Final answer:
In the context of ETS tubes for chemistry tests, the gray stopper is used for tubes with anticoagulants like potassium oxalate and glucose preservatives like sodium fluoride, ensuring accurate blood glucose measurements.
Step-by-step explanation:
The gray stopper color for an ETS tube is typically used to identify tubes containing additives for glucose preservation and stabilization, such as sodium fluoride and potassium oxalate combination. The anticoagulant potassium oxalate prevents coagulation by binding calcium, while sodium fluoride inhibits glycolysis, the process where glucose is used by cells, ensuring that glucose levels remain stable during storage and transport of the blood sample for chemistry tests. The use of these anticoagulants is critical in obtaining accurate measurements of blood glucose and other chemistry tests.
While the specific details given in the question refer to the extraction and quenching of samples for testing gabapentin and gabapentin enacarbil, the use of such tubes is fundamental in pre-analytical sample preparation across various tests.