Question

Which of the following statements is true?

A. Most GC analytes present molecular weights over 800 Da
B. Samples analyzed by GC must be volatile enough to have a significant vapor pressure below around 250 C
C. Derivatizing analytes for GC analysis presents no practical problems and should not introduce quantitative errors
D. Temperatures in GC inlets can exceed 350 C, and thermally labile samples may decompose

Answer 1

The true statement is that samples for GC analysis must be volatile with significant vapor pressure below around 250°C. High temperatures in GC inlets can cause the thermal decomposition of sensitive samples. The option (B) is correct.

Step-by-step explanation:

The true statement among the options provided is Samples analyzed by GC must be volatile enough to have a significant vapor pressure below around 250°C. Gas chromatography (GC) requires that the analytes be volatile and able to vaporize at the temperatures provided by the GC equipment, typically not exceeding 250°C.

Statement A is false because most GC analytes have molecular weights well under 800 Da. Statement C is incorrect as derivatizing analytes for GC analysis can introduce quantitative errors if not carefully controlled. Lastly, statement D is generally true because the temperatures in GC inlets can exceed 350°C, and if the sample is thermally labile, it might decompose, leading to inaccuracies in analysis. Therefore, option (B) is correct.