The syringe plunger contains trace elements due to the material; which elements are present?

• A. Cobalt and Chromium
• B. Zinc and Copper
• C. Selenium and Manganese
• D. Iron and Nickel

Answer: (A)

The test is asking you to recognize which trace metals are most likely contributed by the material of a syringe plunger. Syringe components are often made from stainless steel or chromium-containing alloys, and small amounts of alloying elements can leach into a solution drawn by the syringe. Chromium is a major element in stainless steels, providing corrosion resistance, and it can be present in trace amounts in the liquid being drawn. Cobalt is also found in some stainless steel grades and related alloys used for strength and durability, so a trace presence of cobalt alongside chromium is plausible from the plunger material.

The other pairs don’t fit as well with what syringe plungers are typically made from or expected to contaminate a sample. Zinc and copper are more characteristic of brass components, not the plunger itself; selenium and manganese aren’t the metals usually associated with standard syringe materials; iron and nickel are common in stainless steel, but the specific combination of cobalt and chromium is a better match for typical plunger alloys.

So, the presence of trace cobalt and chromium from the plunger material is the best match.