Chromatography Forum

Hi,

We need to control the absence of dimethyl sulphate in a raw pharmaceutical intermediate product inside a synthetic route.

Does anyone have any method or suggestion how to do it?

We have been working with a GC with HP-1 30 mts x 0.25 mm DI and 1 µm film thickness, with a FID detector but I have a lack of sensitivity (only 100 ppm).. Product is disolved in CH2Cl2 and injected 5 µl in split mode.

We are working to improve its sensibility but we are far from our limit requiere

Thanks

Basil

You need a more selective and sensitive detector
You should try wiht an FPD,if you have one or ecd.
With an FID it's hard to monitor trace of sulfur compound,harder in split mode.

Dear Basil,

I would recommend using a PFPD or FPD detector. These detectors are more selective towards sulfur compounds. Another appreach is using an AED detector. It is even more selective.

Regards,
Ingo Christ

Unfortunately we do not have detector FPD, reason why we will have to make the service of analysis in an alternative laboratory to ours.

Some other suggestion to make agile the development will be appreciate due to we have one week to resolve the problem.

Thanks again

Hi Basil,

How about increasing the sample size and use some type of extraction technique such as SPME, SDME or SPDE. The cheapest one is SDME (Single Drop Microextraction). You only need a drop of a high boiling liquid, which is able to dissolve your compound of interest and then dispense it into the headspace your sample. After some time, pull the drop back into the syringe and inject in into your GC. You can read more about this technique on:
http://www.chromsys.com/Applications/sdme.htm

There was an article in the LCGC Europe this past November on that topic as well.
Regards,
Ingo

You say split,but what are your split ratio?

Why don't you try splitless.

Coul you dissolve your drug in hexan?
We have a method like you with FID ,drug in hexan,toluene as ISTD,it works good,but should work with CH2CL2

column db1 30*0.53*5um
He 50Kpa
oven 60°C 1 min-5°C/min to 150°C
Injection 140°C Volume :2uL

We will try splitless in order to increase sensitivity.

xxxx... could you send me a document with complete method ?.

Which is the final sensitivity of the method ??

We will try with hexan..

Thanks in advance again

Basil

BasilAttckinson@hotmail.com