Ion-spray

Another big advance in the appHcation of ms in biotechnology was the development of atmospheric pressure ionization (API) techniques. There are three variants of API sources, a heated nebulizer plus a corona discharge for ionization (APCl) (51), electrospray (ESI) (52), and ion spray (53). In the APCl interface, the Ic eluent is converted into droplets by pneumatic nebulization, and then a sheath gas sweeps the droplets through a heated tube that vaporizes the solvent and analyte. The corona discharge ionizes solvent molecules, which protonate the analyte. Ions transfer into the mass spectrometer through a transfer line which is cryopumped, to keep a reasonable source pressure. 

D. Puig, L. Silgoner, M. Grasserbauer and D. Barcelo, Part-per-trillion level determination of priority methyl-, nirto-, and clilor ophenols in river water samples by automated online liquid/solid exrtaction followed by liquid chr omatography/mass spectr ometry using atmospheric pressure chemical ionization and ion spray interfaces . Anal. Chem. 69 2756-2761 (1997). 

Saito et al. achieved the first direct confirmation of double alkylation of purine bases by azinomycin B [140]. They incubated azinomycin B with the self-comple-mentary DNA duplex d(TAGCTA)2 and monitored the reaction by HPLC and ion spray MS. They observed initial formation of a monoadduct that was then converted into a crosslinked bisadduct. The crosslink position was identified as between the guanine of one strand and the 5 -adenine on the other strand by thermo-lytic depurination. Further decomposition prevented structural analysis of the azi-... 

The ion spray liquid chromatography/mass spectrometry (LC-MS) interface coupled via a postsuppressor split with an ion chromatography (IC) has been used in the analysis of alcohol sulfates. The IC-MS readily produces the molecular weight while the tandem mass spectrometric detection IC-MS-MS provides structural information [305]. 

Sagesser, M. and Deinzer, M., HPLC-ion spray-tandem mass spectrometry of flavonol glycosides in hops, J. Am. Soc. Brew. Chem., 54, 129, 1996. 

E. M. Thurman and C. Batian, Determination of atrazine and atrazine mercapture in drinking water samples and in urine using immunoaffinity SPE with positive ion spray HPLC/MS , Presented at the 15th Symposium on Liquid Chromatography/Mass Spectrometry, Montreux, Switzerland, November 9-10, 1998. 

Suzuki-Sawada, J., Umeda, Y., Kondo, A., and Kato, I., Analysis of oligosaccharides by on-line high-performance liquid chromatography and ion-spray spectrometry, Anal. Biochem., 207, 203, 1992. 

Fast atom bombardment (FAB) Plasma desorption (PD) Liquid secondary-ion mass spectrometry (LSIMS) Thermospray (TSP)/plasmaspray (PSP) Electrohydrodynamic ionisation (EHI) Multiphoton ionisation (MPI) Atmospheric pressure chemical ionisation (APCI) Electrospray ionisation (ESI) Ion spray (ISP) Matrix-assisted laser desorption/ionisation (MALDI) Atmospheric pressure photoionisation (APPI) Triple quadrupole (QQQ) Four sector (EBEB) Hybrid (EBQQ) Hybrid (EB-ToF, Q-ToF) Tandem ToF-ToF Photomultiplier... 

The ionspray (ISP, or pneumatically assisted electrospray) LC-MS interface offers all the benefits of electrospray ionisation with the additional advantages of accommodating a wide liquid flow range (up to 1 rnl.rnin ) and improved ion current stability [536]. In most LC-MS applications, one aims at introducing the highest possible flow-rate to the interface. While early ESI interfaces show best performance at 5-l() iLrnin, ion-spray interfaces are optimised for flow-rates between 50 and 200 xLmin 1. A gradient capillary HPLC system (320 xm i.d., 3-5 xLmin 1) is ideally suited for direct coupling to an electrospray mass spectrometer [537]. In sample-limited cases, nano-ISP interfaces are applied which can efficiently be operated at sub-p,Lmin 1 flow-rates [538,539]. These flow-rates are directly compatible with micro- and capillary HPLC systems, and with other separation techniques (CE, CEC). 

Lee, E.D., Muck, W., Henion, J.D., Covey, T.R (1988). On-line capillary zone electrophoresis-ion spray tandem mass spectrometry for the determination of dynorphin. J. Chromatogr. 458, 313-321. 

For the last several years, mass spectrometry with atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) have determined the trends in the analysis of dyes. Since 1987, various variants of ESI have been used in which droplet formation was assisted by compressed air,[1,2] temperature (e.g. Turbo Ion Spray ) or ultrasound, and they were able to handle flow rates up to 1 2 ml min This made a combination of analytical RPLC and ESI easily and widely used. The reason why it often was (and is) used instead of a traditional UV-Vis detector is the better sensitivity and selectivity of MS in comparison with spectrophotometric detection. Apart from these advantages, MS offers easily interpretable structural information. However, various... 

A.P. Bruins, T.R. Covey and J.D. Henion, Ion spray interface for combined liquid chromato graphy/atmospheric pressure ionization mass spectrometry, Anal. Chem., 59,2642 2646 (1987). 

G. Hopfgartner, T. Wachs, K. Bean and J. Henion, High flow ion spray liquid chromatography/ mass spectrometry, Anal. Chem., 65, 439 446 (1993). 

