Forensic determination of pesticides in human serum using metal ferrites nanoparticles and SALDI-MS

A Surface Matrix of Au NPs Decorated Graphdiyne for Multifunctional Laser Desorption/Ionization Mass Spectrometry

The development of the valid strategy to enhance laser desorption/ionization efficiency gives rise to widespread concern in surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) technology. Herein, a hybrid of Au NP-decorated graphdiyne (Au/GDY) was fabricated and employed as the SALDI-MS matrix for the first time, and a mechanism based on photothermal and photochemical energy conversions was proposed to understand LDI processes. Given theoretical simulations and microstructure characterizations, it was revealed that the formation of a coupled thermal field and internal electric field endow the as-prepared Au/GDY matrix with superior desorption and ionization efficiency, respectively. Moreover, laser-induced matrix ablation introduced strain and defect level into the Au/GDY hybrid, suppressing the recombination of charge carriers and thereby facilitating analyte ionization. The optimized Au/GDY matrix allowed for reliable detection of trace sulfacetamide and visualization of exogenous/endogenous components in biological tissues. This work offers an integrated solution to promote LDI efficiency based on collaborative photothermal conversion and internal electric field, and may inspire the design of novel semiconductor-based surface matrices.

Continuous synthesis of BaFe2O4 and BaFe12O19 nanoparticles in a droplet microreactor for efficient detection of antihistamine drugs in oral fluid using surface-assisted laser desorption/ionization mass spectrometry

Surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) has received considerable attention as a complementary approach to matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), offering substantial potential for analyzing molecules in the low-mass region. Herein, we propose a facile method, a microreactor for the synthesis of two types of barium ferrite (BaFe2O4 and BaFe12O19) nanoparticles (NPs) within moving droplets for detecting antihistamine (AH) drugs in oral fluid (OF). The synthesized BaFe2O4 and BaFe12O19 NPs exhibited small particle size, good ultraviolet absorption, and excellent performance in SALDI-MS, as determined by survival yield measurements. The limits-of-detection for AH drugs were in the range of 1 pg mL-1 to 100 ng mL-1, and spot-spot reproducibility of the SALDI substrates was satisfactory. Moreover, when analyzing cetirizine in OF, the obtained recoveries of cetirizine were 101% and 99% using BaFe2O4 and BaFe12O19 NP, respectively. Furthermore, the proposed method was validated by analyzing OF samples from a healthy volunteer who consumed a 5 mg levocetirizine tablet for seven days. SALDI-MS analysis confirmed the successful detection of endogenous components, the parent ion of cetirizine, and other exogenous substances. This study reports an advanced application of droplet microreactor technology for designing and synthesizing a wide range of novel and efficient SALDI-MS substrates for various applications.

In Situ Self-Assembled Formation of Nitrogen-Rich Ag@Ti3C2 Film for Sensitive Detection and Spatial Imaging of Pesticides with Laser Desorption/Ionization Mass Spectrometry (LDI-MS)

Pesticide residues are hazardous to human health; thus, developing a rapid and sensitive method for pesticide detection is an urgent need. Herein, novel nitrogen-rich Ag@Ti₃C₂ (Ag@N-Ti₃C₂) was synthesized via an ecofriendly, ultraviolet-assisted strategy, followed by in situ formation of a highly homogeneous film on target carriers via a facile water evaporation-induced self-assembly process. Ag@N-Ti₃C₂ shows greater surface area, electrical conductivity, and thermal conductivity than Ti₃C₂. This Ag@N-Ti₃C₂ film overcomes the limitations of conventional matrixes and allows laser desorption/ionization mass spectrometry (LDI-MS) to provide fast and high-throughput analysis of pesticides (e.g., carbendazim, thiamethoxam, propoxur, dimethoate, malathion, and cypermethrin) with ultrahigh sensitivity (detection limits of 0.5-200 ng/L), enhanced reproducibility, extremely low background, and good salt tolerance. Furthermore, the levels of pesticides were quantified with a linear range of 0-4 μg/L (R² > 0.99). This Ag@N-Ti₃C₂ film was used for high-throughput analysis of pesticides spiked in traditional Chinese herbs and soft drink samples. Meanwhile, high-resolution Ag@N-Ti₃C₂ film-assisted LDI-MS imaging (LDI MSI) was used to successfully explore spatial distributions of xenobiotic pesticides and other endogenous small molecules (e.g., amino acids, saccharides, hormones, and saponin) in the roots of plants. This study presents the new Ag@N-Ti₃C₂ self-assembled film equably deposits on the ITO slides and provides a dual platform for pesticide monitoring and has the advantages of high conductivity, accuracy, simplicity, rapid analysis, minimal sample volume requirement, and an imaging function.

