What is a sample duplicate?

• A. A known quantity of analyte added to a sample for recovery assessment.
• B. A separate, independent sample collected for comparison.
• C. Replicate aliquots of the same sample taken through the entire analytical procedure.
• D. A blank used to detect contamination.

Answer: (C)

Sample duplicates are used to measure how consistent an assay is when the same material is analyzed more than once. It means taking replicate aliquots from the same sample and running them through the entire analytical procedure, from preparation to measurement. This tests precision because any variability you see between the duplicates reflects random errors in handling, extraction, instrument response, or analyst influence, rather than differences between samples. It differs from adding a known amount of analyte to a sample to test recovery, from collecting a separate independent sample for comparison, or from using a blank to check for contamination.