How do I choose the optimal column internal diameter (ID) for my reverse-phase application? - WKB259344

ENVIRONMENT

• Column characteristics

ANSWER

Match the column ID based on the measured system dispersion volume.

(see Additional Information)

 

ADDITIONAL INFORMATION

The bandspread (dispersion) inherent within all LC systems is directly related to the volume in the system's flow path between an injector and a detector (no column installed), which contributes to a loss in efficiency or chromatographic performance/resolution.

 

To achieve maximum efficiency, column IDs should be selected based on your instrument’s specific bandspread value (system dispersion) because columns that have larger volumes (larger column IDs) are less susceptible to negative impact of the system volume (dispersion).

 

Here are some general guidelines on how to determine which column ID is most appropriate for you, based on your system bandspread (dispersion) measurement values:

 

If your system bandspread (dispersion) value is greater than 120 µL:

• You may need to reduce your system bandspread (dispersion) by using tubing with a smaller ID, such as 0.010" or 0.009", in order to run a 4.6-mm ID column successfully.
• You can also try to increase retention time (tR) of the analyte(s) of interest. 
• Peaks that retain longer will elute in more volume and are less susceptible to system bandspread (dispersion) effects.
• A capacity factor of >2.0 is preferred.
• See What is the role and importance of determining the capacity factor of a peak in chromatography?

If your system bandspread value is 80-120 µL, you should be able to run a  4.6-mm ID column without worrying about system bandspread (dispersion) effects.

• You can also try to increase retention time (tR) of the analyte(s) of interest. 
• A capacity factor of >2.0 is preferred.
• Peaks that retain longer will elute in more volume and are less susceptible to system bandspread (dispersion) effects.
• See What is the role and importance of determining the capacity factor of a peak in chromatography?

If your system bandspread value is 26-80 µL, you should be able to run a 3.0-mm ID (or 4.6-mm ID) column without worrying about peak broadening due to your system volume.

• The smaller 3.0-mm ID will help save solvent.
• A 4.6-mm ID would still be a great option, because the wider ID will still be less susceptible to system bandspread (dispersion) effects.

If your system bandspread value is 25 µL or less, you should be able to run a  2.1-mm ID (or 3.0-mm or 4.6-mm I.D) column without worrying about peak broadening due to your system’s bandspread (dispersion) volume.

• A tubing ID of 0.005" is usually used to obtain <25 µL system bandspread (dispersion) volumes.
• 2.1-mm ID columns are preferred to mass spectrometry because of the lower flow rates used in MS methods.
• 25 µL is the highest bandspread value in which a 2.1-mm ID column should be used in terms of how bandspread will negatively affect peak width.
• You can also try to increase retention time (tR) of the analyte(s) of interest. 
• A capacity factor of >2.0 is preferred.
• Peaks that retain longer will elute in more volume and are less susceptible to system bandspread (dispersion) effects.
• If optical detection is being used, a 3.0-mm ID column is recommended if it is packed in particle sizes of less than 2.0 μm.
• Larger column IDs are not as susceptible to system bandspread effects.
• See What is the role and importance of determining the capacity factor of a peak in chromatography?