Nanotrap and Mass Analysis of Aromatic Molecules by Phenyl Group-Modified Nanoparticle

Laser-induced electron transfer desorption/ionization on MoO3 and WO3 surfaces for the determination of dithiocarbamates

Surface layers of molybdenum oxide MoO₃ and tungsten oxide WO₃ produced by thermal oxidation of molybdenum and tungsten plates in the air were studied for the first time as a platform for laser-induced electron transfer desorption/ionization. High analytical performance of such layers for the determination of metal complexes with dithiocarbamates, such as tetramethylthiuram disulfide, tetraethylthiuram disulfide, and diethyldithiocarbamate, has been demonstrated. All studied complexes are detected as radical cations, with no fragment ions. The ion yields from MoO₃ and WO₃ surfaces were found to be more than two orders of magnitude higher than those from nanocrystalline silicon surfaces. A novel method has been developed for the determination of trace amounts of dithiocarbamates based on the complexation of analytes with gold ions, followed by laser-induced electron transfer desorption/ionization. The limits of detection of dithiocarbamates were estimated to be about 1 ng/mL. The proposed method was successfully applied to the rapid screening of tetramethylthiuram disulfide residues in juice.

Nanoparticle-Assisted Laser Desorption/Ionization Mass Spectrometry (Nano-PALDI MS) with Py-Tag for the Analysis of Small Molecules

We compared two ionization methods, matrix assisted laser desorption/ionization (MALDI) and nanoparticle assisted laser desorption/ionization (Nano-PALDI) mass spectrometry (MS), for the analysis of amino acids derivatized with Py-Tag™ that consists pyrylium-based compound. Py-Tag is a useful stable derivatization reagent due to wide mass differences (using ¹³C as the sole stable labelling isotope). For Py-Tag labelled lysine, sensitive signals that showed less noise with a ten times higher sensitivity, showed a wider mass difference by Nano-PALDI MS compared to MALDI MS.

Preparation of phenyl-functionalized magnetic mesoporous silica microspheres for the fast separation and selective enrichment of phenyl-containing peptides

Peptide enrichment before mass spectrometry analysis is essential for large-scale peptidomic studies, but challenges still remain. Herein, magnetic mesoporous silica microspheres with phenyl group modified interior pore walls were prepared by a facile sol-gel coating strategy, and were successfully applied for selective enrichment of phenyl-containing peptides in complex biological samples. The newly prepared nanomaterials possessed abundant silanol groups in the exterior surface and numerous phenyl groups in the interior pore walls, as well as a large surface area (592.6 m² /g), large pore volume (0.33 cm³ /g), uniform mesopores (3.8 nm), strong magnetic response (29.3 emu/g), and good dispersibility in aqueous solution. As a result of the unique structural properties and size-exclusion effect, the core-shell phenyl-functionalized magnetic mesoporous silica microspheres exhibited excellent performance in fast separation and selective enrichment of phenyl-containing peptides, and the adsorption capacity for bradykinin reached 22.55 mg/g. In addition, selective enrichment of phenyl-containing peptides from complex samples that are consist of peptides, large proteins, and human serum were achieved by using the as-prepared microspheres, followed by high-performance liquid chromatography with ultraviolet detection and electrospray ionization quadrupole time-of-flight mass spectrometry analysis. These results demonstrated the as-prepared microspheres would be a potential candidate for endogenous phenyl-containing peptides enrichment and biomarkers discovery in peptidome analysis.

Sensitive Detection of Aromatic Hydrophobic Compounds in Water and Perfluorooctane Sulfonate in Human Serum by Surface-Assisted Laser Desorption/Ionization Mass Spectrometry (SALDI-MS) with Amine Functionalized Graphene-Coated Cobalt Nanoparticles

In this article, we describe the application of surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) with the use of amine functionalized graphene-coated cobalt nanoparticles (CoC-NH2 nanoparticles) to analyse aromatic hydrophobic compounds that are known environmental contaminants, including polycyclic aromatic hydrocarbons (PAHs) and pentachlorophenol (PCP). Our results demonstrated that SALDI-MS can detect PCP, anthracene, and pyrene in water. In particular, the CoC-NH2 nanoparticles proved to be an efficient means of capturing PCP in water because of the high adsorption capacity of the nanoparticles for PCP, which resulted in a detectability of 100 ppt. Furthermore, the CoC-NH2 nanoparticles also functioned as an adsorbent for solid-phase extraction of perfluorooctane sulfonate (PFOS) from human serum, displaying good performance with a detectability of 10 ppb by SALDI-MS.

