1) If a capillary column is left in the GC-FID instrument for 2 months with the instrument switched off, it can potentially affect the performance of the column. Over time, contaminants can accumulate on the column, leading to increased baseline noise, reduced sensitivity, and decreased column efficiency. It is generally recommended to remove the capillary column from the instrument if it is not going to be used for an extended period of time. Storing the column properly, such as in a suitable column storage solution, can help maintain its performance.
2) When choosing between a capillary column and a packed column for analyzing a compound, the preferred column depends on several factors, including the nature of the compound and the analytical requirements. Capillary columns offer higher resolving power, better separation efficiency, and wider temperature range compared to packed columns. They are suitable for separating complex mixtures and analyzing a wide range of compounds. Packed columns, on the other hand, can handle higher sample loads and are better suited for analyzing compounds with high boiling points or those that are thermally labile. In general, capillary columns are the preferred choice in modern gas chromatography due to their superior performance and versatility.