Electrospray drying

Gomez, A. Bingham, L.de Juan Tang, K. Production of protein nanoparticles by electrospray drying. J. Aerosol Sci. 1998, 29, 561-574. 

Faezeh, B.-T., 2005, Preparation of polyetherimide nanoparticles by electrospray drying, and their use in the preparation of nano-size carbon molecular sieve (CMS) adsorbents and membranes. The 2005 AIChE Annual, Cincinnati, OH, http // aiche.confex.eom/aiche/2005/techprogram/P32246.HTM. 

However, interpretation of, or even obtaining, the mass spectrum of a peptide can be difficult, and many techniques have been introduced to overcome such difficulties. These techniques include modifying the side chains in the peptide and protecting the N- and C-terminals by special groups. Despite many advances made by these approaches, it is not always easy to read the sequence from the mass spectrum because some amide bond cleavages are less easy than others and give little information. To overcome this problem, tandem mass spectrometry has been applied to this dry approach to peptide sequencing with considerable success. Further, electrospray ionization has been used to determine the molecular masses of proteins and peptides with unprecedented accuracy. 

Matrix-assisted laser desorption mass spectrometry (MALDI-MS) is, after electrospray ionization (ESI), the second most commonly used method for ionization of biomolecules in mass spectrometry. Samples are mixed with a UV-absorbing matrix substance and are air-dried on a metal target. Ionization and desorption of intact molecular ions are performed using a UV laser pulse. 

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.

HPLC-mass spectrometry (MS). MS conditions ionization mode, atmospheric pressure ionization-electrospray (API-ES) polarity, positive Vcap, 4000 V nebulizer pressure, 35 psig drying gas, 10 L min gas temperature, 350 °C fragmentor, 70 V scan range, 120-600 atm. 

Reverse-phase columns with a gradient elution in combination with UV-Vis spectrophotometers using photodiode-array (PDA) (Fig. 1.6) and spectrofiuorimeters are common devices employed in this technique. In a lesser extent, MS, tandem mass spectrometry (MS-MS), and nano liquid chromatography-electrospray ionization-quadrupole time-of-flight tandem mass spectrometry (nanoLC-nanoESI-Q-qTOF-MS-MS) has been used as detection system. This instrumentation has been mainly used in the analysis of dyes and proteinaceous media, and in some extent, in the analysis of drying oils and terpenoid varnishes [47,48],... 

Lai CC, Tsai CH, Tsai FJ, Wu JY, Lin WD, Lee CC (2002) Rapid screening assay of congenital adrenal hyperplasia by measuring 17 alpha-hydroxyprogesterone with high-performance liquid chromatography/electrospray ionization tandem mass spectrometry from dried blood spots. J Clin Lab Anal 16 20-25... 

Carducci C, Santagata S, Leuzzi V, Carducci C, Artiola C, Giovanniello T, Battini R, Antonozzi I (2006) Quantitative determination of guanidinoacetate and creatine in dried blood spot by flow injection analysis-electrospray tandem mass spectrometry. Clin Chim Acta 364 180-187... 

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