Abstract: An autosampler includes a sample carrier for receiving first and second sets of sample containers each having a top end, a side wall, and a visible indicium on its side wall. The autosampler includes: an optical sensor to read the visible indicia and to generate a corresponding output signal; a controller to receive the output signal; and a sampling system to withdraw a sample. The sample carrier supports the first and second sets of sample containers at different heights such that the indicia of the sample containers of the second set are located above the top ends of the sample containers of the first set, whereby the indicia of the sample containers of the second set are exposed to the optical sensor over the top ends of the sample containers of the first set, thereby enabling the optical sensor to read the indicia of the second set of sample containers.