The Hybrid Multisampler enables both flow-through and Feed Injection. These options provide more parameters and flexibility for further resolution optimization.
During classical flow-through injection, the sample is transported to the column as a solvent plug. Therefore, early eluted compounds, which are partially carried by the sample solvent, may breakthrough the column. This behavior can result in bad peak shapes due to so-called solvent effects.
The solvent effect depends on the property of the solvent used for the dilution of the sample. Usually, stronger organic solvents will increase the solvent effects in reversed-phase chromatography applications. Using flow-through injection, the easiest way to reduce the solvent effect is to minimize the sample injection volume.
During Feed Injection, the sample is gradually pushed directly into the mobile phase, giving more flexibility to influence the sample while it is transported to the column. In Feed Injection, the sample is mixed and diluted with the mobile phase. As a result, the sample reaches the column properly mixed with mobile phase and the sample solvent no longer has a significant influence on the separation process and the peak shape.
The dilution degree can be adjusted by varying the injection feed speed. Using a high feed speed reduces the dilution degree of the sample. This reduced dilution degree means that solvent effects may still occur, similarly as for classical flow-through injection. Also, these conditions can only be used for samples, which are diluted in weak solvents. Using a slower feed speed increases dilution degree of the sample. A higher dilution degree results in a reduction of the sample solvent effects and improves the peak shapes of early eluting sample components.
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