Reagents for Nitrogen Oxides Analysis

The analysis of oxides of nitrogen (NOx) typically involves methods that first convert NOx into nitrite ions ($NO_2^-$) or involve reactions sensitive to nitrogen oxides. A common approach uses colorimetric detection.

Key Reagents and Their Roles

The question asks for the set of reagents used in the analysis. Let's examine the components of the correct option:

• Sulphanilic acid: This aromatic amine is a primary reagent in the Griess reaction. It diazotizes in the presence of nitrite ions ($NO_2^-$).
• NEDA (N-(1-Naphthyl)ethylenediamine dihydrochloride): This coupling agent reacts with the diazotized sulphanilic acid to form a highly colored azo dye. The intensity of the color is proportional to the concentration of nitrite (and thus NOx).
• H₂O₂ (Hydrogen Peroxide): Often used in specific procedures for NOx analysis, potentially aiding in the conversion or reaction steps.
• HNO₃ (Nitric Acid): Can be used as a standard or involved in the sample preparation or reaction mechanism depending on the specific analytical protocol for NOx.

Evaluating Other Options

Other options are less suitable:

• Option 2 uses Sulphamic acid, which can sometimes substitute for sulphanilic acid, but sulphanilic acid is the classic Griess reagent.
• Option 3 includes Nicotine and H₂O, which are not standard reagents for this analysis.
• Option 4 includes Sulphomolybdic acid and H₂SO₄, which are not the primary reagents for the standard colorimetric NOx analysis using the Griess method.

Conclusion

The set comprising Sulphanilic acid, NEDA, H₂O₂, and HNO₃ represents a combination of reagents commonly employed in specific analytical methods for the determination of oxides of nitrogen.