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Emerging Biomedical Analysis
Published in Lawrence S. Chan, William C. Tang, Engineering-Medicine, 2019
Many variants of ESI have been developed in recent years. Ambient ionization is a family of techniques that was derived from ESI to enable rapid MS analysis at lower cost. Ambient ionization techniques generate ions under ambient conditions for subsequent MS analysis directly on the sample with minimum sample preparation (Cooks et al. 2006, Nyadong et al. 2007). Representative ambient ionization techniques are desorption electrospray ionization (DESI) and direct analysis in real time (DART). In the DESI technique, an electrospray of charged solvent droplets hits the sample surface and extracts analyte molecules to form secondary droplets (Fig. 2). The secondary droplets undergo a similar ionization process with ESI and eventually are delivered to the inlet of a mass spectrometer (Takats et al. 2004). In the DART methodology, an electrical potential is applied to a helium gas stream to generate metastable species. These excited-state gas molecules subsequently react with the analyte surface to form ions (Cody et al. 2005). Due to the simple and cost-effective experimental setup, DESI, DART and other ambient ionization techniques, such as paper spray ionization, liquid microjunction surface sampling probe (LMJ-SSP) and rapid evaporative ionization mass spectrometry (REIMS), were used in several clinical studies (Li et al. 2017). Examples of clinical applications of ambient ionization MS will be discussed later in this chapter.
Thin Layer Chromatography
Published in Grinberg Nelu, Rodriguez Sonia, Ewing’s Analytical Instrumentation Handbook, Fourth Edition, 2019
Łukasz Cieśla, Monika Waksmundzka-Hajnos, Joseph Sherma
The on-line TLC–MS solutions are further subdivided into vacuum-based spectrometry and ambient ionization mass spectrometry approaches. The following vacuum-based desorption/ionization techniques have been applied in direct sampling TLC–MS: fast atom bombardment (FAB), liquid secondary ion mass spectrometry (LSIMS), laser desorption/ionization (LDI), matrix-assisted laser desorption/ionization (MALDI), and surface assisted laser desorption/ionization (SALDI) (Cheng et al., 2011). The development of atmospheric pressure ionization MS can be considered as another step ahead in the development of TLC–MS hyphenation. In atmospheric pressure techniques, the TLC plate does not have to be placed in a vacuum chamber for ionization. The following techniques have been applied for the ambient ionizing of compounds adsorbed on solid surfaces: laser desorption/atmospheric pressure chemical ionization (LD/APCI), laser ablation inductively coupled plasma (LA-ICP), desorption electrospray ionization (DESI), direct analysis in real time (DART), electrospray laser desorption ionization (ELDI), and laser-induced acoustic desorption/electrospray ionization (LIAD/ESI) (Cieśla and Kowalska, 2013).
Basics Of Gas Chromatography Mass Spectrometry System
Published in Raquel Cumeras, Xavier Correig, Volatile organic compound analysis in biomedical diagnosis applications, 2018
William Hon Kit Cheung, Raquel Cumeras
There are multiple names given for this analytical technique, Direct Analysis in Real Time (DART) (Beckman, 2008; Fuhrer, 2011) or Direct Injection Mass spectrometry (DIMS), but the principle is the same; the sample is introduced into the MS system through the use of electrospray ionization interface without any form of chromatographic separation applied, and the entire mass spectrum of the sample is measured and recorded. This is a high-throughput low-level chemical information fingerprinting approach; since no chromatographic separation is applied the complexity of the mixture is not reduced. In DART/DIMS analysis, the effect of ion suppression is significant since the entire sample is being ionized at the same time. If the sample matrix is complex in nature, low abundance ions would likely to be missed due to heterogeneous ionization effect.
Detection of RDX traces at the surface with sonic aerosol flow desorption
Published in Aerosol Science and Technology, 2018
Viktor V. Pervukhin, Yuri N. Kolomiets
The search for ways to simplify the preparation of samples led to the development of a number of methods, commonly called ambient mass spectrometry (Monge et al. 2013). These methods, in which analyte ions are formed by the action of charged droplets, particles, ions, or metastable atoms on the surface, include: Desorption Electrospray Ionization (DESI, Cotte-Rodriguez et al., 2005; Cotte-Rodríguez and Cooks 2006; Takáts et al. 2005; Justes et al. 2007), Direct Analysis in Real Time (DART, Petucci et al. 2007; Cody, Laramée, and Durst 2005), and Desorption Atmospheric Pressure Chemical Ionization (DAPCI, Chen et al. 2007). The methods have a great potential for analyzing surfaces, as they bypass the stage of sample preparation. However, since the MS is used as an analyzer, the methods become expensive and not always applicable in the field. On the other hand, the DESI simulation shows that the hydrodynamic forces play an important role in the desorption of the analyte from the surfaces in this process (Costa and Cooks 2008). Therefore, it seems reasonable to separate desorption and analysis in this case. Such approach allows collecting microparticles without manual sampling and using a simple device for analysis (e.g., gas chromatograph).
Acceleration of the thermal decomposition of RDX in microdroplets investigated by aerodynamic thermal breakup droplet ionization mass spectrometry
Published in Aerosol Science and Technology, 2020
Viktor V. Pervukhin, Dmitriy G. Sheven
Hexogen (RDX, 1,3,5-trinitro-1,3,5-triazacyclohexane) is an explosive that is widely used both for military and civilian purposes (for example, its derivatives are important components of various solid fuels). Although RDX is quite stable during storage (Sisco et al. 2017), it is toxic and carcinogenic (Robidoux et al. 2000; White and Claxton 2004), thus, the widespread use of the RDX results in the pollution of the soil and groundwater (Astratov et al. 1997; Beller and Tiemeier 2002). Considering the above-mentioned circumstances, the effective methods for RDX detection are needed. In particular, many works are focused on the decomposition of RDX as well as RDX based explosive mixtures in the environment or during the application (Sisco et al. 2015; Liebman et al. 1987; Snyder et al. 1989; Miller and Garroway 2001; Xiao et al. 2018; Yan et al. 2019). Thus, the possibility to accelerate RDX degradation of RDX (investigated in this work) is in great importance considering the problem of environment pollution. Mass spectrometry (MS) is the preferred analytical method for characterization since it is highly selective. In MS analysis, various methods of ionization can be used, such as electrospray ionization (ESI-MS) (DeTata, Collins, and McKinley 2013; Berset et al. 2008), chemical atmospheric pressure ionization (APCI) (Ewing, Atkinson, and Clowers 2013) or Direct Analysis in Real Time (DART) technique (Sisco, Dake, and Bridge 2013; Bridoux et al. 2016). However, the RDX ionization at ambient pressure gives rather complex mass spectra with several RDX related ions. Also, under the same conditions, the relative ion content varies significantly depending on the impurities, the contamination of the system, and the concentration of the analyte (for example, in the liquid chromatography/mass spectrometry experiments LC/MS) (Gapeev, Sigman, and Yinon 2003).