*We report a multi-instrument characterization of the carbon particles in carbon/polymer/nanodiamond core-shell materials used for high-performance liquid chromatography. These particles are prepared by the carbonization/pyrolysis of poly(divinylbenzene) (PDVB) microspheres. Scanning electron microscopy showed that the particles (4.9 μm initially) decreased in size after air oxidation (to 4.4 μm) and again after carbonization (down to 3.5 μm) but remained highly spherical. Brunauer-Emmett-Teller measurements showed low surface areas initially (as received: 1.6 m 2 /g, after air oxidation: 2.6 m 2 /g) but high values after carbonization (445 m 2 /g). Fourier transform infrared spectroscopy revealed the changes in the functional groups after air oxidation (C = O and C-O stretches appear), carbonization (carbon-oxygen containing moieties disappear), and acid treatment (reintroduction of carbon-oxygen containing moieties). X-ray photoelectron spectroscopy (XPS) and elemental analysis revealed the surface and bulk oxygen contents before and after treatments. By XPS, the atom percent oxygen for the as received, air oxidized, carbonized, and acid treated particles are 8.7, 16.6, 3.7, and 13.8, respectively, and by elemental analysis, the percent oxygen in the materials is 0.6, 8.1, 0.9, 16.9, respectively. A principal components analysis of time-of-flight secondary ion mass spectrometry data identified ions that were enhanced in the different materials, where almost 90% of the variation in the analyzed peak areas was captured by two principle components. X-ray diffraction and Raman spectroscopy suggested that the carbonized PDVB was disordered. Thermogravimetric analysis showed significant differences between the differently treated PDVB microspheres. This work applies directly to a commercial product and the process for preparing it.