Luciferin-containing substrates are provided including a substrate and luciferin dried on the substrate. The luciferin-containing substrate is free of a detectable amount of reactive luciferase. The substrate is optionally a nonwoven substrate. Monitoring devices are also provided. The monitoring devices include a test element having a test portion, a detection reagent comprising luciferase, a luciferin-containing substrate, and a container having a first end with an opening and a second end opposite the first end. The container is configured to receive the test portion and configured to be operationally coupled to an analytical instrument. The detection reagent and the luciferin each are capable of participating in one or more chemical reaction that results in the formation of a detectable product.