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.

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

Pesticides can have harmful effects on the environment and on humans, resulting in acute, or in some cases, fatal poisoning. Pesticides are inexpensive, easily accessible, and commonly linked to forensic investigations involving suicide or attempted suicide. Pesticide exposure is monitored by determining the presence of the pesticide (or its metabolites) in biological samples, such as blood serum. Traditional methods require the use of a large sample volume and extensive sample preparation to confirm the presence of such harmful materials. Thus, owing to their unique physico-chemical properties, metal ferrites nanoparticles (NPs) were developed as assisting agents in surface-assisted laser desorption/ionization mass-spectrometry (SALDI-MS) for detecting pesticides in human blood serum. Specifically, ZnFe2O4, MnFe2O4, and CuFe2O4 NPs were synthesized using co-precipitation method and were characterized using different analytical techniques, including X-ray diffraction, UV-vis spectroscopy, X-ray photo-electron spectroscopy, transmission electron microscopy, and the Brunauer-Emmett-Teller method. First, it was shown that the integration of metal ferrites NPs in the SALDI technique enabled sensitive detection towards fatty acids used as model analytes with the limit-of-detection (LOD) in the range of 10 µg mL-1 to 1 fg mL-1. Additionally, the extent of internal energy transfer was evaluated for the ZnFe2O4, MnFe2O4, and CuFe2O4 NPs using the survival yield (SY) method with benzylpyridinium (BP) as the chemical thermometer. The obtained SY values were 0.95, 0.94, and 0.88 for ZnFe2O4, MnFe2O4, and CuFe2O4 NPs, respectively; this indicated the higher degree of internal energy transfer of CuFe2O4 NPs. Finally, CuFe2O4 NPs were utilized to probe human serum spiked with different pesticides using a small sample volume and minimal sample pretreatment. The findings confirmed the successful detection of napropamide, metalaxyl, and pestanal with satisfactory reproducibility and LODs of 10 µg mL-1, 10 ng mL-1, and 100 pg mL-1, respectively. Thus, the development of the high-efficiency SALDI technique will enable its use as an analytical tool in forensic investigation using minute volumes of sample and substrate and with minimum sample handling.

Magnetic nanocomposite-based SELDI probe for extraction and detection of drugs, amino acids and fatty acids.

The use of carbon black-Fe3O4 magnetic nanocomposite (CB-Fe3O4) as a probe for surface-enhanced laser desorption ionization mass spectrometry (SELDI-MS) with a high extraction efficiency and sensitive detection is described. The magnetic nanocomposite was synthesized and fully characterized using X-ray photoelectron spectroscopy, X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, Ultraviolet-Visible spectroscopy, transmission electron microscopy and nitrogen sorption. The feasibility of the SELDI probe to extract and detect three classes of drugs (labetalol, metoprolol, doxepin, desipramine, triprolidine and methapyrilene) spiked in wine is demonstrated. All the drugs were successfully and reproducibly extracted and detected with high efficiency and with limits of detection (LOD) between 1 and 1000 pg mL-1. The adsorption capacity of the nanocomposite for the drugs was evaluated by UV-Vis spectroscopy. The results showed that 27.8-36.1% of the drugs were adsorbed on the magnetic probe within 3 min. The nanocomposite was also applied for efficient analysis of amino acids and fatty acids. Both types of analytes can be extracted within a few minutes and then successfully quantified by SELDI-MS. Graphical abstract A schematic presentation of carbon black-Fe3O4 magnetic probe for SELDI analysis of small molecules. The probe containing the analyte(s) is collected with the aid of a magnet and deposited on the target plate for mass spectrometry analysis.