Larry, Darryl and Jenny are using a gas chromatograph to determine the identity of a chemical sample. They inject the sample into the machine and then wait to see how long it takes the chemicals in their sample to move from one end of a tube in the machine to the other end. They use this time to help them determine the identity of the chemical in the sample. Which of the following is an unavoidable error in this experiment?
1) The temperature of the machine
2) The size of the tube
3) The type of chemicals in the sample
4) The time it takes for the chemicals to move