electric charge, Q

https://dx.doi.org/10.1351/goldbook.E01923
Integral of the electric current over time. The smallest electric charge found on its own is the elementary charge, e, the charge of a proton.
Source:
PAC, 1996, 68, 957 (Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)) on page 970