Chromatography Forum

Hi all!
What are root causes of a highly negative Y-intercept?
How to explain a highly negative intercept based on a linear regression of standards solutions through a range of 20-50ug/ml API? What can cause that?
Conditions: AcNH4 20mM pH 9.2/ACN 70:30 isocratic
Samples: Decapeptide in triethylaminphosphat solution pH 2.3
Column: Phenomenex Kinetex UPLC column

Here are basic informations, ask for more if nedeed.

Thx all

How about the high concentration standards being OK, while at the low end the standards are too low, etc.

Poor sensitivity or/and poor recovery (some of the stuff loaded stays in the column – is it new?), inadequate integration method, injection inaccuracy……………..
For more concrete suggestions, more data are needed - e.g. number of standard curve levels, number of determinations at each level (and variation). And representative chromatogram/s is/are always of great help.

Best Regards

The calibration range (20 - 50 ug/ml) seems very narrow to me - is this usual practise in peptide HPLC ?

It makes the intercept very vulnerable to small variations in the upper and lower points.

Peter