In drug testing using thin-layer chromatography, why is a volatile organic solvent mixed with urine specimens?

In drug testing using thin-layer chromatography, why is a volatile organic solvent mixed with urine specimens?

• A. To extract the drugs
• B. To stabilize the sample
• C. To color the spot
• D. To neutralize pH

Answer: (A)

In this context, the key idea is removing the drug from the urine matrix by extracting it into a volatile organic solvent. Urine is mostly water, and many drugs don’t stay well in that aqueous environment. Mixing the urine with an organic solvent lets the drug partition into the organic phase, separating it from many water‑soluble substances that could interfere with the TLC separation. Because the solvent is volatile, it can be easily evaporated after extraction, leaving a concentrated residue of the drug that can be spotted on the TLC plate for analysis. This extraction and concentration step is essential for clean, reliable separation on TLC. Stabilizing the sample, coloring the spot, or neutralizing the pH aren’t the primary purposes of adding this organic solvent in this procedure.

In this context, the key idea is removing the drug from the urine matrix by extracting it into a volatile organic solvent. Urine is mostly water, and many drugs don’t stay well in that aqueous environment. Mixing the urine with an organic solvent lets the drug partition into the organic phase, separating it from many water‑soluble substances that could interfere with the TLC separation. Because the solvent is volatile, it can be easily evaporated after extraction, leaving a concentrated residue of the drug that can be spotted on the TLC plate for analysis. This extraction and concentration step is essential for clean, reliable separation on TLC. Stabilizing the sample, coloring the spot, or neutralizing the pH aren’t the primary purposes of adding this organic solvent in this procedure.