Isotopic Dilution Analysis IDA

The quantitative analysis of aroma substances using conventional methods often gives incorrect values. The high vapor pressure, the poor ex-tractability especially of polar aroma substances from hydrous foods and the instability of important aroma substances, e. g., thiols, can cause unforeseeable losses in the purification of the samples and in gas chromatography. 

The results of quantitative analyses are exact (standard deviation 10%) and reproducible if the chemical structure of the internal standard is very similar to the structure of the analyte. An 

The examples given in Fig. 5.14 show that for economic reasons, mostly internal standards labelled with deuterium are synthesized for IDA. The considerably more expensive carbon isotope 13 is introduced into the odorant (examples are the internal standards No. 11 and 12 in Fig. 5.14) only if a deuterium/protium exchange can occur in the course of analysis. This exchange would falsify the result. Another advantage of this isotope is the completely negligible isotope effect compared to deuterium. 

It is easy to conduct an IDA because losses of analyte in the distillative recovery (cf. 5.2.1.1) and in purification do not influence the result since the standard suffers the same losses. These advantages of IDA are used in food chemistry for other analytes as well, e. g., pantothenic acid (cf. 6.3.5.2) or for the my cotoxin patulin (cf. 9.2.3). 

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An excellent possibility for quantifying analytical data in inorganic mass spectrometry is isotope dilution analysis (IDA) based on more precise isotope ratio measurements. IDA uses highly enriched isotope spikes of analytes of known concentration for calibration and is the method of choice if a high accuracy for element concentrations is required. The principles and applications of this method will be discussed below. 

There are certain analytical methods that can be applied to all fields of tracer use. Foremost among these is isotope dilution analysis (IDA). In this section we summarize the variants of this analytical method. 

The principle of the isotope dilution analysis (IDA) is described in Section 6.4. Due to its advantages as a definitive and accurate analytical method for the determination of element concentration via isotope ratio measurements, IDA is being increasingly applied in mass spectrometry, especially in ICP-MS and LA-ICP-MS as one of the most frequently used techniques. For example, the isotope dilution technique is employed in species analysis in biological systems, " e.g., for the determination of mercury species in tuna material,or in aquatic systems. Further applications of the isotope dilution technique are the determination of selenomethionine in human blood serum by capillary HPLC-ICP (ORC) MS ° or sulfur speciation in gas oil, diesel or heating fuel by LA-ICP-MS. Evans and co-workers have reported on the high accuracy analysis of sulfur in diesel fuel by IDA. ICP-SFMS has been employed for Si species analysis in biological or clinical samples and... 

The principle of isotope dilution analysis (IDA) is illustrated in Fig. 17.4. The sample contains an unknown number of atoms or molecules, and it may also contain an unknown number N of labelled atoms or molecules of the same kind. Known numbers N and N are added. These atoms or molecules (subscript 1) must not be identical with the atoms or molecules x, but they must exhibit the same behaviour under the given conditions. After mixing to obtain homogeneous distribution, any fraction is taken and the numbers N2 and W2 are determined in this fraction. 

Isotope dilution analysis (IDA) involves the modification of the natural isotopic composition of a target... 

Isotope dilution analysis (IDA) involves mixing an aliquant of the sample with an aliquant of an artificially enriched isotope of the element to be analyzed. The content of the latter in the original sample is derived from the results of the isotopic analysis of the mixture compared to the isotopic compositions of the sample and of the enriched isotope. The term spiking is often used to refer to the mixing step. The aliquant of enriched isotope added to the sample is also commonly called a spike. IDA is used in particular for the determination of uranium, plutonium, or thorium in solutions of irradiated nuclear fuels. It has also been used for an independent measurement of the total volume or mass of solution in accountability tanks of chemical processing plants. 

Dahmen, L, Pfluger, M., Martin, M., Rottmann, L., Weichbrodt, G. (1997) Trace element determination of high-purity chemicals for the processing of semiconductors with high-resolution ICP-mass spectrometry using stable isotope dilution analysis (IDA). Fresenius Journal of Analytical Chemistry, 359,410-413. 

Radionuclides are used in many subdivisions of analytical chemistry (see Table 1). Of major importance are radiotracers in methodological and pathway studies, isotope dilution analysis (IDA), radioimmunoassay, and nuclear activation analysis (AA) (- Activation Analysis) [66]. They are all especially suited to analyze the extremely small amounts of substances encountered in ultra-trace analysis or in trace analysis of microsamples. 

The principle of isotope dilution analysis (IDA) [31], [47], [90]. [97], [98] involves measurement of the change in isotopic ratio when portions of a radiolabeled and nonlabeled form of the same chemical species are mixed. To perform a radioisotope IDA. an aliquot of a radioactive spike substance of known specific activity o,=A,/ni/ is... 

Guth, H. (1996) Use of the Moving Capillary Switching System (MCSS) in combination with stable Isotope Dilution Analysis (IDA) for the quantification of a trace component in wine. Poster at the 18th International Symposium on Capillary Chromatography, Riva del Garda, Italy, May 20-24, 1996. 

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