I am wondering if the scientific control can be used as an uncountable noun.
For example,
One tube was used as control while the other received 0.1 pg/ml of PMA.
vs
One tube was used as the control while the other received 0.1 pg/ml of PMA.
The Oxford Learner's Dictionary lists the scientific control as countable, but I've seen it being used a lot as an uncountable noun. Examples from the ACAD section of COCA include:
eSNPs associated with nondifferential (FDR. 0.5) genes were used as control.
... and HUVEC (human umbilical vein endothelial cell line) were used as control.
Is is another of those usage vs. accuracy issues? Or is uncountable plain incorrect here?