The reason is that the solvent selectivity affects the conversion significantly, and so does the stationary phase.
Here are some published equations (with the authors), unfortunately in a form that is explicite for acetonitrile. The equations describe the relationship between the volume fractions of the different solvents:
Haddad:
MeCN = 0.9*MeOH^2 - 0.21*MeOH + 0.126
Schoenmakers:
MeCN = 0.23*MeOH^2 + 0.57*MeOH
In my research I found that the equation depends also on the type of bonded phase
C18 and C8:
MeCN = 0.25*MeOH^2 + 0.63*MeOH
EPG phases:
MeCN = 0.8*MeOH
Please remember that all these equations are just rules of thumb, which will vary with your analytes, especially if you have ionic analytes.
Posted: Wed Mar 11, 2009 2:54 pm
by JimH
I'm not having much luck eliminating acetonitrile from my prep and analytical methods either. Unfortunately, it works quite well compared to other solvent systems!
Currently we are analyzing and purifying a variety of peptide sequences in 0.1% TFA mobile phase. The best I seem to be able to do is 2:1 MeCN:IPA in the B phase. Any greater, and the backpressure becomes unacceptable. Methanol doesn't seem to be an option in our case, as I am seeing methyl ester formation in peptides and building blocks unless I go with 0.01% TFA or 0.1% formic acid. Now we are hearing the shortage could persist through 2009... fantastic!
Posted: Wed Mar 11, 2009 8:02 pm
by tom jupille
I put the arm on John Dolan to record a "mini-seminar" that summarizes some of the issues. You can view/listen to it here:
http://www.lcresources.com/more_resourc ... p?f=3&t=20
Note that you will have to register (free) in order to access it.
Re: Help? Does any one know of sources in Australia?
Posted: Thu Mar 12, 2009 2:43 am
by jorry
Hello,
We are supplier of HPLC acetonitrile from China.Our spec is below:
ASSAY(BY GC) % MIN 99.9
WATER (BY KF) mg/kg MAX 100
RESIDUE AFTER EVAPORATION mg/kg MAX 2.00
TITRATABLE ACID meq/g MAX 0.0008
TITRATABLE BASE meq/g MAX 0.0006
UV ABSORBANCE (1.00-CM CELL VS WATER)
AT 190 nm MAX 1.00
AT 200 nm MAX 0.05
AT 210 nm MAX 0.03
AT 220 nm MAX 0.01
AT 254 nm MAX 0.005
I don't know why the shortage situation is so bad in the world market.If you interest in our product.Please contact me at
jorry@hnharvest.com
Hi
Does anyone know of sources in Australia for ACN. Crown Scientific our usual supplier have just qouted me 6 months when I rang up to find out how far away my order I put in 6 weeks ago.
I now have 1 L left in the lab. And we have just started up production on one product again that I need it for sample prep.
If not any reliable (consistant quality) sources in China, we import all our raw materials directly from there anyway
Regards
Kerrie
Posted: Thu Mar 12, 2009 9:16 am
by Vlad Orlovsky
As far as I know, after talking to two people who buy ACN from China and Russia, the quality is not the same as required for HPLC grade. They are doing THREE distillation two purify ACN from these two countries to get it to the desired quality......plus the price of the raw ACN is not that great.
I think that situation is getting better, two month ago I had offer of $850 for case of 4x4L and two weeks ago it is already $650, still way above $165/case we used to pay.......but we managed to buy ACN from the lab which was going out of business for only $120/case...got lucky and now have ACN for another 7-9 months!
P.S. Plus none of the pharma companies are going to buy 12 MT from unknown supplier of the grade you offer. It is better to approach either reselers or manufactureres with distillation capabilities to bring your ACN to desired spec.
Posted: Thu Mar 12, 2009 8:11 pm
by Chris
I know of a compnay that paid lots for a 250 litre drum of 99.9% ACN only to find it was 95%, I would stay well clear.
Got to love those conversion charts
Posted: Wed Mar 18, 2009 4:16 am
by kerrieb
Required Re-validation
Posted: Wed Mar 18, 2009 10:21 am
by Sahav
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
Could you give any recommendation to what extent a re-validation is required for a HPLC method, when you change the ID of a column, and consequently flow as well as injection volume?
Posted: Wed Mar 18, 2009 12:09 pm
by Uwe Neue
These conversion charts have to be based on some type of experience. From my equations above, you will always end up with more methanol than acetonitrile, except for the Haddad conversion in very high water content, for which it may not apply anyway. From my equation above, 50% acetonitrile will require between 60 and 65% methanol for equal retention.
Re: Required Re-validation
Posted: Fri Mar 20, 2009 3:19 am
by Bryan Evans
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
Could you give any recommendation to what extent a re-validation is required for a HPLC method, when you change the ID of a column, and consequently flow as well as injection volume?
Hi Sahav -
Sorry, I'm the wrong person to ask (I no longer work in a regulated environment).
But even in the (proposed?) General Chapter <621> Chromatography,
I think the recommended limit was to be +/- 25% for column I.D.
So - I imagine changing from 4.6 to 3mm I.D. would require re-validation.
This is just a guess though.
Re: Required Re-validation
Posted: Fri Mar 20, 2009 7:11 am
by Consumer Products Guy
But even in the (proposed?) General Chapter <621> Chromatography,
I think the recommended limit was to be +/- 25% for column I.D.
So - I imagine changing from 4.6 to 3mm I.D. would require re-validation.
This is just a guess though.
Columns are generally avaiable in inner diameters of 4.6mm, 3.0mm, 2.1mm and 1mm, if I'm remembering correctly. So following the guideline of +/- 25% for column I.D., no other i.d. would be acceptable. So that recommended limit is pretty worthless/useless/ridiculous, didn't anyone who actually performed HPLC have a hand in it?
Interesting, for GC, the i.d. limits are greater, so those actually can cover a column that's commercially available.
Posted: Thu Mar 26, 2009 2:09 pm
by aceto_81
a little acetonitrile available
Posted: Wed Apr 01, 2009 12:36 am
by chemist dude
I am sitting on 6X4 liters of HPLC grade (J.T. Baker), unopened, that I have available at cost (our lab budget was trimmed recently). I am in the St. Louis area. I had over-ordered a couple of years ago for a method that was never adopted. End user must be a qualified lab with a legitimate purpose and preferably a real need. I will not ship, but will consider delivery within about a 100 mile radius.
