Examination of the physical properties of the xylenes (para, meta and ortho) indicates slightly different boiling points (138.4, 139.1, 144.4 degrees C respectively) but because these compounds are isomers, there is no difference in molecular masses. Therefore it is unlikely that a mass spectrometry detector will be able to discern any difference between the isomers, so there is no particular advantage to using the GC/MS. Instead, she takes the faster and easier route of using the GC with a packed column. She sets injector and detector temperatures to 150 degrees C (slightly above the boiling points). She sets the column temperature to 120 degrees C (a good rule of thumb when trying to separate compounds with similar boiling points) and injects 1 uL of the methanol solution. The result is one broad peak that is similar to the injection of the pure solvent (methanol) by itself. She injects standards of known concentrations of each xylene and discovers that the retention times of the xylenes are different enough to be resolved, but the solvent signal is so large that it is overlapping the retention times of the xylenes. What should she do?

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