SALDI Substrate-Based FeNi Magnetic Alloy Nanoparticles for Forensic Analysis of Poisons in Human Serum

In this study, FeNi magnetic alloy nanoparticles (MANPs) were employed for the forensic analysis of four poisons—dimethametryn, napropamide, thiodicarb, and strychnine—using surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS). FeNi MANPs were prepared via coprecipitation using two reducing agents, sodium borohydride (NaBH(4)) and hydrazine monohydrate (N(2)H(4)·H(2)O), to optimize the prepared MANPs and investigate their effect on the performance of SALDI-MS analysis. Thereafter, SALDI-MS analysis was carried out for the detection of three pesticides and a rodenticide. The prepared substrate offered sensitive detection of the targeted analytes with LOD values of 1 ng/mL, 100 pg/mL, 10 ng/mL, and 200 ng/mL for dimethametryn, napropamide, thiodicarb, and strychnine, respectively. The relative standard deviation (%RSD) values were in the range of 2.30–13.97% for the pesticides and 15–23.81% for strychnine, demonstrating the good spot-to-spot reproducibility of the FeNi substrate. Finally, the MANPs were successfully employed in the analysis of poison-spiked blood serum using a minute quantity of the sample with an LOD of 700 ng/mL dimethametryn and napropamide, 800 ng/mL thiodicarb, and 500 ng/mL strychnine. This study has great potential regarding the analysis of several poisons that may be found in human serum, which is significant in cases of self-harm.