Evaluation of blood impurity removal efficiency using the QuEChERS method.

Purpose: Comparison of the impurity removal efficiencies of the deproteinization and Quick, Easy, Cheap, Effective, Rugged, Safe (QuEChERS) methods, which are pretreatment methods for drug analysis adopted by many forensic autopsy institutions, was performed.

Method: Residual cardiac blood samples were pretreated using deproteinization and QuEChERS methods. The residual amounts of total proteins, total lipids, glucose, galactose, electrolytes, and inorganic elements were measured. We also compared the recovery rates and matrix factors when using liquid chromatography/tandem mass spectrometry (LC/MS/MS).

Results: The residual rates of total proteins, total lipids, glucose, galactose, and electrolytes using the deproteinization method were 16%, 75%, 75%, 90%, and 91%, respectively. In contrast, the QuEChERS method showed 1.1%, 11%, 7.6%, 9.4%, and 20%, respectively. The amounts of Mg and Mn in QuEChERS increased compared with those before treatment, but other inorganic elements remained at 9.6-89% during deproteinization and 0.30-17% in the QuEChERS. The recovery rate of metformin was low in QuEChERS; however, no differences were observed in the recovery rates or matrix factors of the other 16 drugs between deproteinization and QuEChERS.

Conclusions: This study quantitatively demonstrated that QuEChERS is extremely efficient at removing impurities from blood compared with deproteinization methods. QuEChERS has poor recovery rates for highly polar drugs but does not prevent their detection. The QuEChERS method is superior to the deproteinization method, considering the load of impurities on the analytical instruments.