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Emerging Biomedical Analysis
Published in Lawrence S. Chan, William C. Tang, Engineering-Medicine, 2019
The MALDI technique employs a matrix that transfers protons to large molecules by a laser source. Ionization by MALDI consists of three steps (Karas and Kruger 2003): In the first step, the analyte is mixed with the selected matrix material and transferred to a sample plate.In the second step, short laser pulses of UV or IR radiation is applied to the sample-matrix mixture for a few nanoseconds to trigger the desorption process, where the mixture plume leaves the surface at a velocity of several hundred m/s.In the final step, the analyte molecules are ionized by a proton transferred from the matrix during the desorption process.
Analysis of Pesticide Residues by Chromatographic Techniques Coupled with Mass Spectrometry
Published in José L. Tadeo, Analysis of Pesticides in Food and Environmental Samples, 2019
Wan Jing, Jin Maojun, Jae-Han Shim, A.M. Abd El-Aty
Laser desorption (LD) is an ionization method that uses a pulsed laser with a certain wavelength to irradiate and ionize the sample. The sample, placed on a substrate-coated target surface, is irradiated by the laser light. The substrate molecules absorb and transmit the laser energy, and ionize the sample molecules. The laser ionization source needs a suitable substrate to get a good ion yield. Therefore, this ionization source is often referred to as a matrix assisted laser desorption ionization (MALDI) source. MALDI is particularly suitable for time-of-flight mass spectrometers (TOFs). MALDI belongs to the category of soft ionization technology, mainly producing molecular ions, quasi-molecular ions, and fewer fragment ions and multi-charged ions. It is more suitable for the analysis of biological macromolecules. The common substrates used in MALDI are 2,5-dihydroxybenzoic acid, sinapic acid, nicotinic acid, and α-cyano-4-hydroxycinnamic acid.
Biomaterials and Surface Modification
Published in Mohammad E. Khosroshahi, Applications of Biophotonics and Nanobiomaterials in Biomedical Engineering, 2017
MALDI is a soft ionization technique used in mass spectrometry, allowing the analysis of biomolecules (biopolymers such as DNA, proteins, peptides, and sugars) and large organic molecules (such as polymers, dendrimers, and other macromolecules), which tend to be fragile and fragment when ionized by more conventional ionization methods. It is similar in character to electrospray ionization in that both techniques are relatively soft ways of obtaining ions of large molecules in the gas phase, though MALDI produces far fewer multiply charged ions. MALDI methodology is a three-step process: (i) the sample is mixed with a suitable matrix material and applied to a metal plate, (ii) a pulsed laser irradiates the sample, triggering ablation and desorption of the sample and matrix material, and (iii) the analyte molecules are ionized by being protonated or deprotonated in the hot plume of ablated gases, and can then be accelerated into whichever mass spectrometer is used to analyse them. An investigation was performed by Perera et al. (1995), which showed the formation of homo and hetro multimeric ions of large proteins in matrix assisted UV (337 nm) laser desorption/ionization of large proteins and their mixtures.
A hybrid process for 2,4-dichlorophenoxy acetic acid herbicidal treatment and its microbial identification by MALDI-TOF mass spectrometry
Published in Environmental Technology, 2020
Gamze Dogdu Okcu, Hatice Eser Okten, Arda Yalcuk
In published scientific literature, there are a limited number of reports the potential of coupled photocatalytic-biological treatment [8,12,15–17]. However, this is the first comprehensive study on the hybrid treatment of 2,4-D herbicide using a mixed-culture biofilm system and the detailed identification of bacterial isolates for all the biological systems. Matrix-assisted laser desorption/ionization, time of flight, mass spectrometry (MALDI-TOF/MS) is a method for determining the genus, species and even sub-species of bacterial isolates for the technique, chosen because of its basic sample preparation steps, low financial cost per analysis and rapid acquisition time [18]. In this work, firstly, the optimal time ratio was determined for the hybrid process by assessing degradation, oxidation and mineralization results of the 2,4-D; then the biodegradability of the residual 2,4-D solution was evaluated. Secondly, residual 2,4-D concentrations and chemical oxygen demand (COD) were analysed in three batch mode-operated biological reactors: aerated (A-BR), non-aerated (NA-BR) and hybrid reactors (P-B). Finally, MALDI-TOF-TOF/MS techniques were used to evaluate the impacts of 3 different bioreactors for 2,4-D degradation on the community structure before and after the biodegradation.