Ambient ionization is achieved by spraying from a carbon nanotube (CNT)-impregnated paper surface under the influence of small voltages (≥3 V). Organic molecules give simple high-quality mass spectra without fragmentation in the positive or negative ion modes. Conventional field ionization is ruled out, and it appears that field emission of microdroplets occurs. Microscopic examination of the CNT paper confirms that the nanoscale features at the paper surface are responsible for the high electric fields. Raman spectra imply substantial current flows in the nanotubes. The performance of this analytical method was demonstrated for a range of volatile and nonvolatile compounds and a variety of matrices. Low voltage: A carbon-nanotube-impregnated paper can be used to generate ions from organic molecules at potentials as low as 3 V. Common pesticides from the surface of an orange, ingredients of tablets, and a variety of analytes, such as amino acids, were characterized by this method. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Pradeep Thalappil

Department Of Chemistry

Depanjan Sarkar

Amino acids

chemical analysis

Electric fields

field emission

ionization

Mass spectrometry

Molecules

Raman spectroscopy

AMBIENT IONIZATIONS

High electric fields

IMPREGNATED PAPER

MOLECULAR IONIZATION

NANOSCALE FEATURES

NON-VOLATILE COMPOUNDS

Organic molecules

SPRAY IONIZATION

Carbon nanotubes

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Angewandte Chemie - International Edition

A new kind of ambient ionization method named superhydrophobic preconcentration paper spray ionization mass spectrometry (SHPPSI MS) is introduced, where superhydrophobicity and paper spray mass spectrometry (PS MS) are coupled. The SHPPSI MS requires only microliter amounts of analyte solutions, allows easy sampling procedure, and provides high sensitivity for a diverse array of analytes. It can be used to detect food adulteration at extremely low concentrations. The experimental methodology involves modifying one of the surfaces of a triangularly cut filter paper to make it acquire low surface energy by drop casting a green and ecofriendly superhydrophobic coating material over it followed by drying. A micrometer scale defect was made at close proximity to one of the tips of the paper using a pin. Preconcentration of the sample was accomplished by allowing a 10 μL droplet of an aqueous solution of the analyte to stand at the defect followed by drying naturally. The dried paper was used as the substrate for paper spray mass spectrometry by eluting the analyte with a suitable solvent. This novel technique was used to detect melamine in adulterated milk, whose detection at the ppt level in milk normally needs sophisticated instruments, a larger amount of sample, and a complex sampling procedure, including further purification and separation. The SHPPSI MS detects melamine directly from milk at the sub-ppb level by simply putting a microdroplet of adulterated milk at the substrate and eluting the sample with methanol. This paper-based technique can be a promising tool for direct sensing of analytes such as drugs in body fluids, pesticides in water and soil, etc. © 2019 American Chemical Society.

Analytical Chemistry

Sub-Parts-per-Trillion Level Detection of Analytes by Superhydrophobic Preconcentration Paper Spray Ionization Mass Spectrometry (SHPPSI MS)

A novel method of coupling electrochemistry (EC) with mass spectrometry (MS) is illustrated with a paper-based electrochemical cell supported by carbon nanotubes (CNTs). The electrochemically formed ions, created at appropriate electrochemical potentials, are ejected into the gas phase from the modified paper, without the application of additional potential. The electrochemical cell was fabricated by using a rectangular CNT-coated Whatman 42 filter paper with printed electrodes, using silver paste. This was used for studying the electrochemical conversion of thiols to disulfides, and the functionalization of polycyclic aromatic hydrocarbons (PAHs), which involve S-S and C-C bond formations, respectively. We also demonstrate the versatility of the set-up by utilizing it for the detection of radical cations of metallocenes, monitoring the oxidation of sulfides through the detection of reactive intermediates, and the detection of radical cations of PAHs, all of which occur at specific applied potentials. Finally, the applicability of this technique for qualitative and quantitative analyses of environmentally relevant molecules has been demonstrated by studying the electrochemical oxidation of glucose (Glu) to gluconic acid (GlcA) and saccharic acid (SacA). © 2019 The Royal Society of Chemistry.

Analyst

In situ monitoring of electrochemical reactions through CNT-assisted paper cell mass spectrometry

Materials are making inroads into mass spectrometry, and an example is the use of advanced materials for enhanced ionization by transformation of a less-ionizable molecule to an easily ionizable one. Here we show the use of Pt nanoparticle-decorated nanotubes as highly active catalysts for the reduction of 2,4,6-trinitrotoluene to 2,4,6-triaminotoluene and subsequent easy detection of the product by in situ ambient ionization mass spectrometry. © 2017 American Chemical Society.

Catalytic Paper Spray Ionization Mass Spectrometry with Metal Nanotubes and the Detection of 2,4,6-Trinitrotoluene

Fragile transition metal complex ions such as [Cr(H2O)4Cl2]+, difficult to be observed by gas-phase spectroscopy, are detected easily with carbon nanotube (CNT)-assisted low-voltage ambient ionization mass spectrometry. Observation of various substituted ions with D2O and ROH (R = CH3, C2H5, ...) established the versatility of the technique in detecting diverse species. Ligand substitution occurring in solution was captured by the low-voltage technique. The extreme softness of the technique coupled with nanoscale ion sources enabled the creation of such species. Analysis was extended to other halides as well. The intensity of these fragile ions gradually disappeared at voltages beyond 500 V and are completely absent in standard high-voltage ionization. Detection of inorganic complexes further enhances the scope of low-voltage ionization. (Figure Presented). © 2017 American Chemical Society.

Probing Coordination Complexes by Carbon Nanotube-Assisted Low-Voltage Paper Spray Ionization Mass Spectrometry

DESI MS, has been successfully employed for the analysis of molecules from a wide variety of surfaces without prior sample treatment. The efficiency of DESI MS relies on various parameters. However, those that critically affect the ionization of biological samples include: the solvent system and the sample or sample spotting surfaces. These parameters gain unequivocal dominance specially whilst dealing with sensitive and intricate biological samples. This review is meant to capture the attention of the DESI-MS researchers towards the crucial role of the solvent and sample spotting surfaces for successful biological DESI-MS. This review highlights these parameters as the backbone of the breakthroughs achieved in the analysis of biological materials of plant, bacterial, animal and human origins. © 2016 Elsevier B.V..

TrAC - Trends in Analytical Chemistry

Biological Desorption Electrospray Ionization Mass Spectrometry (DESI MS) - unequivocal role of crucial ionization factors, solvent system and substrates

Physical Review B

Optical redshift in the Raman scattering spectra of Fe-doped multiwalled carbon nanotubes: Experiment and theory

Electroanalysis

A Novel Hydrogen Peroxide Sensor Based on the Direct Electron Transfer of Catalase Immobilized on Nano-Sized NiO/MWCNTs Composite Film

Journal of Physics and Chemistry of Solids

Effect of plasma treatment on electrical conductivity and Raman spectra of carbon nanotubes

Ambient Sampling/Ionization Mass Spectrometry: Applications and Current Trends

Chemical Physics Letters

Field ionization using densely spaced arrays of nickel-tipped carbon nanotubes

Molecular ionization from carbon nanotube paper

Journal	Data powered by TypesetAngewandte Chemie - International Edition
Publisher	Data powered by TypesetWiley-VCH Verlag
ISSN	14337851
Open Access	No