Why would a standard solution to check accuracy with a colorimeter, spectrophotometer or test kit produce results of zero?
Accuracy check shows a result of zero
Be sure to add reagents to the standard, just as if it were a sample. Color needs to develop in the standard solution the same way that it develops in the sample.Follow the step-by-step procedure but substitute the standard solution for the sample. For example, add the standard to the sample cell, add reagents, wait any timed steps, and then read the standard in the kit or instrument.