Posted by anne on Friday, October 14, 2011 at 6:30pm.
Hi, I have a question on HPLC (high performance liquid chromatography).
The procedure says to use a
4.6 x 150mm x 3um column.
The relative retention time of Impurity B with reference to the main peak is about 0.5min.
If I use a 4.6 x 100mm x 2.7um column, will the relative retention time of Impurity B with reference to the main peak still be about 0.5min?
If I remember, flow rate is proportional to Radius4 /length
So here, your radius has been decreased by (2.7/3)=.9 or .9^4
Length has been shortend by (100/150+.666
so time is inversley proportional to the reciprocal of flow rate, or new time is .5min(.666/.9^4)=.5*1.01609 min
check this.
http://en.wikipedia.org/wiki/Hagen-Poiseuille_equation#Poiseuille.27s_equation_for_compressible_fluids
To determine whether the relative retention time of Impurity B with reference to the main peak will still be about 0.5 minutes when using a different column, we need to consider the key parameters involved in HPLC.
The relative retention time (RRT) is a measure of the separation between two peaks in a chromatogram. It is calculated as the ratio of the retention time of the analyte to the retention time of a reference compound.
In this case, the RRT of Impurity B with reference to the main peak is about 0.5 minutes. To determine if this value will change with a different column, we need to examine the factors that can influence retention time.
One key factor is the column dimensions. The dimensions given for the first column are 4.6 x 150mm x 3um. The first number represents the internal diameter of the column (4.6 mm), the second number represents the length of the column (150 mm), and the third number represents the particle size of the packing material (3 um).
The second column has different dimensions, 4.6 x 100mm x 2.7um. While the internal diameter and particle size remain the same (4.6 mm, 2.7 um), the length of the column is shorter (100 mm).
Changing the column length can affect the retention time. As the length of the column decreases, the separation between analytes can be reduced, resulting in shorter retention times. However, the effect of column length on retention time depends on various factors, such as the type of analytes and the mobile phase used.
In this case, since the column length is shorter in the second column (100 mm compared to 150 mm), it is possible that the retention time of Impurity B with reference to the main peak could be different. It is difficult to determine the exact change without additional information about the analytes, mobile phase, and chromatographic conditions.
To verify the impact of the column change on the retention time, it is advisable to perform a test using the new column and compare the chromatograms obtained. This will provide a more accurate understanding of the specific effects on retention time.
In summary, changing the column dimensions can potentially affect the retention time in HPLC. To determine the impact on the relative retention time of Impurity B with reference to the main peak, it is recommended to perform a test using the new column and compare the results to the original conditions.