Because this type of columns are generally used in standard in oficial methods. Methods that were develop several years ago where done with this type of columns. And nobody has taken the time and effort to update them (specially if they work). THere is no problem if you develop and validate your methods with smaller columns ( the smart way) since you will save time, solvents and money. Wich is great if you are working in a cash starved university and you will get home early
Dear Bhupendra Shrestha,
Your question is much pertinent.
I would try to explain to you saying people have been very involved with the intricate 250x4.6mm columns culture, as the old 254nm detection culture. Look to any pharmacopeia (it can be the Indian, Pakistani, European, US, British, Korean, Japanese, Chinese, Brazilian, and etc) and it will be there, so strong, transmitting us a false ideia that this column length is the better, which can be true but for some cases since the marketing offer us several possibilities for improve good and/or better chromatographic separations using shorter columns.
So, if you are involved with method development, please, dare with shorter columns and you may get fantastic and happy surprises.
Have nice elutions!
Carlos de Souza Teixeira
http://br.linkedin.com/pub/carlos-de-souza-teixeira/15/7b0/125
Every column dimension has its own application. Sometime we spare some more time to get best rather than better. So same is in the case of column dimension chemistry.
Because this type of columns are generally used in standard in oficial methods. Methods that were develop several years ago where done with this type of columns. And nobody has taken the time and effort to update them (specially if they work). THere is no problem if you develop and validate your methods with smaller columns ( the smart way) since you will save time, solvents and money. Wich is great if you are working in a cash starved university and you will get home early
Nice suggestions carlos...i think hearing from people like you boost my confidence more...thnx
It's probably an old method that noone bothered to modernize and validate.
Hi Dear,
Just adding to above that Our first target is to separate better for this we want to see well resolved peaks,bigger column diamention give us chance to load more as capacity factor/if loaded less base to base separation or more resolved chrmatogram.Developing method on smaller is sometime difficult as small particle size in small column gives back pressure problems...but if the matrix is simpler in terms of no of component then it can be well tried directly on small column.
It seems the column is an analytical one where you can load at max 100microl. Increasing the column length gives better resolution because the number of threotical plates increases.
I think use of longer columns will definitely improves theoretical plates
4.6 mm X 250 mm columns are typically meant for semi-preparative purposes, while 2.1 mm X 150 mm or in some cases 2.1 mm X 100 mm columns are mostly meant for analytical chromatography applications. Depending on the amount (i.e. concentration and volume) of sample that is to be injected, the choice of the column needs to be decided. It is correct that longer columns would provide better separation (i.e. better resolution) than shorter columns due to higher number of theoretical plates in the longer columns than that of the shorter. Nevertheless, shorter columns are more useful/suitable for LC-MS experiments. For LC-MS runs, involving electrospray ionization (ESI) - mass spectrometry (MS), 2.1 mm X 100 mm or 2.1 mm X 50 mm can be more suitable. For such small columns, lower flow rates are recommended, say of the order of 100 microlt./min or 50 microlt./min. These flow rates are very much apt for ESI. Also, the amount (i.e. concentration and volume) of sample to be injected for LC-ESI-MS experiments need (must) not be very high. Hence, smaller columns are suitable for LC-ESI-MS experiments.
- Badges
- Science method