Chromatography Forum

Hello all. I am new to PhEur (or EP) testing. I have plenty of experience with USP testing, but our company is wanting to get into the European market, so I need some help with an EP test.

I am running the Ethanol and Formamide GC assay for Ivermectin. I'm trying to follow the method in the monograph, but I'm getting the IPA and EtOH peaks co-eluting. I've tried lower the initial temp, but I'm only allowed 10%. I'd try lowering the flow, but that will just spread everything out (right?). I don't have access to any other columns, unless I convince my boss to buy another one.

I also don't quite understand why I have to make two different levels of standard (reference, in EP lingo). Do I need to calculate using both, with a linear regression and all that?

Anybody have any experience with any of this?

BTW, I am running on an Agilent 6890, with a J&W DB-WAX 30mx0.53mmx1um column.

Thanks in advance,
Greg

Hi Greg

Seems like you might have made a "small" mistake.

Ethanol and IPA (2-propanol) will coelute under those conditions. However the monograph points to propanol R= 1-propanol.

1-propanol should be separated from ethanol under the given parameters in the monograph.

Yeah, I figured that out... What a dumb mistake. Oh well, live and learn. Using the 1-propanol, the chromatography looks great.

As I was playing with the GC conditions last night, I thought "Man, if only they would have used a different alcohol; like butanol, or a different propanol... Oh crap..."

Thanks... Greg.

Hi Greg,

Wondering if you can provide some advice. We are running the Ph Eur method for formamide and EtOH but are having some issues, we believe with our extraction.

We get nice standard chromatography with all peaks present however when we analyse a sample we are not seeing any formamide. We are expecting to see around 2.4% formamide. We are seeing the correct amount of EtOH (~3.9%). We have done a few simple recovery experiments and when spiking with formamide we are getting 100%.

Are there any tricks we should be looking out for when preparing the sample solutions? We are following the PhEur method to the letter.