Which one of the following set of elements can be detected using sodium fusion extract?

The qualitative analysis of organic compounds often employs the well-known lassaigne’s test, more popularly called the sodium fusion test. In this procedure the organic compound is first fused with metallic sodium. The highly reactive sodium converts any hetero-elements present in the molecule into simple, water-soluble inorganic salts, which are then identified by conventional ionic group tests.

We must recall which hetero-elements are actually converted into such ionic forms:

• $$\text{Nitrogen (N)}$$ is converted to $$\text{NaCN}$$.
• $$\text{Sulfur (S)}$$ is converted to $$\text{Na}_2\text{S}$$.
• $$\text{Halogens (X = Cl, Br, I)}$$ are converted to $$\text{NaX}$$.
• $$\text{Phosphorus (P)}$$, if present, is oxidised to $$\text{Na}_2\text{HPO}_4$$ by adding an oxidising agent (generally $$\text{NaNO}_3$$) during the fusion.

These inorganic ions are then detected by their specific confirmatory tests:

$$\text{CN}^- \; \overset{\text{FeSO}_4/\text{FeCl}_3}{\rightarrow}\; \text{Prussian blue}$$,

$$\text{S}^{2-} \; \overset{\text{Acetate‐buffered Pb}^{2+}}{\rightarrow}\; \text{Black PbS}$$,

$$\text{X}^- \; \overset{\text{AgNO}_3}{\rightarrow}\; \text{AgX precipitate}$$,

$$\text{HPO}_4^{2-} \; \overset{\text{(NH}_4)_2\text{MoO}_4 + \text{HNO}_3}{\rightarrow}\; \text{Canary yellow } (\text{NH}_4)_3\text{PO}_4\cdot12\text{MoO}_3$$.

On the other hand, $$\text{Oxygen}$$ and $$\text{Carbon}$$ are always present in organic compounds and do not need special detection; moreover they do not form such simple ionic derivatives with sodium that can be identified by ordinary wet tests during a sodium fusion.

Hence, the elements that are detected by sodium fusion extract are sulfur, nitrogen, phosphorus and halogens.

Looking at the given choices, Option A lists exactly these four elements.

Hence, the correct answer is Option A.