Question

In the analysis of odorants in tequila in Figure 24-21, tequila was diluted with water and extracted four times with dichloromethane$\left({\mathrm{CH}}_2{\mathrm{Cl}}_2\right)$ , b.p. ${\mathbf{40}}^{\mathbf{\circ }}\mathbf{C}$The$\mathbf{400}\mathbf{}\mathbf{mL}$of$\mathbf{\left(}{\mathbf{CH}}_{\mathbf{2}}{\mathbf{Cl}}_{\mathbf{2}}\mathbf{\right)}$was evaporated down to$\mathbf{1}\mathbf{}\mathbf{mL}$and$\mathbf{1}\mathbf{\mu L}$of the extract was injected on-column onto a poly(ethylene glycol) open tubular column $(30m\times 0.53\mathrm{mm},\mathrm{film}\mathrm{thickness}=1\mathrm{\mu m})$, film thickness ) initially at and then ramped to ${\mathbf{230}}^{\mathbf{\circ }}\mathit{C}$

(a) Why was the diluted tequila extracted four times with dichloromethane instead of once with a larger volume?

(b) Why was on-column injection used?

(c) Why was a poly(ethylene glycol) column chosen for this application?

(d) What was the phase ratio of the column?

(e) Why was a wide-bore 0.53-mm-diameter column chosen for this application?

Short answer

(a). As a result, diluted tequila is extracted four times with dichloromethane rather than once at a higher volume.

(b).On-column injection minimises the likelihood of heat degradation as well as the odour of a larger number of molecules.

(c). The use of poly (ethylene glycol) in the column is due to the fact that poly (ethylene glycol) is a polar column, which is ideal for polar analytes.

(d).The column's phase ratio $\mathrm{\beta }$is 132.

(e).As a result, a wide-bore column with a diameter of$0.53\mathrm{mm}$ enables for bigger injections of compounds, the scent of the components can be recognised during elution.

Step-by-step solution

Definition of dichloromethane

• Methylene chloride, often known as dichloromethane, is a colourless liquid with a slight pleasant odour that evaporates quickly and does not burn easily.
• It's frequently used as a paint stripper and an industrial solvent.

Determine the diluted tequila extracted four times with dichloromethane instead of once with a larger volume

(a)

• It must be explained why diluted tequila is extracted four times with dichloromethane rather than once with a larger volume.
• To explain why diluted tequila is extracted four times with dichloromethane instead of once with a larger volume.
• Small extractions repeated several times have been found to be more significant than a single extraction. As a result, diluted tequila is extracted four times with dichloromethane rather than once at a higher volume.

Determine the on-column injection

(b)

• It is necessary to explain why on-column injection is used.
• On-Column Injection: For thermally sensitive chemicals, on-column injection is the optimum method for quantitative analysis.
• It's a low-resolution approach that won't work for columns smaller than a certain diameter$0.2\mathrm{mm}$.
• On-column injection can be used to handle both large and small amounts of dilute and concentrated solutions.
• To describe how on-column injection is used.
• On-column injection minimises the likelihood of heat degradation as well as the odour of a larger number of molecules.

Determine the poly(ethylene glycol) column chosen for this application 

(c)

• It is necessary to explain why a poly (ethylene glycol) column was used.
• To describe how to use a poly (ethylene glycol) column
• The retention index of the compounds is determined by the total polarity phases as well as the selectivity of each column's polar interaction types.
• The use of poly (ethylene glycol) in the column is due to the fact that poly (ethylene glycol) is a polar column, which is ideal for polar analytes.

Determine the phase ratio of the column

(d)

It is necessary to compute the phase ratio $\beta$

Phase ratio $\mathbf{\beta }$

The dimensionless phase ratio is the volume of the mobile phase divided by the volume of the stationary phase. The phase ratio is determined as follows:

$\mathrm{\beta }=\frac{\mathrm{r}}{2{\mathrm{d}}_{\mathrm{r}}}$

Where,$\mathrm{\beta }$phase ratio

r is the column's radius.

$$\begin{gathered} {\mathrm{d}}_{\mathrm{f}}=\mathrm{temporal}\mathrm{thickness}\mathrm{of}\mathrm{the}\mathrm{stationary}\mathrm{phase} \\ \mathrm{Increase}\mathrm{in}\mathrm{thickness}\mathrm{of}\mathrm{stationary}\mathrm{phase},\mathrm{decreases}\mathrm{in}\mathrm{\beta }\mathrm{that}\mathrm{increases}\mathrm{the} \\ \mathrm{retention}\mathrm{time}\mathrm{and}\mathrm{capacity}\mathrm{of}\mathrm{sample}. \\ \mathrm{To}\mathrm{figure}\mathrm{out}\mathrm{the}\mathrm{phase}\mathrm{ratio}\mathrm{\beta } \\ \mathrm{Given}, \\ \mathrm{Diameter}\mathrm{of}\mathrm{column}=0.53\mathrm{mm} \\ \mathrm{Thickness}=1\mathrm{\mu m} \\ \mathrm{The}\mathrm{column}\text{'}\mathrm{s}\mathrm{phase}\mathrm{ratio}\mathrm{is}\mathrm{computed}\mathrm{as}, \\ \mathrm{\beta }=\frac{\mathrm{r}}{2{\mathrm{d}}_{\mathrm{t}}} \\ \mathrm{\beta }=\frac{0.265\mathrm{mm}}{0.002\mathrm{mm}} \\ \mathrm{\beta }=132 \\ \mathrm{The}\mathrm{column}\text{'}\mathrm{s}\mathrm{phase}\mathrm{ratio}\mathrm{\beta }\mathrm{is}=132. \end{gathered}$$

 Step 6: Determine the wide-bore 0.53-mm-diameter column chosen forthis application

(e)

• The reason for the wide-bore column's$0.53\mathrm{mm}$ diameter must be explained.
• To explain why a wide-bore column with a diameter of$0.53\mathrm{mm}$ was chosen.
• Because a wide-bore column with a diameter of $0.53\mathrm{mm}$enables for bigger injections of compounds, the scent of the components can be recognised during elution.