A larger peak after sample preparation can reflect either more analyte reaching the instrument or a stronger instrument response to the same amount. Westland and Dormann examined that distinction while applying QuEChERS preparation to benzodiazepines in blood and urine.
The researchers observed increased apparent recoveries with external and internal standard quantification. They used standard addition, which adds known analyte amounts to the sample matrix, to investigate the stronger response. Their results supported matrix enhancement as an explanation. Components carried through preparation can alter how a compound responds during analysis, even when the amount originally in the sample is unchanged.
Ask how the lab evaluated extraction recovery separately from instrument response. Compare the calibration matrix, internal standard behavior and validation data for the particular drug. The study used GC–MS and raised questions about how the approach compares with LC–MS/MS workflows. Its results do not establish a universal recovery improvement across matrices or instruments.