Supplementary information files for A direct analysis method using Sheath Flow Probe Electrospray Ionization-Mass Spectrometry (sfPESI-MS) to detect drug residues from forensic gel lifts

Latent fingerprints at crime scenes are frequently recovered using forensic gel-lifters, which can help to preserve the crime scene and to enhance visualization of traces such as blood or paint. In addition to providing fingerprint ridge detail, additional chemical information can also be recovered from gel lifts that may prove pertinent to an investigation. However, while DNA and metal ions have been shown to be able to be detected in gel lifted fingerprints, the determination of other types of chemical information such as the presence of drugs in gel lifted prints has not been previously shown.This study demonstrates the application of an ambient ionisation method, sheath flow probe electrospray ionisation-mass spectrometry (sfPESI-MS) to the direct analysis of gel lifted fingerprints. A model drug compound (zolpidem) is successfully detected from gel lifted prints from 3 different surface types, glass, metal and paper. The surface activity-based separation associated with probe electrospray approaches is shown to resolve zolpidem ions from background phthalate species, significantly enhancing the response obtained from the gel-lifter. A depletion series experiment shows that the drug residue can be detected with up to 100 % efficiency after 8 consecutive contacts, however detection efficiency drops to 20 % after 30 contacts. The developed approach has potential application to analysis of historical gel-lifters to obtain additional chemical information.

犯罪现场的潜指纹（latent fingerprints）常通过法医凝胶提取剂（forensic gel-lifters）提取，该工具既能保护犯罪现场，又可增强血液、油漆等痕迹的可视化效果。除获取指纹嵴线细节（fingerprint ridge detail）外，凝胶提取样本（gel lifts）还可提供额外化学信息，这类信息或与案件调查密切相关。尽管已有研究证实可在凝胶提取的指纹中检测到DNA与金属离子，但此前尚未有研究报道可通过凝胶提取指纹检测药物等其他类型的化学物质。本研究将鞘流探针电喷雾电离-质谱（sheath flow probe electrospray ionisation-mass spectrometry，sfPESI-MS）这一常压电离技术（ambient ionisation method）用于凝胶提取指纹的直接分析。研究人员成功在玻璃、金属、纸张三种不同载体表面的凝胶提取指纹中，检测到模型药物化合物唑吡坦（zolpidem）。研究显示，探针电喷雾技术所具备的基于表面活性的分离能力，可将唑吡坦离子与背景中的邻苯二甲酸盐类杂质（phthalate species）有效分离，显著提升了凝胶提取剂的检测信号响应。耗竭系列实验结果表明，经连续8次接触后，仍可实现100%的药物残留检测效率；但当接触次数增至30次时，检测效率降至20%。本研究所开发的分析方法，有望应用于历史凝胶提取样本的分析，以获取更多额外的化学信息。