Double isotope dilution analysis

A major difficulty with double isotope dilution analysis is that, because of the double dilution, the specific activities involved become low and therefore more uncertain. 

The weak point of the above inverse isotope dilution analysis is that the specific activity So of the compound to be determined in the original sample solution must be known. This can be avoided by double isotope dilution analysis. In this type of analysis, two portions of exactly the same amount are taken from the sample solution. The mass of the radioactive compound in each portion is taken to be X. To the portions are added different masses Wi and W2 of the inactive compound. Taking the specific activities of the compound in the portions after this to be Si and S2,... 

Boelrijk, N.A.I.M. (1968) A general formula for double isotope dilution analysis. Chem. Geol, 3, 323-325. 

QUANTITATIVE TECHNIQUES Isotope dilution analysis Direct dilution analysis Reverse isotope dilution analysis Derivative analysis Double isotope dilution analysis Saturation analysis Radioenzymatic assays... 

Isotope ratio measurements were employed for the quantification of analytical data using the isotope dilution strategy. For example, isotope dilution analysis was developed by Sanz-Medel s group for the determination of selenomethionine in Se enriched yeast material by HPLC-ICP-MS using a Se-enriched selenomethionine spike obtained by growing yeast on a Se rich culture medium. For Cr(III)/Cr(VI) determination in yeast, Caruso et al employed the double spike species specific isotope dilution technique measured by HPLC-ICP-MS. The isotope pattern deconvolution approach applied in this work delivers a more intuitive and elegant solution to an otherwise complex data analysis without the need for iterative calculations as widely practised in double spike isotope dilution. The results are in exact agreement with the conventional isotope dilution calculations. ... 

As mentioned in the Section 1, physico-chemical methodology for quantitative analysis of plant hormone focuses primarily on GC-SIM, although HPLC with selective fluorescence detection continues to be used for lAA analysis in some laboratories. Procedures, such as the 2-methylindolo-a-pyrone assay for lAA analysis [82], are now rarely utilised. With the exception of ethylene quantification [2] there is little use of non-MS-based GC detection techniques, despite the fact that selective analysis at the picogram level is achieved for ABA with an electron capture detector [83], and lAA and cytokinins with a nitrogen phosphorus detector [84,85]. The reason for the demise of these GC procedures is that the detectors are destructive and this precludes the reliable recovery of labelled internal standards for radioassay and isotopic dilution analysis. The usual compromise was to take two aliquots of the purified samples, one for GC analysis and the other for the determination of radioactivity. The accuracy of this approach is dependent upon the questionable assumption that the radioactivity in the purified sample is associated exclusively with the compound under study. In an attempt to circumvent this problem, a double standard isotope dilution procedure was devised for the quantitative analysis of lAA in which one internal standard was used to correct for losses during sample preparation and a second for GC quantification [86]. This procedure was used in several... 

Muniz et al. quantitatively analyzed the metal containing proteins in human serum by anion-exchange chromatography coupled to post-column isotope dilution analysis with double focusing ICP-MS. Parallel analysis of human serum from healthy volunteers and patients on hemodialysis was also undertaken. They found different amounts of iron-containing proteins between healthy and renal disease individuals and indicated that Fe bound to albumin decreased in patients with renal disease. ... 

Sariego MuThiz, C., Marchante Gayon,J. M., Garcia Alonso, J. I., and Sanz-Medel,A. (1999). Accurate determination of iron, copper and zinc in human serum by isotope dilution analysis using double focusing ICF-MS.J.Anal.At. Spectrom. 14(9), 1505. 

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