In high pressure liquid chromatography (HPLC), the compound is injected through a column of different sized beads.The amount of time it takes for the compound to pass through the column is the retention time (RT).
In high pressure liquid chromatography (HPLC), the compound is injected through a column of different sized beads.The amount of time it takes for the compound to pass through the column is the retention time (RT). The relative retention time (RRT) is the comparison of the RT of one compound to another.
Relative Response Factor (RRF) is an analytical parameter used in chromatographic procedures to control impurities/degradants in drug substance and drug product. RRF is used to correct the difference in detector response of impurities with analyte peak. RRF is established by the slope method with linear range of solutions.
The relative response factor of impurity = [Slope of Standard solution in curve/ Slope of Impurity solution in curve]
Note: If the impurity slope value is in the denominator, Relative Response factor (RRF) value appears in the numerator (OR) The Relative Response Factor of the drug substance with respect to impurity will appear as multiplication factor in the formula of impurity determination.
Good Q..
IN HPLC, you inject your sample and wait until the compound is detected just after passing the column and this time lag is retention time (RT) just as you said. RT could vary depending on various factors, mobile phase composition, pH, temperature, etc and hence we need an average from several experimental sets. You can reduce this variations if you have a reference compound like an internal standard (IS). You can now reflect the variation of your one or many of your compounds in the sample by using this reference – RT with reference to IS. You can simply report relative RT (RRT) as RT for the IS divided by RT for the compound to be analysed (e.g. A, B, C etc, ) (RRT = RT for IS/RT for A, etc.).
We use relative response factor (RRF) to report the relative abundance of an impurity in comparison to one reference such as active ingredient of a drug. The advantage here is that they are assessed under the same experimental condition and the reporting is simple – we use response facto as a function of peak area divided by concentration ( e.g., mg/ml). The response factor of your impurity divided by the response factor of your active ingredient will give you RRF. One note you should remember is that the response factor depends on which detector you use and even which wave length applied in the UV-based measurement.
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