Mass spectrometry quantitative comparison

Chang, Y.-C., Li, C.-M., Li, L.-A., Jong, S.-B., Liao, P.C. and Chang, L.W. (2003). Quantitative measurement of male steroid hormones using automated on-line solid phase extraction liquid chromatography-tandem mass spectrometry and comparison with radioimmunoassay. Analyst, 128, 363-368. 

Quantitation using mass spectrometry is no different to quantitation using other techniques and, as discussed above in Section 2.5, involves the comparison of the intensity of a signal generated by an analyte in a sample to be determined with that obtained from standards containing known amounts/concentrations of that analyte. 

Figure 5.67 Reconstructed ion chromatograms for Idoxifene and internal standard (ds-Idoxifene using LC-ToF-MS for (a) double-blank human plasma extract, (b) extract of blank human plasma containing internal standard (IS), and (c) control-blank human plasma spiked with Idoxifene at 5 gml , the LOQ of the method. Reprinted from 7. Chromatogr., B, 757, Comparison between liquid chromatography-time-of-flight mass spectrometry and selected-reaction monitoring liquid chromatography-mass spectrometry for quantitative determination of Idoxifene in human plasma , Zhang, H. and Henion, J., 151-159, Copyright (2001), with permission from Elsevier Science.

Residues of isoxaflutole, RPA 202248 and RPA 203328 are extracted from surface water or groundwater on to an RP-102 resin solid-phase extraction (SPE) cartridge, then eluted with an acetonitrile-methanol solvent mixture. Residues are determined by liquid chromatography/tandem mass spectrometry (LC/MS/MS) on a Cg column. Quantitation of results is based on a comparison of the ratio of analyte response to isotopically labeled internal standard response versus analyte response to internal standard response for calibration standards. 

Table 8.60 shows the main features of GD-MS. Whereas d.c.-GD-MS is commercial, r.f.-GD-MS lacks commercial instruments, which limits spreading. Glow discharge is much more reliable than spark-source mass spectrometry. GD-MS is particularly valuable for studies of alloys and semiconductors [371], Detection limits at the ppb level have been reported for GD-MS [372], as compared to typical values of 10 ppm for GD-AES. The quantitative performance of GD-MS is uncertain. It appears that 5 % quantitative results are possible, assuming suitable standards are available for direct comparison of ion currents [373], Sources of error that may contribute to quantitative uncertainty include sample inhomogeneity, spectral interferences, matrix differences and changes in discharge conditions. 

Moritz, T. Olsen, J.E. Comparison Between High-Resolution Selected Ion Monitoring, Selected Reaction Monitoring, and Four-Sector Tandem Mass Spectrometry in Quantitative Analysis of Gib-berellins in Milligram Amounts of Plant Tissue. Anal. Chem. 1995, 67, 1711-1716. 

Zhang, H., and Henion, J. (2001). Comparison between liquid chromatography-time-of-flight mass spectrometry and selected reaction monitoring liquid chromatography-mass spectrometry for quantitative determination of idoxifene in human plasma. J. Chromatogr. B Biomed. Sci. Appl. 757 151-159. 

Gobey, J. S., Janiszewski, J., Credo, G. M., and Bouvier, E. S. P. (2004). A comparison of desorption ionization techniques for small molecule quantitation. In Proceedings of The 52nd ASMS Conference on Mass Spectrometry and Allied Topics, Nashville, TN. 

Quantitation Once protein expression profiling activities characterize qualitative features, the attention turns to delineating protein interactions and mechanistic pathways responsible for disease. These studies also require rapid sequence determination/confirmation combined with accurate and sensitive quantitative analysis. The quantitation approaches would allow for direct comparison of protein amounts (absolute or relative) from a variety of cellular states. Because of the reasons stated previously, quantitative applications are likely to be less dependent on 2-DGE and rely primarily on formats that involve specific purification and/or chromatographic separation with mass spectrometry. 

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