<p>High-Performance Liquid Chromatography (HPLC) is widely used in the pharmaceutical and fine chemical industries to establish chemical substance identity. HPLC is an analytical chromatographic technique, i.e., it is used to establish chemical substance identity and purity. Preparative chromatography is used to isolate usable quantities of chemical substances. A sample which gives rise to a chromatographic peak under specified conditions can be said to possess the property of containing the particular chemical substance to which that peak can be assigned. The chemical substance could be said to be part of the analysed sample in the mereological sense. A concern is raised by the possibility noted by Harré and Llored with respect to mereology, that it may be fallacious to infer that the substantive products of an analytical procedure are parts of the substance on which the procedure was performed. Instances arising from preparative chromatography show that that possibility exists, however, the value of analytical chromatography to chemical practice is that the chemical substances which are separated are considered as having being part of the sample analysed. Spatial and temporal aspects of chromatographic assignment of chemical substance properties are considered. A chromatographic peak could also be regarded as an ‘affordance’, i.e., arising from the interaction of the apparatus and the world. Consideration of chromatography in mereological terms is also discussed with relation to issues such as parthood, remainder and relation to concepts of purity, and the applicability of the concepts of fusion and disjointness.</p>