Aptamer-conjugated MoS2 for enrichment and direct detection of small molecules in laser desorption/ionization mass spectrometry

In this work, MoS₂ nanosheets were synthesized by the chemical exfoliation method and then modified with a thiol-terminated aptamer via a simple thiol functionalization route. The as-made nanomaterial was characterized by UV-vis absorption spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and transmission electron microscopy. By integrating the advantages of MoS₂ nanosheets and the recognition ability of aptamers, the functionalized nanomaterial has been successfully employed for simultaneous enrichment and analysis of sulfadimethoxine by matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS). The aptamer-conjugated MoS₂ showed an excellent capture ability to eliminate background signals from the species co-existing in a milk sample. The simplicity of the synthesis method and the excellent performance of aptamer-conjugated MoS₂ make it an ideal candidate for application in selective MS analysis of the target analyte from complex samples.

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 (NaBH4) and hydrazine monohydrate (N2H4·H2O), 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.

High-throughput screening and spatial profiling of low-mass pesticides using a novel Ti3C2 MXene nanowire (TMN) as MALDI MS matrix

Pesticides play critical roles in agricultural fields; however, pesticide residues can cause serious damage to human health and the ecological environment; therefore, developing a rapid and sensitive method for pesticide detection is urgently needed. Nanostructure-assisted matrix laser desorption/ionization (MALDI) mass spectrometry (MS) has great potential for the detection of low-mass pesticides. In this study, a novel Ti₃C₂ MXene nanowire (TMN) was prepared by a facile sol-gel method and served as a matrix to enhance MALDI MS performance in the analysis of pesticides in positive ion mode. The TMN showed superior performance in the high-throughput detection of six kinds of pesticides (organophosphorus, organochlorine, carbamate, neonicotinoids, triazole, and oxadiazines), with ultrahigh sensitivity (detection limits at sub-ppt levels), remarkable repeatability, excellent salt tolerance, and extremely low background compared to traditional organic matrices due to the specific polyaromatic structure and the doping of nitrogen. Furthermore, this matrix was successfully employed for the analysis of residual pesticides in traditional Chinese herbs, and the level of diniconazole was quantified with a linear range of 0-50 ng/mL (R² > 0.99). More importantly, the spatial distribution of various endogenous compounds (e.g., amino acids and saccharides, fatty acids, alkaloids, and plant hormones) and xenobiotic pesticides from the intact root of the medicinal plant P. quinquefolium was clearly visualized using the TMN self-assembly film as a matrix for MALDI imaging mass spectrometry (IMS). With superior advantages such as sensitivity, simplicity, rapidness, and minimal sample requirement, TMN as a matrix-assisted MALDI MS shows great promise for various applications.

Determination of Pesticides in Soybean Seeds Incorrectly Discarded Near a Spring of the Paranaíba River, GO-Brazil

The objective of this research was to evaluate the contamination of pesticides of carbamate and benzimidazole classes in soil, water and soybean seeds, incorrectly discarded near a spring in the state of Goiás-Brazil. The Solid-Liquid and Liquid-Liquid Extraction with Low Temperature Partition (SLE/LTP or LLE/LTP) methods were used for pesticide extraction and the analyses were performed by HPLC-UV. A high resolution mass spectrometer was used to confirm the identity of the compounds present in the seeds. The results showed that the soybeans were treated with the pesticide carbendazim and the dosage was three times higher than established by Brazilian legislation. In the soil and water analyzed there was no presence of the pesticides researched, nor of the carbendazim detected in the seeds. Since this was an environmental crime due to incorrect disposal, it is not known how long ago it occurred. Thus, depending on how long the seeds had been exposed there, the pesticide could have leached out, and caused contamination in the spring and soil. Thus, we conclude that the incorrect disposal of seeds treated with pesticides can be a risk to the permanence of life on the site.

