**Core Concept**
The use of preservatives in chemical analysis is crucial to prevent contamination, degradation, or microbial growth during storage and handling of biological samples. Common preservatives include antifoaming agents, antimicrobial agents, and antioxidants.

**Why the Correct Answer is Right**
Preservatives are added to prevent unwanted reactions or degradation of the analyte. In the context of chemical analysis, preservatives are used to stabilize the sample and prevent changes in the sample's chemical composition. Some common preservatives include thimerosal, phenol, and formaldehyde. However, the use of certain preservatives may be restricted or avoided in specific types of analyses, such as those involving biological samples or certain types of chemical reactions.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because thimerosal is a common preservative used in chemical analysis, particularly in biological samples.
**Option C:** This option is incorrect because formaldehyde is a widely used preservative in chemical analysis, including in the preservation of biological samples.

**Clinical Pearl / High-Yield Fact**
When working with biological samples, it's essential to choose the right preservative to prevent contamination and degradation of the sample. Some common preservatives include thimerosal, phenol, and formaldehyde, but the choice of preservative will depend on the specific type of analysis and the sample being analyzed.

**Correct Answer:** D.