Spray drying electrospraying

There are also other methods such as spray pyrolysis and electrospray pyrolysis besides the above method [26]. To prepare nanoparticles by spray pyrolysis, a starting solution is prepared by dissolving, usually, the metal salt of the product in the solvent. The droplets atomized from a starting solution are introduced to furnace. Drying, evaporation of solvent, diffusion of solute, precipitation, reaction of precursor, and surrounding gas, pyrolysis may occur inside the furnace before the formation of product. It is similar to spray drying except the type of precursor. For this, colloidal particles are typically used as precursors. Some products prepared by spray pyrolysis are listed in Table 34.1. 

Electroencapsulation is an application of electrospraying in which liquid is atomized into micro- or even nanosized droplets using electrostatic forces alone. The method allows better controllability of the capsulation process than, e.g., the most commonly used spray drying. Due to the applied electrostatic forces, it also enables production of complex capsule structures, like solid shell covered liquid core particles. In this review, we will focus on electroencapsulation processes used to improve the handling, processing, and administration of porous silicon-based drug delivery systems. 

Electro-coextrusion 2 Electroencapsulation 2 Electrospraying 1 Electrostatic forces 1 Oral delivery 1 Spray drying 1, 3... 

Figure 4. Ion source and reaction chamber for ion-molecule equilibria. Solution to be electrosprayed flows through elestrospray capillary ESC at 1 -2 pL/min. Spray and ions enter pressure reduction capillary PRC and emerge into forechamber FCH maintained at 10 torr by pump PL. Ions in gas jet, which exits PRC, drift towards interface plate IN under influence of drift field imposed between FCH and IN. Ions enter the reaction chamber RCH through an orifice in IN and can react with reagents in the reagent gas mixture RG. This flows into RCH and out of RCH to FCH where it is pumped away. Ions leaking out of RCH through orifice OR are detected with a mass spectrometer. To reduce the inflow of solvent vapors into the pressure reduction capillary PRC, a stream of dry air is directed through the pipe Al, at 60 L/min, and pure N2 is directed at SG into the annular space at the entrance of the pressure reduction capillary, PRC. From Klassen, J. S. Blades, A. T. Kebarle, P. J. Phys. Chem. 1995, 99, 1509, with permission.

GC/MS with capillary columns has been the gold standard for more than 20 years, but LC/MS has become a complementary method due to the success in interface development with atmospheric pressure ionisation (API) for low molecular weight compounds and the appHcation to biopolymers. For many areas of analytical chemistry, LC/MS has become indispensible due to its advantages over GC/MS for polar and thermolabile analytes. A Hmiting factor for LC/MS has been the incompatibility between the hquid eluting from the LC and the mass spectrometer vacuum. This could be overcome in electrospray ionisation with the use of a nebuliser gas ( ion spray ) or additional heated drying gas ( turbo ion spray ) (70, 71]. Due to its high sensitivity and selectivity, APl-MS has become a standard tool for the stracture elucidation of analytes from complex mixtures. 

Electrospray ionisation generates analyte ions this is accomplished by spraying the eluent (mobile phase solvent + any analytes eluting from the EC system) into a chamber at atmospheric pressure. This is done in the source in the presence of a heated drying gas (usually Nj) and a strong electrostatic field. The pressure of the electrostatic field causes further dissociation of the analyte molecules and the drying gas causes the solvent to evaporate (see Figure 5.16). 

Methods Ambient ionization methods, of which there are now over 20, e.g., desorption electrospray ionization (DESI), desorption atmospheric pressure chemical ionization (DAPC), desorption atmospheric pressme photo-ionization (DAPPI), and direct analysis in real time (DART), are now joined by paper spray, a method where ESI is initiated at the pointed tip of a piece of filter paper. A drop of blood ( 15 pi) is dried on the paper, and then the paper is moistened with 25 pi of a solvent suited to both the extraction of the analytes from the blood and the ESI process (e.g., 90% methanol 10% water with either 100 ppm acetic acid or 200 ppm sodium acetate). When the paper is exposed to high voltage (3-5 kV) while held close ( 5 mm) to the entrance of the mass analyzer, a spray (similar to electrospray) is induced at the tip of the paper as capillary action carries extracted compounds through the paper (Figure 4.5). The spray is maintained for 30-90 s at a flow rate comparable to that used in nano-electrospray. 

The mass spectrometer (MS) is an analytical tool that provides information about sample composition based on the mass-to-charge ratio (m/z). In order to analyze biological samples by MS, the relevant analytes must be driven into the gas phase and ionized (charged). Two techniques are currently the most popular for the ionization of biological analytes, ESI (electrospray ionization) and MALDl (matrix-assisted laser desorp-tion/ionization). In ESI, an electric field is applied to a solution of analyte to form a spray of charged droplets. Subsequent solvent evaporation and ion release enables analysis by MS. In MALDl, the analyte is co-crystallized with a solid matrix to form a dry spot on a surface. Under vacuum, the sample is then irradiated with a laser, which desorbs the sample from the surface and ionizes it. The developers of these... 

Electrospray sample deposition (ESDEP) is a sample preparation method where matrix and analyte solutions are sprayed on the target surface under the influence of a high-voltage electric field [44,45]. ESDEP is reported to yield much better shot-to-shot and spot-to-spot reproducibility than the dried-droplet method. The improved results are ascribed to the small and evenly sized crystals that are formed, and as a consequence, improved homogeneity of the MALDI sample surface. Hanton et al. [45] analyzed PEG1450, a narrowly distributed poly(ethylene oxide) sample, using an uncommon... 

The electrospray source is shown schematically in Figure 12. A capillary is held under high voltage (3-5 kV) at atmospheric pressure to generate a spray of charged droplets. To obtain a dry aerosol, either a heated steel capillary [109] or a hot gas curtain [110] is used in conjunction with collisions in the first vacuum stage. These collisions are necessary to decluster the ionic species, but may also be used to make fragments in a process equivalent to collision-induced dissociations for MS/MS experiments. 

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