Capacity megabore columns

For most of the columns listed in Table D 1.2.1, various dimensions are available for each of the column types. Generally, a column with an i.d. from 0.20 to 0.32 mm is regarded as a capillary column. A column with an i.d. of 0.45 or 0.53 mm is called a megabore column. Both capillary and megabore columns are commonly used in FAME analysis. There are advantages and disadvantages for both capillary and megabore columns. Capillary columns have better resolution but less sample capacity,... 

Commercial columns are available with stationary phases that vary in thickness from 0.1 to 5 /rm. Film thickness primarily affects the retentive character and the capacity of a column, as discussed in Section 30E-6. Thick films are used with highly volatile analytes because such films retain solutes for a longer time, thus providing a greater time for separation to take place. Thin films are useful for separating species of low volatility in a reasonable length of time. For most applications with 0.25- or 0.32-mm columns, a film thickness of 0.25 xm is recommended. With megabore columns, 1- to 1.5- JLm films are often used. Today, columns with S-pm films are marketed. 

A 0.53-mm-i.d. column offers the best of both worlds, because it combines the attributes of a fused-silica capillary column with the high sample capacity and ease of use of a packed column. Analytical methods developed with a packed column can be easily transferred for many applications to a megabore column... 

A 0.53-mm-i.d. column offers the best of both worlds, because it combines the attributes of a fused-silica capillary column with the high sample capacity and ease of use of a packed column. For many applications, analytical methods developed with a packed column can easily be transferred to a megabore column with the appropriate stationary phase. Peaks generated with a megabore column typically are sharper and exhibit less tailing compared to those with a packed column. Redistribution of the stationary phase can occur at the inlet of a packed column with large injections of solvent and leave an exposure of silanol sites on a diatomaceous earth support. With a cross-linked phase in a megabore... 

Column inner diameter affects not only resolution but also sample capacity. For example, the megabore column has an excellent capacity at the expense of a sacrifice in resolution offered by the narrower-diameter columns. Analysis times are also shorter, and of course, it remains the choice of choice for direct replacement of a packed column. But it is a column of choice for purity or trace component... 

Capillary columns are available from several manufacturers in a wide range of column internal diameters (O.l-l.Omm), column lengths (5-50 m), and stationary phase film thicknesses (0.1-5.0 pm). Generally, sample capacity increases but the efficiency decreases as the internal diameter or film thickness increases. The larger bore capillary columns with internal diameters between 0.53 and 1.00 mm are termed wide bore or megabore capillary columns and these have similar capacities, but greater efficiencies, than packed columns (see Table 2). 

---