Peak broadening

Hi Margot,

It may well be that the column performance has deteriorated so much within the 7 months that the EasiVial standards are measured with poorer PDI values. The column performance can be tested with regular plate count determinations. It is a measure of the quality of the entire system and is closely related to the columns. Butylhydroxytoluene or toluene can serve as a standard for THF applications e.g. (2 mg/mL in the running medium). Has the elution volume also shifted from the peak maxima? Have you added a flow marker to the vials or measured a blank regularly - has the elution volume shifted here?
Of course, the standards themselves could also be the problem; however, in the case of polystyrenes for calibration this is rather unusual. 
In addition to standards and columns, clogged filters (if used) before the detectors could also be problematic. However, this would also be reflected in increased system pressure, for example. 

B rgds,

Anne

Hi Margot,

It may well be that the column performance has deteriorated so much within the 7 months that the EasiVial standards are measured with poorer PDI values. The column performance can be tested with regular plate count determinations. It is a measure of the quality of the entire system and is closely related to the columns. Butylhydroxytoluene or toluene can serve as a standard for THF applications e.g. (2 mg/mL in the running medium). Has the elution volume also shifted from the peak maxima? Have you added a flow marker to the vials or measured a blank regularly - has the elution volume shifted here?
Of course, the standards themselves could also be the problem; however, in the case of polystyrenes for calibration this is rather unusual. 
In addition to standards and columns, clogged filters (if used) before the detectors could also be problematic. However, this would also be reflected in increased system pressure, for example. 

B rgds,

Anne