What difficulty may result if a chromatographic column is not placed in a vertical position?
If a chromatographic column is not placed in a vertical position, it can result in several difficulties in the chromatographic separation process. One of the main difficulties is in the proper flow of the mobile phase. Here's how it works:
1. Gravity-driven flow: In liquid chromatography, the mobile phase, which carries the sample, flows down through the column due to the force of gravity. Placing the column in a vertical position ensures that the gravity-driven flow goes smoothly. If the column is not vertical, the flow may be uneven, causing complications and issues with the separation process.
2. Uneven packing: In chromatography, the stationary phase (typically a solid material) is packed into the column. Placing the column in a vertical position helps in achieving an even and uniform packing of the stationary phase. If the column is not vertical, the packing can become uneven, leading to irregular flow patterns and inefficient separation.
3. Channeling and band broadening: If the column is not in a vertical position, there is a higher chance of channeling, which occurs when the mobile phase follows preferential pathways through the column, bypassing parts of the stationary phase. This can result in poor separation and reduced peak resolution. Additionally, the sample bands may broaden during chromatographic analysis, leading to decreased sensitivity and reduced separation efficiency.
To avoid these difficulties, it is crucial to ensure that the chromatographic column is placed in a vertical position. This allows for proper gravity-driven flow, even packing of the stationary phase, and avoids issues like channeling and band broadening.