Brand Columns Resolution For Free

Resolution is an important HPLC performance indicator usually assessed by how quickly and how completely target components in a sample separate as they pass through a column. Resolution is measured by dividing the difference in peak retention times by the average peak width.

Column internal diameter (dc) affects efficiency, retention, carrier flow rate, capacity, and pressure drop across the column. It is inversely proportional to column efficiency? halve the column diameter, and double efficiency, increasing resolution by a factor of 1.4.

The advantage of switching to longer columns is that the theoretical plates will increase and so will the resolution. The number of theoretical plates (N) is directly proportional to the length of the column and inversely proportional to the particle diameter2.

K) The resolution (Rs) of a column for two analytes (A eluting before B) is given by Rs = [tR(B) - tR(A)]/[(WA + WB)/2], where W is the baseline width of a chromatographic peak in the same units as the analyte retention time.

Increasing column length As highlighted by Agilent, resolution is approximately equal to a quarter of the square root of length over diameter. In other words, column length is proportional to resolution, column efficiency and therefore separation ability.

So efficiency is a function of, what I say, the column dimensions. Long Column ? To get more efficiency, which will lead to more resolution, you could use a longer column. Double the column length and you'll double your efficiency. Resolution goes up by the square root of two.

A longer column generally improves the separation. The trade-off is that the retention time increases proportionally to the column length and a significant peak broadening will be observed as well because of increased longitudinal diffusion inside the column.

The precolumn's function is to condition the mobile phase before it reaches the sample and main HPLC column. It is used in situations in which the mobile phase is believed to degrade or dissolve the packing material in the main column.

C18 is considered better for separating compounds such as long-chain fatty acids as compared to relatively small organic compounds. It is relatively cheap as it is produced in large amounts by most manufacturers.

The main difference between C8 and C18 column in HPLC is that the C8 column contains octyl carbon chain (C8)-bonded silica as the stationary phase, but the C18 column contains octadecyl carbon chain (C18)-bonded silica.