Whenever the status “No Intercept” or “infinity concentration” is displayed instead of an analyte concentration changes in the quantification process can be performed.

Measured area ratio values which do not intercept with a quadratic calibration curve, result in “No Intercept” or “infinity concentration”. Generally, this can be considered as >ULOQ. To get a value for these particular analytes, the curve fit type may be switched from quadratic to linear. If several plates are analyzed together, it is recommend to change the calibration curve of the affected analytes to linear for all plates.

Customized quantification

Due to large concentration ranges in samples, metabolite concentrations may be above the upper limit of quantification (ULOQ). If a quadratic regression is used for quantification, values above the ULOQ may cause the quantification status “no intercept”. Consequently an adaption of the quantitation process may be necessary.

1.    Perform the quantification according to the kit user manual. In MetIDQ go to MetVAL > Validation or MetSTAT > Data > Display Data and check for which analytes the status “no intercept” is displayed.

2.    Check for which analytes the status “no intercept” is given. Check if the status “no intercept” is given for only some or the majority of samples. If the majority of samples is affected, set the regression that is used for quantification to linear and exclude upper calibration standard level(s), which do not match the regression line. Do so for all affected analytes. Please find an example below.