You can find more information concerning split specimens in several sections of this part:
§40.3-Definition.
§40.65-Quantity of split specimen.
§40.67-Directly observed test when split specimen is unavailable.
§§40.71-40.73-Collection process for split specimens.
§40.83-Laboratory accessioning of split specimens.
§40.99-Laboratory retention of split specimens.
§40.153-MRO notice to employees on tests of split specimen.
§§40.193 and 40.201 -MRO actions on insufficient or unavailable split specimens.
Appendix D to Part 40-Report format for split specimen failure to reconfirm.
49 C.F.R. § 40.189