Which method is preferred for storing samples to prevent contamination?

The preferred method for storing samples to prevent contamination is using brass or stainless steel tubes. These materials are non-reactive and do not leach chemicals into the samples, which minimizes the risk of contamination. Additionally, the closed design of these tubes protects the contents from external contaminants such as dust, moisture, and other environmental factors that could alter the integrity of the sample.

In contrast, the other options present various risks. Plastic containers with wide openings are more susceptible to contamination due to their design, allowing airborne particles to easily enter the container. Ceramic jars without lids expose the samples to contaminants from the air and surrounding environment, while open glass containers similarly provide no barrier to external contaminants, making them unsuitable for preserving sample integrity. Thus, brass or stainless steel tubes offer the best protection for samples against contamination.