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Redi-Reckoner 		 
Trace Impurity Analysis
Using LC-MS

RESOLUTION/Loading


Follow this paradigm from a Cogent "Half" Column that has the best selectivity and you will be able to prepare or detect trace impurities. Using a "half" column is low cost and very fast.

Printable Version     What is a Redi-Reckoner?

Click on Chromatograms to View Actual Method Conditions.
Point to Chromatograms for a Brief Description

Increase Column ID and Flow Rate
Mini-Scout
Column
With base line resolved chromatograms from one of the Cogent Kit columns, you can predict results with changes in your column ID. From 4.6mm to 7.8mm as shown below, you can predict the increased resolution.
75mm x 4.6mm
1ml/min
This Chromatogram shows the increased resolution with the same sample loading and method conditions. The time of analysis is slower due to equal flow rates. The back pressure is only 20% of previous Chromatogram.
75mm x 7.8mm
1ml/min
This chromatogram shows a ten fold increase in sample loading and a five fold increase in flow rate. Back pressure is acceptable but here we show a 200% increase in sample load. Analysis times is acceptable and base line resolution is maintained.
75mm x 21.2mm
1ml/min



Increase Column Length

This chromatogram shows a large gain in resolution with the same sample load and method conditions as above. The length was increased while the ID was maintained. Back pressure was acceptable and this indicates that with a longer column you could load more sample.
100mm x 21.2mm
1ml/min
This chromatogram shows an increase in column length and the other method conditions are maintained. Back pressure is acceptable but the sample loading is almost two orders of magnitude greater without the loss of resolution.
250mm x 21.2mm
5ml/min
 
  This chromatogram shows a doubling of the flow rate the improve speed of analysis and the sample load was further increased by a factor of five. The marker peak Uracil was deleted from this chromatogram for convenience.
250mm x 21.2mm
15mg load
10ml/min

  The chromatogram shows a maximum sample loading and speed while maintaining base line resolution. Here the sample load is further increased by 200 times , back pressure is still acceptable but at the upper limit of acceptance. Resolution is low but base line resolved. The Kit column had a sample load of 0.00125mg and the final chromatogram shows a sample loading of 100mg, a difference of almost 4,500%. The marker peak Uracil was deleted from this chromatogram for convenience.
250mm x 21.2mm
300mg load
10ml/min

This last chromatogram shows that trace analysis can easily be accomplished with this Redi-Reckoner™. Sample loading can be increased while acceptable resolution is maintained allowing for increased detector recognition.


Use this Redi-Reckoner™ to predict optimal HPLC column sizes and increased flow rates for maximum detection of Trace Impurity amounts in the shortest time possible.

It is very well known that resolution can be increased by increasing column length but at the cost of increasing back pressure and limiting your ability to increase flow and decrease time. This can be a problem when you want to load more sample on your column for trace amount analysis.

In this RR we show that you can get the same or better resolution by keeping the column length constant and increasing column ID. You can increase the flow rate keeping time of analysis acceptable due to less back pressures limits as shown in the first three chromatograms.


 

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