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.

Question: When you want to analyze the volatile components of a liquid or solid sample by gas chromatography, a headspace methodology (HS-GC) is usually used. In its static form: 
 Options:  <0> An aerosol is generated on the solid samples by passing a gas flow over it, which causes the transfer of volatile compounds to it. After a while, a volume of this gas is introduced into the column. <1> It is used to analyze a liquid in contact with a gas, by injecting a small volume of liquid into the head of the column. <2> The sample is placed in a vial with a volume of gas above, closed and thermostatted. Once the equilibrium between the two phases is reached, an aliquot of gas is introduced into the stream of the carrier gas that goes to the column. <3> The sample in liquid form is placed in a vial and closed. After a while, the same is opened so that the volatile components are balanced with those of the environment and subsequently, a volume of the gas surrounding the chromatograph is introduced. <4> An extraction of the liquid or solid sample is carried out to a gas that flows on it continuously.
chemistry