Functionalized pyrolytic highly oriented graphite polymer film for surface-assisted laser desorption/ionization mass spectrometry in environmental analysis

Graphite Sheet-Assisted Laser Desorption Ionization-Mass Spectrometry for Small Organic Compound Analysis

Carbon-based nanopowders have been used as ionization materials for laser desorption ionization-mass spectrometry (LDI-MS) and are very efficient at detection in low m/z regions. In this study, we aimed to develop a new sheet-type graphite material that possessed a randomly grooved nanostructured surface consisting of developed sp2-conjugated atomic carbon to facilitate the desorption/ionization of small compounds in LDI-MS. The graphite sheet exhibited higher UV absorption and provided higher ionization efficiency and survival yield in the LDI-MS detection of a thermometer ion, 4-chloro-benzopyridinium, than those of highly oriented graphite plates. These properties demonstrate that the present graphite sheet is suited for use as an LDI-MS material. Graphite sheet-assisted LDI-MS successfully detected various substances, including amino acids, peptides, and polyethylene glycol polymers, with higher ion intensities and less noise than those associated with conventional organic matrix-assisted LDI-MS (MALDI-MS). Furthermore, graphite sheet-assisted LDI-MS analysis provided more peaks (252 peaks) derived from soy sauce than those obtained by MALDI-MS (36 peaks) and required fewer preparation processes (dilution and air-dried) compared with previously established graphite carbon black-assisted LDI-MS (171 peaks) in the positive mode. This study demonstrates that graphite sheet-assisted LDI-MS has the potential for small organic compound analyses in the biomedical and food science fields.

Organic matrix-free imaging mass spectrometry

Mass spectrometry (MS) is an ideal tool for analyzing multiple types of (bio)molecular information simultaneously in complex biological systems. In addition, MS provides structural information on targets, and can easily discriminate between true analytes and background. Therefore, imaging mass spectrometry (IMS) enables not only visualization of tissues to give positional information on targets but also allows for molecular analysis of targets by affording the molecular weights. Matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) MS is particularly effective and is generally used for IMS. However, the requirement for an organic matrix raises several limitations that get in the way of accurate and reliable images and hampers imaging of small molecules such as drugs and their metabolites. To overcome these problems, various organic matrix-free LDI IMS systems have been developed, mostly utilizing nanostructured surfaces and inorganic nanoparticles as an alternative to the organic matrix. This minireview highlights and focuses on the progress in organic matrix-free LDI IMS and briefly discusses the use of other IMS techniques such as desorption electrospray ionization, laser ablation electrospray ionization, and secondary ion mass spectrometry.

The influence of oxidative debris on the fragmentation and laser desorption/ionization process of graphene oxide derivatives

The influence of oxidative debris on laser desorption/ionization time of flight mass spectrometry (LDI-TOF-MS) analysis by using graphene oxide as a matrix was investigated to reveal its role in LDI process.

Applications of nanomaterials in mass spectrometry analysis

Mass spectrometry (MS) based analyses have received intense research interest in a series of rapidly developing disciplines. Although current MS techniques have enjoyed great successes, several key challenges still remain in practical applications, especially for the detection of biomolecules in biological systems. The use of nanomaterials in MS based analysis provides a promising approach due to their unique physical and chemical properties. In this review, nanomaterials with different compositions and nanostructures employed in MS applications are summarised and classified by their functions. Such an integrated and wide reaching review will provide a comprehensive handbook to researchers with various backgrounds working in this exciting interdisciplinary area.

Human serum albumin-modified Fe3O4 magnetic nanoparticles for affinity-SALDI-MS of small-molecule drugs in biological liquids