Silver Oxide Based Nanoparticle Assisted Laser Desorption/Ionization Mass Spectrometry for the Detection of Low Molecular Weight Compounds

A specific property of silver oxide-based nanoparticles permits the ionization of an analyte, giving rise to various applications of a smart analytical methodology. The nanoparticles (d=6.7 nm) contained an Ag2O core. The detection of several model componds (a nucleobase and two hair growth promoters) via the use of silver oxide nanoparticles is described. Adducts were produced between the target molecules and the two silver stable isotopes (Ag(107) and Ag(109)), resulting in the formation of specific signals as well as a protonated signal. Thus, it was possible to easily determine whether the given signals were correlated with the target molecule or not.

Synthesis and Characterization of Functionalized Magnetic Nanoparticles for the Detection of Pesticide

We synthesized magnetic nanoparticles (MNPs) by mixing aqueous solutions of 3d transition metal chlorides (MCl2·nH2O) and a sodium metasilicate nonahydrate (Na2SiO3·9H2O) in order to produce monodispersed MNPs in a single step. The particle size can be controlled by adjusting the annealing temperature. We characterized the MNPs by X-ray diffraction (XRD), superconducting quantum interference device (SQUID), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), and zeta-potential measurement. Paramagnetic and superparamagnetic behaviors were found for the obtained samples depending on the particle size (d=3.0–4.6 nm). The synthesized MNPs could be modified with the amino-, phenyl-, and carboxy- groups on MNPs' surface by silanization procedure, respectively. The purpose of functionalizing the surface of the nanoscale magnetic particles was to realize subsequent capture and detection with desired other molecules by nanoparticle assisted laser ionization/desorption mass spectrometry.

Oligonucleotide analysis by nanoparticle-assisted laser desorption/ionization mass spectrometry

We analyzed oligonucleotides by nanoparticle-assisted laser desorption/ionization (nano-PALDI) mass spectrometry (MS). To this end, we prepared several kinds of nanoparticles (Cr-, Fe-, Mn-, Co-based) and optimized the nano-PALDI MS method to analyze the oligonucleotides. Iron oxide nanoparticles with diammonium hydrogen citrate were found to serve as an effective ionization-assisting reagent in MS. The mass spectra showed both [M - H](-) and [M + xMe(2+)- H](-) (Me: transition metal) peaks. The number of metal-adducted ion signals depended on the length of the oligonucleotide. This phenomenon was only observed using bivalent metal core nanoparticles, not with any other valency metal core nanoparticles. Our pilot study demonstrated that iron oxide nanoparticles could easily ionize samples such as chemical drugs and peptides as well as oligonucleotides without the aid of an oligonucleotide-specific chemical matrix (e.g., 3-hydroxypicolinic acid) used in conventional MS methods. These results suggested that iron-based nanoparticles may serve as the assisting material of ionization for genes and other biomolecules.

Steroid hormones analysis with surface-assisted laser desorption/ionization mass spectrometry using catechin-modified titanium dioxide nanoparticles

This paper describes the application of catechin-modified titanium dioxide nanoparticles (TiO(2) NPs) as matrices to analyze four steroid hormones by surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS). The catechin-modified TiO(2) NPs have high absorbance at 337 nm and are effective SALDI matrices when using a nitrogen laser. Four test steroid hormones-cortisone, hydrocortisone, progesterone, and testosterone-were directly analyzed by SALDI-MS. The limits of detection at a signal-to-noise ratio of 3 for cortisone, hydrocortisone, progesterone, and testosterone were 1.62, 0.70, 0.66, and 0.23 μM, respectively. This approach provides good quantitative linearity for the four analytes (R(2)>0.986) with good reproducibility (the shot-to-shot and batch-to-batch variations for the four analytes were less than 10% and 15%, respectively). We validated the practicality of this approach-considering its advantages in sensitivity, repeatability, rapidity, and simplicity-through the analysis of testosterone in a urine sample.