Methods and kits for assaying a chemical in a sample are disclosed. The method includes placing an extraction solution and an internal standard in a container. A sample is collected from a first location and placed in the container. The container is transported to a second location where the chemical in the extraction solution is assayed. A kit for transporting the sample from a first location to a second location includes at least one container for holding the sample. The at least one container includes an extraction solution for dissolving a chemical in the solution and an internal standard for calibrating an assay of the chemical. The methods and kits may be used in a system for quantitating an amount of a sprout inhibitor on a tuber, such as a potato.