Sonic spray

Solutions of solids may need to be converted into aerosols by pneumatic or sonic-spraying techniques. After solvent has evaporated from the aerosol droplets, the residual particulate solid matter can be ionized by a plasma torch. 

A detailed description of sources used in atmospheric pressure ionization by electrospray or chemical ionization has been compiled.2 Atmospheric pressure has been used in a wide array of applications with electron impact, chemical ionization, pressure spray ionization (ionization when the electrode is below the threshold for corona discharge), electrospray ionization, and sonic spray ionization.3 Interferences potentially include overlap of ions of about the same mass-charge ratio, mobile-phase components, formation of adducts such as alkali metal ions, and suppression of ionization by substances more easily ionized than the analyte.4 A number of applications of mass spectroscopy are given in subsequent chapters. However, this section will serve as a brief synopsis, focusing on key techniques. 

A home-built spray ion source, operable in both the sonic-spray ionization (SSI) and electrospray ionization (ESI) modes, was used instead of the standard ESI source of the Einnigan LCQ instrument. (Erom Takats et al., 2003b)... 

Figure 1. Schematic cross section of sonic spray ion source. Liquid sample is pneumatically sprayed by the coaxial gas flow. The cross section of the gas flow in this source is restricted to 0.017 mmh...

Takats, Z. Nanita, S. C. Cooks, R. G. Schlosser, G. Vekey, K. Amino Acid Clusters Formed by Sonic Spray Ionization. Anal Chem. 2003a, 75, 1514-1523. 

The real breakthrough in LC/MS development was achieved with the broad introduction in the 1990s of atmospheric pressure ionization (API) techniques, such as electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI), which enable the analysis of a wide variety of molecular species. The spectrum of available API techniques has been amended meanwhile by the introduction of sonic spray ionization (SSI) and atmospheric pressure photoionization (APPI). 

Dams et al. [19] determined seven different opium alkaloids and derivatives in seized heroin using fast LC-MS analysis. Analytes were separated in 5 min on a monolithic silica column with a gradient elution system and an optimized flow of 5 mL/min. Detection was carried out using a sonic spray ion source [20] a modified ESI source were ionization is achieved using a nebulizer gas at sonic speed instead of applying an electrical field. 

Kanazawa et al. [124] determined omeprazole and its metabolites in human plasma by liquid chromatography-three-dimensional quadrupole mass spectrometry with a sonic spray ionization interface. The analytical column was YMC-Pack Pro Cig (5 cm x 2 mm) using acetonitrile-50 mM ammonium acetate (pH 7.25) (1 4) at a flow-rate of 0.2 ml/min. The drift voltage was 30 V. The sampling aperture was heated at 110 °C and shield temperature was 230 °C. In the mass spectrum, the molecular ions of omeprazole, hydroxyomeprazole, and omeprazole sulfone were clearly observed as base peaks. The method is sufficiently sensitive and accurate for pharmacokinetic studies of omeprazole. 

Gardner, J. S., Harrison, R. G., Lamb, J. D., Dearden, D. V., Sonic spray ionization mass spectrometry a powerful tool used to characterize fragile metal-assembled cages. New]. Chem. 2006, 30, 1276-1281. 

LLE liquid-liquid extraction, SPE solid phase extraction, LPME liquid-phase microextraction, ESI electrospray ionization, APCI atmospheric pressure chemical ionization, SSI sonic spray ionization, Q quadrupole, QqQ triple quadrupole, TOF time-of-flight, IT ion trap, IS internal standard, CV coefficient of variation, MRE mean relative error, LOD limit of detection, LLOQ lower limit of quantification... 

Currently, API based LC-MS interfaees, i.e., ESI and APCI, are the most widely applied approaches, while other interfaces like TSP and Cf-FAB can be considered obsolete. Despite the successes of these commercially available interfaces, research towards newer and/or advanced interface strategies continues. These research efforts comprise among others the implementation of on-line LC-MS using matrix-assisted laser desorption/ionization (Ch. 5.9), the sonic spray (Ch. 5.7.1), and the laser spray (Ch. 5.7.2) interface. 

A. Hirabayashi, M. Sakairi, H. Koizumi, Sonic spray ionization method for API-MS,... 

Paramethoxyamphetamine is an ilhcit designer drag that recently caused a number of lethal intoxications. A method of its analysis together with 3,4-MDMA and related snbstances was reported by Mortier et al. [71], based on LLE of whole blood, nrine or post-mortem tissnes, narrow-bore LC coupled to an ion-trap MS via a sonic-spray interface (Ch. 5.7.1). The early eluting contamination was directed to waste. The method was validated for all three matrices precision was better than 17.5% and the accnracy better than 16.2%. Linearity ranging from 10 to 1000 ng/ml in blood and nrine and 20 to 2000 ng/g in tissue were obtained. 

K.A. Mortier, R. Dams, W.E. Lambert, E.A. De Letter, S. Van Calenbergh, A.P. De Leenheer, Determination of paramethoxyamphetamine and other amphetamine-related designer drugs by LC-sonic spray ionization MS, Rapid Commun. Mass Spectrom., 16 (2002) 865. 

Hirabayashi A, de la Mora JF. Charged droplet formation in sonic spray Int J Mass Spectrometr Ion Processes 1998 175 277-82. 

Hirabayashi A, Sakairi M, Koizumi H. Sonic spray mass spectrometry Anal Chem 1995 67 2878-82. 

Several ionization methods have been applied for CE-MS couphng. Matrix-assisted laser desorption ionization (MALDI), continuous flow fast atom bombardment (FAB), laser vaporization ionization with UV laser, sonic spray ionization and electrospray ionization (ESI) have all been used for coupling CE to MS. However, ESI is now undoubtedly the most widely used ionization technique, employing numerous analyzers including quadrupoles, magnetic sector, Fourier transform ion cyclotron resonance, time-offlight and trapping devices. However, quad-rupole detectors have predominantly been applied in CE-MS [6-8]. 

Acteoside (verbascoside 1) was isolated as an amorphous powder. The sonic spray ion mass (SSI-MS) showed the negative ion at m/z 623 461 (M-163) ... 

Hirabayashi, A. Sakairi, M. Koizumi, H. Sonic spray mass spectrometry. Anal. Chem. 1995, 67, 2878-2882. 

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