# Chemical investigation of biological trace evidence; toxicological screening of waste residues obtained from DNA extraction processes

## TL;DR

This study shows how DNA extraction waste can also be used for toxicological analysis, allowing both genetic and chemical information to be obtained from small biological samples.

## Contribution

A novel method is proposed to perform toxicological screening on DNA extraction residues without compromising DNA analysis.

## Key findings

- Toxicological analysis was successfully performed on DNA extraction residues using HPLC-MS/MS.
- Molecules of interest were detected in two types of DNA extraction residues.
- The method was validated in a hypothetical case with successful identification of target molecules.

## Abstract

In a forensic scenario, if biological stains are found in very small quantities, these are usually collected for DNA analyses, considered essential for the forensic investigation and thus excluding possible investigations by other forensic disciplines as forensic toxicology. We developed an experimental study to evaluate the feasibility of analyzing DNA extraction residues obtained from DNA extraction procedures to perform toxicological analysis, with the aim to extract both genetic and toxicological information without affecting or compromising the genetic sample and/or DNA extraction. DNA extraction from four blood samples (fortified with 5 molecules of interest with a final concentrations of 1 µg/mL, 100 ng/mL, 10 ng/mL and 5 ng/mL, respectively) were analyzed with QIAGEN QIAmp® DNA Mini kit. Three waste residues collected from the DNA extraction were analyzed for the toxicological investigation via Solid-Phase Extraction and High-Performance Liquid Chromatography—Tandem Mass Spectrometry analyses (Thermo Scientific™ TSQ Fortis™ II Triple-Quadrupole Mass Spectrometer). The analytical investigation revealed that our analytes of interest were detected in two different residues of the DNA extraction procedure, allowing both genetic and toxicological analyses without affecting the DNA identification. At last, the experimental protocol was applied to a hypothetical case, with encouraging results and allowing the identification of our molecules of interest.