Signal mass spectrometry

Table 5.15 Relative signal responses from various injection volumes for the LC-MS-MS analysis of a wheat forage matrix sample. Reprinted from J. Chromatogr., A, 907, Choi, B. K., Hercules, D. M. and Gusev, A. L, Effect of liquid chromatography separation of complex matrices on liquid chromatography-tandem mass spectrometry signal suppression , 337-342, Copyright (2001), with permission from Elsevier Science...

Figure 37b presents the variation of the mass spectrometry signal at m/z = 61 with the electrode potential recorded during ethanol oxidation in a 0.5 M H2SO4 + 0.5 M ethanol electrolyte. 

Calibration of the instrument is the first essential step of a quantitative procedure. Like any other analytical instrument, the response of a mass spectrometer is not absolute and might deviate with time. In addition, the sample matrix has a variable influence on the mass spectrometry response. Calibration involves determination of the correlation between a known concentration of the analyte and the resulting mass spectrometry signal. In ideal situations, the sample and the analyte standards are both analyzed under identical experimental conditions. Depending on the levels of accuracy and precision that are required, the calibration might be performed by one of the methods described below. 

In this chapter, quantitative applications of mass spectrometry were discussed. In this respect, mass spectrometry is distinctly superior over most other analytical techniques. Mass spectrometry-based methods are more specific and highly sensitive. In combination with high-resolution separation devices, the task of quantitation of real-world samples becomes much easier. A mass spectrometry signal is acquired in the SIM or SRM mode. In SIM, the ion current due to one or more compound-related ions is recorded, whereas in SRM, precursor-product... 

For precise and accurate quantification, it is essential to obtain a calibration curve to accurately define the relation between a known concentration of the analyte and the mass spectrometry signal. Calibration is performed with the external calibration, standard addition, or internal standard method. The last method is more accurate because an internal standard can account for deviation in the mass spectrometry response and the sample losses that might occur in various samplehandling and chromatographic steps. An internal standard is any compound that has chemical and physical properties similar to those of the analyte or homologous to the analyte or a stable isotope-labeled analog of the analyte. The last type of standard provides more accurate results because its chemical and physical properties are virtually identical to those of the analyte. 

Mouhib,T., Delcorte, A., Poleunis, C., Bertrand, P. (2010) Organic secondary ion mass spectrometry signal... 

In mass spectrometry signals are obtained for each isotope present. With the low mass resolution of quadrupole mass spectrometers ( 1 dalton), this leads to a number of isobaric interferences, which can be corrected for with appropriate software. This type of interference depends only slightly on the working conditions, which is not the case for spectral interferences resulting from doubly charged ions, background species or cluster ions. The background species at low masses [512] cause considerable spectral interferences e.g. for Si+ (with (with... 

Hobbs, S. E., and Olesik, J. W. (1992). Inductively coupled plasma mass spectrometry signal fluctuations due to individual aerosol droplets and vaporizing particles. Anal. Chem. 64(3), 274-282. 

Jeong, S. H., Borisov, O.V.,Yoo,J. H., Mao, X. L., and Russo, R. E. (1999). Effects of particle size distribution on inductively coupled plasma mass spectrometry signal intensity during laser ablation of glass samples. Anal. Chem. 71(22), 5123. 

Balsanek, W. J., Venable, J. D., and Holcombe, J. A. (2003) Generation of a square wave inductively coupled plasma scanning mass spectrometry signal using electrothermal vaporization sample introduction. J. Anal At. Spectrom., 18,59-64. 

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