New Developments of Laser Desorption Ionization Mass Spectrometry in Natural Products Research

Mass spectrometry (MS) represents an indispensable tool for the structural identification of natural products (NPs) and is one of the major focus areas of analytical chemistry research. The technique has long been used to obtain molecular weights and further molecular formulae. In the past, former ionization sources such as electronic impact (EI) limited MS analysis to predominately volatile, polar, and thermostable compounds. However, the development of soft ionization techniques such as electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), and laser desorption/ionization (LDI) have gradually extended the scope of MS analysis to a much wider range of chemical entities. Moreover, the hyphenation of liquid and gas chromatography with MS (LC‐MS, GC‐MS) has provided a most powerful tool for the analysis of complex mixtures and NPs. In fact, LC‐MS is often considered as a method of first choice particularly when studying complex mixtures of small molecules. On the other hand, recent developments in matrix‐assisted laser desorption/ionization (MALDI) and LDI may provide useful supplements and potential alternatives to this approach. Both methods share similar, though slightly different ionization mechanisms. While MALDI uses small molecules comprising strong UV chromophores (matrices) to transfer laser energy to the sample material, LDI targets compounds that can be directly ionized by laser irradiation without any matrix support. Moreover, certain compounds showing LDI properties may also work as MALDI matrices. With regard to NPs research, MALDI and LDI may help overcoming certain limitations encountered in LC‐MS such as the indispensable use of buffer solutions when analyzing alkaloids. Moreover, as (MA)LDI hardly requires any sample conditioning, analysis time can be significantly shortened. With all this in mind, the subsequent article will highlight some interesting MALDI and LDI applications, which focus on the detection of NPs in complex mixtures. This includes the use of specifically adapted matrices for the selective detection of alkaloids (i), the study of the inherent LDI and matrix properties of phenolic compounds (ii) as well of evaluation on the reproducibility of LDI signal patterns (iii). Eventually, a statistical approach toward LDI profiling, which may provide a future tool for quality control of large sample batches will be presented (iv)

New Developments of Laser Desorption Ionization Mass Spectrometry in Plant Analysis

The structural identification of natural products is one of the major focus areas of analytical chemistry research. Mass spectrometry (MS) has long been used to obtain molecular weights and further molecular formulae. In the past, former ionization sources such as electronic impact unfortunately limited MS analysis to predominately volatile, polar, and thermostable compounds. However, recent developments in soft ionization techniques such as electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), or laser desorption/ionization (LDI) have gradually extended MS analysis to a much wide range of chemical structures. As far as small natural compounds are concerned, LDI sources are still seldom used because of specific technical limitations. Indeed, the photoionization process of LDI is generally assisted by a matrix, which is a small molecule carrying strong UV chromophore. The process is then called matrix‐assisted laser desorption/ionization (MALDI) process. MALDI ionization therefore induces the formation of numerous matrix ions that commonly appear in the range 0–600 Da, and consequently interfere with molecular ions originating from many natural products. For this reason, the correct signal assignment is highly impaired in the critical region of interest. As LDI and MALDI are not only soft ionization processes but also quite sensitive techniques yielding high resolution spectra when coupled to a time‐of‐flight (TOF) analyzer, different attempts have been made to adapt these techniques for the analysis of natural products. Three of them will be more specifically discussed in this chapter: (i) LDI on neat gold surfaces obtained by physical vapor diffusion (PVD), (ii) desorption/ionization on self‐assembled monolayer surfaces (DIAMS), and (iii) the use of specific matrices for the selective detection of alkaloids

New Use for a Compound as a Matrix in the Specific Detection, Identification and/or Quantification of Alkaloids by MALDI-TOF Mass Spectrometry

The present invention relates to (i) a method of analysing small molecules that may have a mass of < 800 Da, in particular alkaloids, said method being generally referred to as MALDI-TOF-MS (or MALDI Time-of-Flight MAss Spectrometry) which is an acronym for a method of analysis by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry, to (ii) a molecule according to formula (I) and to the use thereof as a matrix in such an analysis method

Magnetization of carbon-coated ferromagnetic nanoclusters determined by electron holography

The magnetic properties of carbon-coated Co and Ni nanoparticles aligned in chains were determined using transmission electron holography. The measurements of the phase change of the electron wave due to the magnetization of the sample were performed. The ratio of remnant magnetization to bulk saturation magnetization Mr/Ms of Co decreased from 53% to 16% and of Ni decreased from 70% to 30% as the particle diameter increased from 25 to 90 nm. It was evident that the inhomogenous magnetic configurations could diminish the stray field of the particles. After being exposed to a 2-Tesla external magnetic field, the Mr/Ms of Co increased by 45% from the original values with the same dependency on the particle size. The Mr/Ms of Ni particles, on the other hand, increased only 10%. The increased magnetization could be attributed to the merging of small domains into larger ones after the exposure to the external magnetic field. The validity of the interpretation of the holograms was established by simulatio

Matrix for specific detection of alkaloids by MALDI-​TOF mass spectrometry

The présent invention relates to a novel bithiophenic matrix for spécifie détection of alkaloids by MALDI-TOF mass spectrometr

Photoluminescene properties of silicon nanocrystallites

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1996.Includes bibliographical references.by Arun A. Seraphin.Ph.D

Two new triterpenoid saponins from the leaves of Bupleurum lancifolium (Apiaceae)

Chemical investigation of the leaves of Bupleurum lancifolium led to the isolation and identification of two triterpenoid saponins previously undescribed named 3-O-[α-L-rhamnopyranosyl (1 → 4)-β-D-glucopyranosyl] echinocystic acid 28-O-β-D-glucopyranosyl ester (1) and 3-O-[α-L-rhamnopyranosyl (1 → 4)-β-D-glucopyranosyl] oleanolic acid 28-O-β-D-glucopyranosyl ester (2) along with the two known compounds isorhamnetin 3-rutinoside (3) and rutin (4). Their structures were elucidated by different spectroscopic methods, including HRESIMS analysis as well as 1D and 2D NMR experiments

New Developments of Laser Desorption Ionization Mass Spectrometry in Plant Analysis

The structural identification of natural products is one of the major focus areas of analytical chemistry research. Mass spectrometry (MS) has long been used to obtain molecular weights and further molecular formulae. In the past, former ionization sources such as electronic impact unfortunately limited MS analysis to predominately volatile, polar, and thermostable compounds. However, recent developments in soft ionization techniques such as electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), or laser desorption/ionization (LDI) have gradually extended MS analysis to a much wide range of chemical structures. As far as small natural compounds are concerned, LDI sources are still seldom used because of specific technical limitations. Indeed, the photoionization process of LDI is generally assisted by a matrix, which is a small molecule carrying strong UV chromophore. The process is then called matrix-assisted laser desorption/ionization (MALDI) process. MALDI ionization therefore induces the formation of numerous matrix ions that commonly appear in the range 0–600 Da, and consequently interfere with molecular ions originating from many natural products. For this reason, the correct signal assignment is highly impaired in the critical region of interest. As LDI and MALDI are not only soft ionization processes but also quite sensitive techniques yielding high resolution spectra when coupled to a time-of-flight (TOF) analyzer, different attempts have been made to adapt these techniques for the analysis of natural products. Three of them will be more specifically discussed in this chapter: (i) LDI on neat gold surfaces obtained by physical vapor diffusion (PVD), (ii) desorption/ionization on self-assembled monolayer surfaces (DIAMS), and (iii) the use of specific matrices for the selective detection of alkaloids