Which mercury-containing fixative is used to preserve parasites in stool specimens?

Which mercury-containing fixative is used to preserve parasites in stool specimens?

• A. Formalin
• B. Sodium acetate
• C. Buffered glycerol
• D. Polyvinyl alcohol

Answer: (D)

The concept being tested is which fixative that contains mercury is used to preserve parasites in stool for accurate microscopic study. Mercury-based fixatives are valued because they lock in fine cellular details, especially nuclear morphology, that are crucial for identifying protozoa in stool samples. The mercury-containing option used for this purpose is Schaudinn's fixative, which includes mercuric chloride in an alcohol/formaldehyde solution. This combination preserves parasites very well and supports reliable staining and examination of trophozoites and cysts. The other substances listed are not mercury-containing. Formalin is formaldehyde in water and is a general fixative but does not include mercury. Sodium acetate is just a buffering salt, not a fixative. Buffered glycerol is used as a mounting medium or in some fixative formulations but does not contain mercury. Polyvinyl alcohol is a polymer used in some permanent slide preparations and mounting media, not a mercury-based fixative. So, the mercury-containing fixative used to preserve parasites in stool is Schaudinn's fixative.

The concept being tested is which fixative that contains mercury is used to preserve parasites in stool for accurate microscopic study. Mercury-based fixatives are valued because they lock in fine cellular details, especially nuclear morphology, that are crucial for identifying protozoa in stool samples.

The mercury-containing option used for this purpose is Schaudinn's fixative, which includes mercuric chloride in an alcohol/formaldehyde solution. This combination preserves parasites very well and supports reliable staining and examination of trophozoites and cysts.

The other substances listed are not mercury-containing. Formalin is formaldehyde in water and is a general fixative but does not include mercury. Sodium acetate is just a buffering salt, not a fixative. Buffered glycerol is used as a mounting medium or in some fixative formulations but does not contain mercury. Polyvinyl alcohol is a polymer used in some permanent slide preparations and mounting media, not a mercury-based fixative.

So, the mercury-containing fixative used to preserve parasites in stool is Schaudinn's fixative.