Rauha JP, Vuorela H and Kostiainen R. 2001. Effect of eluent on the ionization efficiency of flavonoids by ion spray, atmospheric pressure photoionization mass spectrometry. J Mass Spectrom 36 1269-1280. 

The differences in ionisation efficiencies, however, not only result from the use of FIA or LC but, as mentioned before, depend also on the application of the APCI or ESI interface for ionisation. Therefore the application of both API methods, APCI and ESI, is the only way to overcome discrimination problems because of interface type selection. Even the use of the ion spray technique instead of conventional ESI may influence the ionisation efficiency considerably. 

LC separation applying ion chromatography in combination with ion spray mass spectrometric detection was applied for the examination of a synthetic mixture of alkyl sulfonates (CnH2n+i-SO3 re = 8) and AS with different alkyl chain lengths in the selected ion monitoring (SIM) ESI-MS(—) mode [53], Selected ion current profiles provided the separation of the compounds. The ionic matrix constituents of the eluent were removed by a suppressor module prior to MS detection to improve the signal to noise (S/N) ratio. 

As a by-product of AES analysis, ASs were separated by LC-EP-Ci8 [52], combined with ion spray (ESI(—)) ionisation and then this method was used for monitoring individual species of the ASs (CraH2n+1-0-SOs) and AESs by ESI-LC-MS. In addition, RP-C2 material had been applied for SPE of the pollutants prior to MS analysis. 

One of the first results dealing with MS-MS investigations of quats was published by Conboy et al. [36]. Industrially important quats were separated by IC and determined by ion spray MS in the ESI(+) mode. Full scan IC-MS-MS spectra were presented from tetraalkyl ammonium compounds examined. They varied in the alkyl groups, starting at C3H7 and ending at C6H13. 

Puig et al. [450] determined ng/1 levels of priority methyl-, nitro-, and chloro-phenols in river water samples by an automated on-line SPE technique, followed by liquid chromatography-mass spectrometry (LC-MS) using atmospheric pressure chemical ionization (APCI) and ion spray interfaces. 

The mass spectrometer is a very sensitive and selective instrument. However, the introduction of the eluent into the vacuum chamber and the resulting significant pressure drop reduces the sensitivity. The gas exhaust power of a normal vacuum pump is some 10 ml min-1 so high capacity or turbo vacuum pumps are usually needed. The gas-phase volume corresponding to 1 ml of liquid is 176 ml for -hexane, 384 ml for ethanol, 429 ml for acetonitrile, 554 ml for methanol, and 1245 ml for water under standard conditions (0°C, 1 atmosphere). The elimination of the mobile phase solvent is therefore important, otherwise the expanding eluent will destroy the vacuum in the detector. Several methods to accomplish this have been developed. The commercialized interfaces are thermo-spray, moving-belt, electrospray ionization, ion-spray, and atmospheric pressure ionization. The influence of the eluent is very complex, and the modification of eluent components and the selection of an interface are therefore important. Micro-liquid chromatography is suitable for this detector, due to its very small flow rate (usually only 10 p min - ). 

Note Pneumatically assisted electrospray is also termed ion spray (ISP). However, the term ISP is not recommended instead of pneumatically assisted ESI because ISP i) represents a mere modification of the ESI setup and ii) is a company-specific term. [63]... 

Anacleto, J.F. Pleasance, S. Boyd, R.K. Calibration of Ion Spray Mass Spectra Using Cluster Ions. Org. Mass Spectrom. 1992,27, 660-666. 

Bruins, A.P. Covey, T.R. Henion, J.D. Ion Spray Interface for Combined Liquid Chromatography/Atmospheric Pressure lonization-MS. Anal. Chem. 1987, 59, 2642-2646. 

Kronstrand R, Nystrom I, Strandberg J, Druid H. 2004. Screening for drugs of abuse in hair with ion spray LC-MS-MS. Forensic Sci Int 145 183. 

Huggins, T. G., and Henion, J. D. (1993). Capillary electrophoresis/mass spectrometry determination of inorganic ions using and ion spray-sheath flow interface. Electrophoresis 14, 531 — 539. 

Mordehai, A., Lim, H. K., and Henion, J. D. (1995). Ion-spray liquid-chromatography mass-spectrometry and capillary electrophoresis mass-spectrometry on a modified benchtop ion-trap mass-spectrometer. In Practical Aspects of Ion-Trap Mass Spectrometry Chemical, Environmental and Biomedical Applications (R. E. March, and J. F. J. Todd, Eds), Vol. 3, pp. 215—237, CRC Press, Boca Raton, FL. 

Lee, E. D., Mueck, W., Henion, J. D., and Covey, T. R. (1989). Liquid junction coupling for capillary zone electrophoresis/ion spray mass spectrometry. Biomed. Environ. Mass Spectrom. 18, 844—850. 

Garcia, R, and Henion, J. (1992). Fast capillary electrophoresis-ion spray mass spectrometric determination of sulfonylureas. J. Chromatogr. 606, 237—247. 

Sheppard, R. L., and Henion, J. (1997). Quantitative capillary electrophoresis ion spray tandem mass spectrometry determination of EDTA in human plasma and urine. Anal. Chem. 69, 2901-2907. 

Von Brocke, A., Wistuba, D., Gfrorer, P., Stahl, M., Schurig, V, and Bayer, E. (2002). On-line coupling of packed capillary electrochromatography with coordination ion spray-mass spectrometry for the separation of enantiomers. Electrophoresis 23, 2963 — 2972. 

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