LOQ of impurities with same RRF

[jayroseville58]

Is it just okay to get a different LOQ values for different impurities at the same RRF?

[HPLCaddict]

Even with the same RRF, different analytes may exhibit different peak shapes and/or peak widths, resulting in different peak heights and thus different signal/noise ratios. Just imagine a simple isocratic separation. The later the retention times, the wider the peaks will be and therefore signal heights (at the same concentration) will decrease with retention time.
So, yes, even with the same RRFs, different analytes may show different LOQs. If this applies to your specific separation, you have to judge for yourself. Remember that LOQs are no absolute values, they may differ considerably depending on the method used for determination and the whole HPLC system (lamp age, column condition, ...).

[jayroseville58]

Even with the same RRF, different analytes may exhibit different peak shapes and/or peak widths, resulting in different peak heights and thus different signal/noise ratios. Just imagine a simple isocratic separation. The later the retention times, the wider the peaks will be and therefore signal heights (at the same concentration) will decrease with retention time.
So, yes, even with the same RRFs, different analytes may show different LOQs. If this applies to your specific separation, you have to judge for yourself. Remember that LOQs are no absolute values, they may differ considerably depending on the method used for determination and the whole HPLC system (lamp age, column condition, ...).

thanks for your very informative response