Faster, better, and cheaper: harnessing microfluidics and mass spectrometry for biotechnology

High-throughput screening technologies are widely used for elucidating biological activities. These typically require trade-offs in assay specificity and sensitivity to achieve higher throughput. Microfluidic approaches enable rapid manipulation of small volumes and have found a wide range of applications in biotechnology providing improved control of reaction conditions, faster assays, and reduced reagent consumption. The integration of mass spectrometry with microfluidics has the potential to create high-throughput, sensitivity, and specificity assays. This review introduces the widely-used mass spectrometry ionization techniques that have been successfully integrated with microfluidics approaches such as continuous-flow system, microchip electrophoresis, droplet microfluidics, digital microfluidics, centrifugal microfluidics, and paper microfluidics. In addition, we discuss recent applications of microfluidics integrated with mass spectrometry in single-cell analysis, compound screening, and the study of microorganisms. Lastly, we provide future outlooks towards online coupling, improving the sensitivity and integration of multi-omics into a single platform.

Development of efficient SALDI substrate based on Au-TiO2 nanohybrids for environmental and forensic detection of dyes and NSAIDs

Herein, a matrix-free approach is presented for comprehensive environmental and forensic analysis of dyes and nonsteroidal anti-inflammatory drugs (NSAIDs) using Au-TiO₂ nanohybrids coupled with surface-assisted pulsed laser desorption ionization-mass spectrometry (SALDI-MS). The Au-TiO₂ nanohybrids was prepared and characterized using inductively coupled plasma-optical emission spectrometry (ICP-OES), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), surface area measurements, ultraviolet-visible (UV-vis) spectroscopy, transmission electron microscopy (TEM), and scanning electron microscopy-energy dispersive spectrometry (SEM-EDS). Initially, the optimal Au content was assessed using the survival yield (SY) method, confirming that 7.5% Au content on the TiO₂ surface offered the highest ionization efficiency. Subsequently, environmental analyses of dyes and NSAIDs in water samples were performed, and sensitive detection of all analytes was achieved with limits of detection (LODs) ranging from 10.0 ng mL^-1 to 10.0 fg mL^-1 and good spot-to-spot reproducibility. Additionally, the effect of potential contaminants commonly found in environmental samples, such as salts, surfactants and pesticides was also considered. Despite signal intensity reduction at high concentrations of some salts, the target analytes were detected, while the presence of surfactants and pesticides did not cause significant signal intensity reduction. Additionally, dyed and undyed Tetoron fibers and the effect of adhesive tape were evaluated. Direct analysis of the dyed Tetoron fibers on the target plate, using the nanohybrids, enabled higher detection sensitivity of the dyes, in addition to adducts of polystyrene and cellulose, the main components of the fiber. Finally, NSAIDs in oral fluid were analyzed and sensitive detection of the analytes was observed using the nanohybrids with LODs and LOQs in the range of 0.1-10 ng mL^-1 and 1-20 ng mL^-1, respectively. The trueness of the exact mass was in the range of 0.64-6.2 ppm while the recovery of the spiked samples was in the range of 82.90-107.54%% indicating the efficiency of the Au-TiO₂ nanohybrids as SALDI substrate. Thus, the Au-TiO₂ nanohybrids hold considerable promise in terms of sensitivity, reproducibility, and LOD, and may significantly contribute to environmental and forensic identification.

Clinical utility of validated gas chromatography-ion trap mass spectrometry in patients with anticholinesterase pesticides poisoning

Intentional or unintentional intake of anticholinesterase pesticides became common due to their extensive use in agricultural and domestic purposes, resulting in numerous poisoning cases. A simple, accurate, and sensitive gas chromatography-ion trap mass spectrometry-based method for the quantification of 12 anticholinesterase pesticides (monocrotophos, dimethoate, dichlorvos, azinphos-methyl, carbofuran, chlorpyrifos, dialifos, diazinon, malathion, parathion, methidathion, and terbufos) in serum was developed, and its utility in patients with alleged pesticides poisoning was assessed. The quantification was performed using liquid-liquid extraction by toluene/chloroform (4:1,v/v) with 500 μL of serum. On column limit of detection and limit of quantification were less than 50.00 μg/L. The recovery ranged from 97.54 to 103.23%. The calibration curves were linear (R² > 0.9937). Accuracy was found to be between - 7.1 and 7.2%. Intra-day and inter-day reproducibility was less than 17% for the spiked quality control serum samples. The level of pesticide in serum quantified by the validated method correlated with clinical signs and symptoms, pseudo-cholinesterase activity, total atropine dose, length of hospital stay, and clinical outcome in 15 patients with alleged pesticide poisoning. The validated method may be used for monitoring and prognosis in patients with pesticide poisoning and diagnosis of poisoning in forensic toxicology.