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- Posts: 62
- Joined: Wed Mar 02, 2005 9:39 am
I store the columns in AR THF. This is recommended by the manufacturer of the columns.
I have two columns sets, one for low and one for higher molecular weights. I recalibrate when I changed from columnset or I filled up the recipient of THF.
I use toluene as retention time reference. The window of this reference peak in the calibration file is set to 1%. If the reference peak in the samples are outside this window, I start to investigate the reason. It could be a small leak (when the retention time has increased) or something else like a reduced efficiency of voids in the columns. I protect the analytical columns with a guard column. In any case, when something has changed to the system, I run calibration standards.
Preparation of the standards: I use 3 callibration solutions, having 9 standards. I estimate the linear range of the columns and divide the standards equally over this range (using the log Mp of the standards.). The concentration is 0.03% w/v for each separate standard. So solution 1 has the highest MW of the range, solution 2 the second highest, solution 3 the third highest, solution 1 the fourth highest and so on.
I tend to keep the concentration as low as possible. On the website of WATERS there is a very good GPC primer (http://www.waters.com/waters/nav.htm?cid=10167568). In this primer you will find a recommendation for the concentration of the sample, which depends on the molecular weight.
It is always a good idea to filter your sample through a membrane filter. In general I use a 0.45 µm PTFE filter. Be gentle when you push your sample through the filter. You do not want the shear it and (possibly) beak up any polymer chains. This goes for very high molecular weight materials.
I have two columns sets, one for low and one for higher molecular weights. I recalibrate when I changed from columnset or I filled up the recipient of THF.
I use toluene as retention time reference. The window of this reference peak in the calibration file is set to 1%. If the reference peak in the samples are outside this window, I start to investigate the reason. It could be a small leak (when the retention time has increased) or something else like a reduced efficiency of voids in the columns. I protect the analytical columns with a guard column. In any case, when something has changed to the system, I run calibration standards.
Preparation of the standards: I use 3 callibration solutions, having 9 standards. I estimate the linear range of the columns and divide the standards equally over this range (using the log Mp of the standards.). The concentration is 0.03% w/v for each separate standard. So solution 1 has the highest MW of the range, solution 2 the second highest, solution 3 the third highest, solution 1 the fourth highest and so on.
I tend to keep the concentration as low as possible. On the website of WATERS there is a very good GPC primer (http://www.waters.com/waters/nav.htm?cid=10167568). In this primer you will find a recommendation for the concentration of the sample, which depends on the molecular weight.
It is always a good idea to filter your sample through a membrane filter. In general I use a 0.45 µm PTFE filter. Be gentle when you push your sample through the filter. You do not want the shear it and (possibly) beak up any polymer chains. This goes for very high molecular weight materials.
Regards,
Gilbert Staepels
Ideas mentioned in this note represent my own and not necesseraly those of the company I work for.
Gilbert Staepels
Ideas mentioned in this note represent my own and not necesseraly those of the company I work for.
