Question

What is the order of elution of the following compounds from a normal-phase packed HPLC column?

(a) ethyl acetate, acetic acid, dimethylamine

(b) propylene, hexane, benzene, dichlorobenzene

Short answer

High-performance liquid chromatography is an analytical technique which is used to seperate, identify and quantify each components of the given mixture.

Step-by-step solution

Step 1

The order of each compound depens on the polarity of the compounds. The compounds with more polarity will be placed at the last stage and vice versa. The acetic acid is most polar compound in the group and hence placed at the last stage in the group. The plarity of dimethyl amine is lesser than the acetic acid and more than the ethyl acetate in the group. Therefore, the dimethyl amine will placed at the second last stage in the group. The ethyl acetate is placed at the first stage in the group due to the lesser polarity. Hence, order is ethyl acetate, dimethyl amine and acetic acid.

Thus, the order of the compunds is ethyl acetate, dimethyl amine and acetic acid.

Step 2

Similarly, we can estimate the order of elution by disolving them in hexane solution. Due to the effect of solubity in hexane, we get the following order of compounds.

Propylene has greater solubilty than benzene and all others. So, propylene is placed at the first stage of the group and hexane has the least solubility factor and therefore placed last.

Thus, the order of the compounds are propylene, benzene, dichlorobenzene, hexane.