protective medium

例句：

1. 1. The protective medium is essential for the stability of the sample.
   保护介质对于样品的稳定性至关重要。
2. 2. In this experiment, the protective medium was used to prevent contamination.
   在这个实验中，使用了保护介质以防止污染。
3. 3. The protective medium was carefully mixed with the sample to ensure its homogeneity.
   保护介质被小心地与样本混合，以确保其均匀性。