Ionspray ionization

In recent decades the hyphenated technique, HPLC-MS, also become the method of preference in HPLC practice. Various techniques have been developed and applied for MS detection such as thermo-spray interface, atmospheric ionization (API), electrospray or ionspray ionization (ESI or ISI), and particle beam ionization. 

Mano, N., Oda, Y. and Yamada, K. (1997) Simultaneous quantitative determination method for sphingolipid metabolites by liquid chromatography/ionspray ionization tandem mass spectrometry. Anal. Biochem., 244 (2), 291-300. 

One of the most powerful techniques used in Upid analysis today is HPLC coupled with mass spectrometry (HPLC/MS). Several mass spectrometric ionization techniques, such as fast atom bombardment (FAB) [23], electrospray ionization (ESI) [29,30], ionspray ionization (ISI) [31], and atmospheric pressure chemical ionization (APCI) [22,30,32] have been used. By using HPLC/MS, one can get information on the molecular structure of the intact lipids, which helps differentiate molecular species within different lipid classes. By using tandem mass spectrometry (MS/MS), identification of molecular species of different sphingolipids can be achieved in an easier and more sensitive way. There are many other advantages of using MS, such as small sample size, minimal sample preparation, and lack of need for derivatization, speeds, and sensitivity. In the literature, sphingolipids of both animal and plant origin were analyzed by MS. 

ESI, electrospray ioni2ation in positive (+) or negative (-) modes IS, ionspray ionization. Analysis of Lupinus angustifolius only. 

Horimoto, S. Mayumi, T. Tagawa, K. Yamakita, H. Yoshikawa, M. Determination of taltireUn, a new stable thyrotropin-releasing hormone analogue, in human plasma by high-performance Uquid chromatography turbo-ionspray ionization tandem mass spectrometry, J.Pharm.BiomedJinal., 2002, 50, 1361 1369. 

A number of interfaces such as thermospray (TSP), ionspray (IS), atmospheric chemical ionization (APCI) and electrospray (ES) can tolerate much higher flow rates without requiring that the flow be split at the end of the LC column. Ions that are produced in atmospheric pressure ionization sources are moved directly into the mass spectrometer through small apertures. 

Ionization methods such as electrospray, ionspray, and atmospheric pressure chemical ionization, in which the analyte is sprayed at atmospheric pressure into an interface to the vacuum of the MS ion source, constitute the category of the atmospheric pressure ionization. 

NSTD, nitrogen-selective thermionic detector ISP, ionspray TSP, thermospray ESP, electrospray PICI, positive-ion chemical ionization NICI, negative-ion chemical ionization PPINICI, pulsed positive-ion-negative ion-chemical ionization PDA, photodiode array SDS, sodium dodecylsulfate CPase, carboxypeptidase. 

Coupling of liquid chromatography with mass spectrometry allows unequivocal online spectrometric identification of all nitrofurans at the very low residue concentrations required by regulatory agencies for confirmatory analysis in animal-derived foods. Typical examples of mass spectrometry applications in confirming nitrofuran residues in edible animal products employ thermospray (174, 176), ionspray (166), or atmospheric pressure chemical ionization (157) interfaces. 

Reaction was monitored by analytical HPLC (4 pL aliquots). Peaks were collected based on UV absorbance and examined by ionspray MS)106 Although salts generally interfere with the evaporative ionization process, the dil NHtOAc buffer used was compatible with direct IS-MS of synthetic peptides. After 6.5 h at 23 °C, the mixture was stored at 4°C. Product (170 pL of mixture) was purified by RP-HPLC (38-54% buffer B over 30 min at 3 mL min ) and lyophilized giving pure product yield 0.26 mg (20.5%). The mass was determined by IS-MS calcd, 6649.9 found, 6647.1 (average isotope composition). 

A. High-performance liquid chromatography-mass spectrometry Weidolf and Covey [121] described the application of the ionspray interface for liquid chromatography and atmospheric-pressure ionization mass spectrometry to samples obtained in a study on the metabolism of... 

The phosphonic acids are strong acids (pKA 2) and under typical LC conditions exist mostly in the deprotonated form. They are therefore well suited to both negative and positive ionization. Kosti-ainen et al. (24) reported negative-ion ESI (ionspray) spectra for alkyl methylphosphonic acids (alkyl MPAs), 0-ethyl methylphosphonothioic acid, and... 

The ionspray Merfaee, first described by Bruins et al. [14] in 1987, was introdueed in order to eombine the principles of ion evaporation (Ch. 3.2.3) and ESI. However, the prime ionization mechanisms of both approaches appeared to be similar. The main advantage of ionspray or pneumatically-assisted ESI over the eonventional ESI is the higher flow-rates (up to 200 pl/min instead of 10 pl/min) that can be aeeommodated. 

Among the currently available interfaces for drug residue analysis, the most powerful and promising appear to be the particle-beam (PB) interface, the thermospray (TSP) interface that works well with substances of medium polarity, and the atmospheric pressure ionization (API) interfaces that have opened up important application areas of LC to LC-MS for ionizable compounds. Among the API interfaces, electrospray (ESP) and ionspray (ISP) appear to be the most versatile as they are suitable for substances ranging from polar to ionic and from low to high molecular mass. Ionspray, in particular, is compatible with the flow rates used with conventional LC columns. In addition, both ESP and ISP appear to be valuable in terms of analyte detectability. 

Mass spectrometry (MS) has become one of the most important analytical tools employed in the analysis of pharmaceuticals. This can most likely be attributed to the availability of new instrumentation and ionization techniques that can be used to help solve difficult bioanalytical problems associated with this field (1-8). Perhaps the best illustration of this occurrence is the development of electrospray (ESI) and related atmospheric-pressure ionization (API) techniques, ion-spray (nebulizer-assisted API), turbo ionspray (thermally assisted API), and atmospheric pressure chemical ionization (APCI nebulization coupled with corona discharge), for use in drug disposition studies. The terms ESI and ionspray tend to be used interchangeably in the literature. For the purpose of this review, the term API will be used to describe both ESI and ionspray. In recent years there has been an unprecedented explosion in the use of instrumentation dedicated to API/MS (4,6,8-14). API-based ionization techniques have now become the method of choice for the analysis of pharmaceuticals and their metabolites. This has made thermospray (TSP), the predominant LC/MS technique during the 1980s, obsolete (15). Numerous reports describing the utility of API/MS for pharmaceutical analysis have appeared in the literature over the last decade (7). The... 

Liquid introduction in atmospheric pressure chemical ionization resembles ionspray except that a heated capillary is used in place of the charged capillary. Figure 9.7. The combination of heat and gas flow desolvates the nebulized droplets producing fine particles of solvent and analyte molecules. The solvent molecules are then ionized by a corona discharge and the solvent ions formed ionize the analyte molecules by atmospheric pressure chemical ionization. 

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