Which of the following is not one of the characteristics of indirect coulometry [Koo-LOM-i-tree]?

W) Utilizes a constant current source and both indicating and generating electrodes

X) Can detect microgram amounts

Y) Requires the use of standards even if the current efficiency is known

Z) Can use unstable reagents
Y) REQUIRES THE USE OF STANDARDS EVEN IF THE CURRENT EFFICIENCY IS KNOWN