Emulsion Test for Lipids Relies on Ethanol Dissolution and Water Emulsification

Steps:

• Recall standard procedure: Add ethanol to sample to dissolve lipids, then add water and shake for cloudy emulsion.
• Compare choices to this sequence, noting sample is typically in initial tube with water or directly.
• Eliminate options with wrong order, extra steps, or missing cloudiness indicator.
• Select D as it matches adding ethanol to water-based sample tube, followed by shaking for cloudiness.

Why D is correct:

• Lipids are non-polar and soluble in ethanol but insoluble in water; adding ethanol to aqueous sample dissolves them, and shaking emulsifies into cloudy suspension, confirming presence per solubility principles.

Why the others are wrong:

• A: Adds water and ethanol simultaneously to sample without proper dissolution sequence, leading to poor mixing.
• B: Includes unnecessary boiling, which can degrade sample without aiding emulsification.
• C: Reverses addition order (water to ethanol), preventing effective lipid dissolution if sample is in ethanol.

Final answer: D