Stable-isotope dilution assay, use

Freisleben, A., Sehieberle, P, Ryehlik, M. (2003 May). Specific and sensitive quantification of folate vitamers in foods by stable isotope dilution assays using high-performance liquid chromatography-tandem mass speetrometry. Anal. Bioanal. Chem., 376 2), 149-156. 

M. Lindenmeier, P. Schieberle, M. Rychlik, Quantification of OTA in foods by a stable isotope dilution assay using LC-MS-MS, J. Chromatogr. A, 1023 (2004) 57. 

A stable isotope dilution assay using mass spectrometry to measure insulin, proinsulin, and C-peptide has been developed. The difference in mass among the three analytes allows specific measurement of each protein. Comparison of patient samples revealed that most, but not all, results were higher by immunoassay than mass spectrometry. Thus immunoassays may overestimate insulin, particularly at low concentrations. The high protein concentration in the serum requires extraction of proteins (e.g., by immunoaffinity) and purification by high-performance liquid chromatography (HPLC) before quantification by mass spectrometry. This method is not suitable for routine laboratory analysis. 

Quantitative analysis also can be performed by a stable isotope dilution assay using d5-OTA as the standard (Lindenmeier et al., 2004 MacDonald et al., 1999). The 35Cl-containing [M+H]+ ion at m/z 404 and the 37Cl-containing analog at m/z 406 are monitored comparison between the m/z 404/406 peak area ratio in the sample with standard solutions provides an additional confirmation. 

Scherb J., Kreissl J., Haupt S., Schieberle P. Quantitation of S-methyhnethionine in raw vegetables and green malt by a stable isotope dilution assay using LC-MS/MS comparison with dimethyl... 

Majcenovic, A. B., Schneider, R., Lepoutre, J.-P., Lempereur, V., and Baumes, R. (2002). Synthesis and stable isotope dilution assay of ethanethiol and diethyl disulfide in wine using solid phase microextraction. Effect of aging on their levels in wine. /. Agric. Food Ghem. 50, 6653-6658. 

As discussed in [1], precise quantitative results will be obtained when a stable isotope dilution assay (SIDA) is performed. In this procedure, stable isoto-pomers of the analytes are used as internal standards. Consequently, the major effort in the development of SIDA is the synthesis of the labelled standards since most of them are not commercially available. 

Aubry, V., Etievant, P.X., Ginies, C., and Henry, R. 1997. Quantitative determination of potent flavor compounds in Burgundy pinot noir wines using a stable isotope dilution assay. J. Agric. FoodChem. 45 2120-2123. 

Guth, H. and Grosch, W. 1990. Deterioration of soya-bean oil Quantification of primary flavour compounds using a stable isotope dilution assay. Lebensm.-Wiss. Technol. 23 513-522. 

Schieberle, P. and Grosch, W. 1987. Quantitative analysis of aroma compounds in wheat and rye bread crusts using stable isotope dilution assay. J. Agric. Food Chem. 35 252-257. 

The measurement of odor intensity using OAVs is described by Grosch (1993, 1994). It requires the determination of the concentration of each odorant in the sample, and for those present in trace quantities, a stable isotope dilution assay must be used (Guth, 1997). This may make the determination of OAVs very tedious if many values are required. OS Vs are normalized peak areas from an odor chromatogram and represent a more realistic representation of the importance of the odors in a sample as perceived by the nose. Their determination is described by Acree (1997). 

Concentration of odorants in sample being analyzed, determined by use of internal standards, GC-MS in selected ion monitoring (SIM) mode or a stable isotope dilution assay for trace quantities (see unitgu). 

The caramel-like smelling HDF has been established as a main contributor to the flavors of several processed foods (Table 17). In addition, it should be noted that in all these foods, on the basis of a high FD-factor, HDF was also by far the most important caramel-like smelling odorant. In the following, the strategy in the HDF precursor analysis will be shown using wheat bread crust, popcorn [88] and malt as the examples. Quantitative measurements were performed by using a stable isotope dilution assay (cf. Section 3.2.). 

Kotseridis, Y., Baumes, R.L. Skouroumounis, G. (1999). Quantitative determination of free and hydrolytically liberated [J-damascenone in red grapes and wines using a stable isotope dilution assay. J. Chromatog., 849, 245-254. 

A suitable tool for the quantitation of trace compounds in foods is a stable isotope dilution assay (IVA) 16, 17). Allen et al. (18) used the IVA for the quantification of two methoxypyrazines in red wines, Guth (77) quantified wine lactone in various red and white wines and Aubry et al. (7P) used the technique for the determination of four esters (ethyl dihydrocinnamate, ethyl cinnamate, methyl anthranilate and ethyl anthranilate) in Pinot Noir wines. 

There are no convenient or reliable functional tests of pantothenic acid status, thus assessment is made by direct measurement of whole blood or urine pantothenic acid concentrations. Urine measurements are perhaps the easiest to conduct and interpret, and concentrations are closely related to dietary intake, Whole blood measurements are preferred to plasma, which contains only free pantothenic acid and is insensitive to changes in pantothenic acid intake. Concentrations of pantothenic acid in aU of the above fluids can be measured by microbiological assay, most commonly using Lactobacillus plantarum. Whole blood must first be treated with an enzyme preparation to release pantothenic acid fi om CoA. Other techniques that have been used to measure pantothenic acid in human samples include radioimmunoassay and gas chromatography, Other techniques that have been developed include gas chromatography-mass spectrometry and a stable isotope dilution assay. CoA and AGP can be measured by enzymatic methods. ... 

Figure 5.11. Mechanism of AAP formation proposed by Hoenicke (2002b). (Reprinted from Journal of Chromatography A 1150, Schmarr (2007) Analysis of 2-aminoaceto-phenone in wine using a stable isotope dilution assay and multidimensional gas chromatography-mass spectrometry, p. 79, Copyright 2006, with permission from Elsevier.)...

Identified by Blank et al. (1992a) in powder and brew of roasted arabica and robusta (with a lower concentration) coffees. Concentrations of 1.36-1.47 ppm in arabica (1.7 in a Kenya arabica by Grosch et al., 1996), 0.63 ppm in robusta were measured by Semmelroch et al. (1995) using stable isotope dilution assays. It was found in raw and medium-roasted arabica coffee (extraction, distillation, separation of acids) by Czerny and Grosch (2000) who gave concentrations of 0.7 ppb in green and 1.870 ppm in roasted coffee. 

Identified by Tressl et al. (1978a) who estimated its content at 50 ppm in roasted arabica, 25 in robusta and 35 in arabusta. Semmelroch et al. (1995) found concentrations of 109 ppm in arabica and 57 in robusta using stable isotope dilution assays. Silwar and Liillmann (1993b) noted that after 5 min of roasting, the concentration was higher at 230 °C than at 170 or 260 °C (ca 35 ppm). 

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