Size Control of Carbon Spherical Shells for Sensitive Detection of Paracetamol in Sweat, Saliva, and Urine

We report on a facile strategy for separating carbon spherical shells (CSS) using centrifugation, with which shells were produced with diameter varying from 400 to 500 nm according to scanning and transmission electron microscopies. The shells were made of 79% carbon and 21% oxygen, and their surface was functionalized with carbonyl and hydroxyl groups. The CSS could form a homogeneous film on a glassy carbon (GC) electrode surface and be used in a sensing platform. In electroanalytical experiments, the sensitivity of the GC/CSS electrode for paracetamol increased with decreasing size of CSS. For 400 nm CSS, the sensitivity was 0.02 μA μmol–1 L, and the limit of detection and quantification in sweat, saliva, and urine samples was 120 and 400, 286 and 470, and 584 and 530 nmol L–1, respectively, which represents the highest performance among carbon-based sensors found in the literature. The GC/CSS electrodes were stable, robust against typical interferents, and allowed detection of paracetamol in sweat, saliva, and urine samples with a performance indistinguishable from conventional high-performance liquid chromatography.