Serum zinc concentrations: contamination from laboratory equipment

Area of Science:

• Clinical Chemistry
• Trace Element Analysis
• Patient Nutrition

Background:

• Elevated serum zinc levels have been observed in patients undergoing total parenteral nutrition (TPN).
• The source of this elevation requires investigation to ensure accurate patient monitoring.

Purpose of the Study:

• To investigate the potential for sample collection materials to introduce zinc contamination.
• To identify specific collection tube components that contribute to elevated plasma zinc concentrations.

Main Methods:

• Blood samples were collected and divided into three groups: clean glass control tubes, vacuum collection tubes with rubber stoppers, and tubes containing a rubber stopper and clot activator.
• Plasma zinc concentrations were measured in samples from each collection method.

Main Results:

• Vacuum collection tubes with rubber stoppers introduced an average zinc contamination of 76 +/- 14 microgram/dl compared to glass controls.
• Tubes with both rubber stoppers and clot activators resulted in higher contamination, averaging 198 +/- 42 microgram/dl.

Conclusions:

• Standard blood collection methods, particularly those using rubber stoppers, can significantly contaminate plasma samples with zinc.
• Careful selection of blood collection containers is crucial for accurate trace element analysis, especially for plasma zinc concentrations.