In this task, you are given a question and answer options for that question. Using this information, you have to classify each text into different topics: medicine, nursery, psychology, chemistry, pharmacology, biology.
Q: Question: Gas chromatography combined with mass spectrometry (GC-MS) is the most commonly used chromatographic coupled technique. The main difficulty of the coupling is in:
Options: <0> The analysis of molecular ions in the same place where they are generated. <1> The production of highly fragmented ions with accelerated electron generation. <2> The increase in the output flow rate of the chromatograph, which can not exceed nL / min. <3> The obtaining of the bidimensional spectrum that allows the separation in function of the relationship q / r. <4> The introduction into the high vacuum of the mass analyzer, of a compound that is at an atomospheric pressure.
A:
chemistry