What is the color top of the tube used for testing ammonia?

The tube used for testing ammonia typically has a gray top. This color is associated with the use of sodium fluoride and potassium oxalate, which help preserve the sample and prevent metabolic changes that could affect the accuracy of ammonia levels. Ammonia is a sensitive analyte that can be quickly altered by metabolic processes, so using a tube with the appropriate additives is crucial for reliable results. The gray top tube's composition helps to stabilize the sample, ensuring that the results reflect the true ammonia levels at the time of collection.