مجله دانش آزمایشگاهی ایران
سال پنجم شماره 4 (پیاپی 20، زمستان 1396)

Within this paper a sub-group of ambient ionization mass spectrometry namely direct ionization mass spectrometry techniques are reviewed. They are characterized by the generation of an electrospray directly from the sample investigated. Prominent representatives include paper spray mass spectrometry, tissue spray mass spectrometry, probe electrospray ionization or thin-layer chromatography mass spectrometry. Applications of all major direct ionization techniques within different fields such as biomedical analysis, analysis of natural products, analysis of technical products and food analysis

Atomic force microscope is a powerful tool to study and investigate a wide range of materials in nano-scale. Using this microscope, the study of physical and structural properties of materials such as roughness, hardness, topography and particle size is possible. Imaging of nano-particle particularly biological molecules is a capability of AFM that leads to extensive use of this technology in various fields of science. It is also able to manipulate the surfaces and particles.

Interaction of an accelerated electron beam with a sample target produces a variety of elastic and inelastic collisions between electrons and atoms within the sample. Elastic scattering changes the trajectory of the incoming beam electrons when they interact with a target sample without significant change in their kinetic energy. Backscattered electrons (BSE) are incident electrons reflected back from a target specimen by elastic scattering and imaged with scanning electron microscope (SEM). BSE detectors are typically placed above the sample in the sample chamber based on the scattering geometry relative to the incident beam often with separate components for simultaneous collection of back-scattered electrons in different directions. BSE detectors above the sample collect electrons scattered as a function of sample composition.

X-ray photoelectron spectroscopy (XPS) is an analytical technique that uses photoelectrons excited by X-ray radiation (usually Mg Kα or Al Kα) for the characterization of surfaces to a depth of 100 A°. Elemental identification and information on chemical bonding are derived from the measured electron energy and energy shifts, respectively. The use of ultrahigh vacuum (UHV) during analysis requires special sample handling. Depth profiling is possible using ion sputtering. Technological developments in electronics, nanotechnology, polymers, biotechnology, and medicine are all concerned with surfacerelated phenomena, suggesting sustained interest in XPS in the foreseeable future.