Sulphur determination in crude oil: Which method is classically regarded as the best laboratory approach for determining total sulphur in crude oil?

Introduction:
Total sulphur in crude oil is a critical quality parameter affecting corrosion, emissions, and downstream processing. Several classical lab techniques exist, but only specific ones target sulphur directly.

Given Data / Assumptions:

• We compare general organic analysis methods vs energy calorimetry vs sulphur-specific combustion methods.

Concept / Approach:
Kjeldahl and Dumas are primarily for nitrogen determination (Kjeldahl for NH3 from organic N; Dumas for N by combustion). A bomb method can burn the sample in oxygen; combustion gases (SO2/SO3) are absorbed and analysed to quantify sulphur. While modern refineries use e.g., XRF or UV fluorescence, the classical best answer among the listed options is the bomb method associated with bomb calorimeter apparatus and post-combustion sulphur analysis.

Step-by-Step Solution:

Verification / Alternative check:
Classical analytical chemistry texts describe sulphur determination by oxygen-bomb combustion with subsequent titration or instrumental detection of absorbed sulphur oxides.

Why Other Options Are Wrong:

• Kjeldahl/Dumas: Nitrogen, not sulphur.
• Junkar's calorimeter: Measures calorific value of gas; not a sulphur test.
• Hydrometer: Density only; cannot give total sulphur.

Common Pitfalls:
Assuming any calorimeter implies sulphur analysis; only dedicated bomb combustion with absorption and analysis yields sulphur content.

Final Answer:
Bomb calorimeter (bomb method with absorption of combustion gases)