What is chromatography?
Chromatography is defined as "a physical separation method in which the components of a mixture are separated." Chromatography can separate delicate products. This separation involves the mixture to pass from a mobile phase, through a stationary phase, which then results in isolation of the desired molecule or compound. Two different samples can be run through this method. These two samples can then be compared through an analytic process which the criminalist will do. This process is simply putting the data side by side and comparing them by the eyes of the forensic scientist. Some current labs use transparent copies of the separations so the samples can be compared on top of one another. For example, criminalist can match more than one types of inks that have been used by separating the colors then seeing if they match. The results can simply be placed next to one another and compared. (C.30)
Chromatography
The Process
1. The first step is to inject the feed (substance) into the mobile phase (flows through the system by action pump).
2. Separation in the column occurs next. As the sample flows through the column, its different components will adsorb to the stationary phase to varying degrees.
3. Next, elution of the column will occur. The different components of the feed will elute form the column and different times. The least affinity for the stationary phase (the most weakly adsorbed) will elute first. In contrast, those with the greatest affinity for the stationary phase (the most strongly adsorbed) will elute last.
4. The final step is detecting the different components that have emerged from the column. A detector will analyze the differences in each component eluted.
Below is the process of column chromatography.
Sketch of chromatography process. (I.29)
Different inks that have gone through chromatography. (I.30)
Breakdown of chromatography. (V.3)
Column Chromatography
The process of column chromatography. (V.4)