Isotope dilution-mass spectrometry reverse

Reverse isotope dilution. Reverse isotope dilution refers to the determination of the level of the isotopically labelled analogue used as a spike in an isotope dilution experiment by addition of the spike to a standard containing a known amount of the natural form of the analyte. Measurement is made as in normal isotope dilution mass spectrometry, but in this case it is the level of the labelled form that is treated as the unknown. 

Thienpont LM, Verhaeghe PG, Van Brussel KA, De Leenheer AP. Estradiol-17 beta quantified in serum by isotope dilution-gas chromatography-mass spectrometry reversed-phase C18 high-performance liquid chromatography compared with immuno-affinity chromatography for sample pretreatment. Clin Chem 1988 34 2066-9. 

Figure 4. Proposed pathways of the degradation of diflubenzuron in agricultural soils and hydrosoils. Abbreviations rid = reversed isotope-dilution ms = mass spectrometry tic = thin layer chromatography.

Seifar, R.M. et al. Quantitative analysis of metabolites in complex biological samples using ion-pair reversed-phase hquid chromatography-isotope dilution tandem mass spectrometry./. Chwmatogr. A. 2008, 1187,103-110. 

Recently, Blount et al. (2000) summarized a methodology to detect di- -butyl phthalate metabolites in urine. In humans or animals, di- -butyl phthalate is metabolized to mono- -butyl phthalate and oxidative products, which are excreted through the urine and feces. Human urine samples are processed by P-glucuronidase hydrolysis (to release the mono phthalate ester) followed by solid-phase extraction. The eluate is concentrated mono- -butyl phthalate is chromatographically resolved by reverse-phase HPLC, detected by negative ion atmospheric pressure chemical ionization (APCI) tandem mass spectrometry, and quantified by isotope dilution. 

Dombovari, )., Becker, J.S., and Dielze, H.J. (2000) Isotope ratio measurements of magnesiiun and determination of magnesium concentration by reverse isotope dilution technique on small amounts of Mg-spiked nutrient solutions with inductively coupled plasma mass spectrometry. Int. J. Mass Spectrom., 202, 231-240. 

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