Here, we report on the use of human serum albumin (HSA)-modified Fe(3)O(4) nanoparticles (NPs) (HSA-Fe(3)O(4) NPs) for affinity-SALDI-MS of small drugs in human biological liquids. We demonstrated that HSA-Fe(3)O(4) NPs effectively captured small drugs from human urine and serum via the interactions between HSA and these drugs. The drugs adsorbed on HSA could then be identified by directly introducing the HSA-Fe(3)O(4) NPs into a mass spectrometer for SALDI-MS analysis. The ability of HSA to interact with multiple small drugs facilitated the simultaneous detection of a 4-drug-mixture in serum, viz., phenytoin, ibuprofen, camptothecin, and warfarin sodium, by affinity-SALDI-MS using HSA-Fe(3)O(4) NPs. In contrast, matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) with an organic matrix could detect only warfarin sodium. We also demonstrated the capacity of affinity-SALDI-MS to quantify warfarin sodium in urine samples across a range of 50 - 1000 μM (R(2) = 0.998) when using HSA-Fe(3)O(4) NPs. The detection sensitivity was further improved to a range of 5 - 100 μM (R(2) = 0.999) by using denatured HSA. The open structure of denatured HSA may enhance the effective extraction of small drugs from biological liquids, and increase the detection-sensitivity of affinity-SALDI-MS. Affinity-SALDI-MS using protein-modified Fe(3)O(4) NPs can open up new approaches to the analytical detection of small drugs in biological liquids by SALDI-MS.

Functionalized graphene-coated cobalt nanoparticles for highly efficient surface-assisted laser desorption/ionization mass spectrometry analysis

Graphene-coated cobalt nanoparticles surface-functionalized with benzylamine groups (CoC-NH(2) nanomagnets) were shown to effectively enrich analytes for surface-assisted laser desorption/ionization mass spectrometry (affinity SALDI-MS) analysis. These CoC-NH(2) nanomagnets are highly suited for use with affinity SALDI-MS because their mean diameter of 30 nm, high specific surface area of 15 m(2) g(-1), and high-strength saturation magnetization of 158 emu g(-1) led to efficient extraction of analytes by magnetic separation, which in turn enabled excellent SALDI-MS performance. Surface modification of CoC nanomagnets with benzylamine groups increased the yield of peptide ions and decreased fragmentation of benzylpyridinium ions, so-called "thermometer ions" formed through soft ionization. The CoC-NH(2) nanomagnets were used to extract perfluorooctanesulfonate from large volumes of aqueous solutions by magnetic separation, which was identified directly by SALDI-MS analysis with high sensitivity even at the sub-part-per-trillion level (∼0.1 ng/L). The applicability of CoC-NH(2) nanomagnets in conjunction with SALDI-MS for the enrichment and detection of pentachlorophenol, bisphenol A, and polyfluorinated compounds (PFCs) with varying chain length, which are environmentally significant compounds, as well as small drugs, was also evaluated.

Nanocomposites as novel surfaces for laser desorption ionizationmass spectrometry

The possibility to utilize nanocomposite films as easy-to-handle surfaces for surface assisted laser desorption ionization-mass spectrometry (SALDI-MS) of small molecules, such as pharmaceutical compounds, was evaluated. The signal-to-noise values of acebutolol, propranolol and carbamazepine obtained on the nanocomposite surfaces were higher than the values obtained on plain PLA surface showing that the nanoparticles participate in the ionization/desorption process even when they are immobilized in the polymer matrix. The advantages of nanocomposite films compared to the free nanoparticles used in earlier studies are the ease of handling and reduction of instrument contamination since the particles are immobilized into the polymer matrix. Eight inorganic nanoparticles, titanium dioxide, silicon dioxide, magnesium oxide, hydroxyapatite, montmorillonite nanoclay, halloysite nanoclay, silicon nitride and graphitized carbon black at different concentrations were solution casted to films with polylactide (PLA). There were large differences in signal intensities depending on the type of drug, type of nanoparticle and the concentration of nanoparticles. Polylactide with 10% titanium oxide or 10% silicon nitride functioned best as SALDI-MS surfaces. The limit of detection (LOD) for the study was ranging from 1.7 ppm up to 56.3 ppm and the signal to noise relative standard deviations for the surface containing 10% silicon nitride was approximately 20-30%. Scanning electron microscopy demonstrated in most cases a good distribution of the nanoparticles in the polymer matrix and contact angle measurements showed increasing hydrophobicity when the nanoparticle concentration was increased, which could influence the desorption and ionization. Overall, the results show that nanocomposite films have potential as surfaces for SALDI-MS analysis of small molecules.