What is the significance of the ‘royal blue’ tube?

The 'royal blue' tube is significant because it is specifically designed for trace metal analysis, a process that requires careful handling to avoid contamination. This tube often has a special coating or is manufactured in a way that minimizes the presence of trace elements, which can interfere with the results of tests measuring metals in the blood. The purity of the royal blue tube is crucial as even minute levels of contaminants can alter the results of tests assessing elements like lead, copper, or zinc.

Other options fail to capture the primary purpose of the royal blue tube. For instance, while shipping blood samples is an essential function in phlebotomy, it is not the intrinsic design purpose of the royal blue tube. Similarly, measuring blood volume is more related to specific collection tubes that address volume rather than trace contamination. Lastly, general chemistry testing utilizes tubes that are designed to hold a variety of analytes without the stringent requirement for avoiding contamination that the royal blue tube has. Thus, the correct answer highlights the unique function of the royal blue tube in maintaining the integrity needed for accurate trace metal testing.