Isotope ratio analysis spectrometry method

Authenticity evaluation has recently received increased attention in a number of industries. The complex mixtures involved often require very high resolution analyses and, in the case of determining the authenticity of natural products, very accurate determination of enantiomeric purity. Juchelka et al. have described a method for the authenticity determination of natural products which uses a combination of enantioselective multidimensional gas chromatography with isotope ratio mass spectrometry (28). In isotope ratio mass spectrometry, combustion analysis is combined with mass spectrometry, and the ratio of the analyte is measured versus a... 

Of all the different mass spectrometric techniques for isotope analysis (such as ICP-MS, LA-ICP-MS, TIMS, GDMS, AMS, SIMS, RIMS and isotope ratio mass spectrometry of gases), the greatest proportion of pubhshed papers today concern ICP-MS with single and multiple ion collection.19 Due to its benefits, ICP-MS has now become a widely accepted method for isotope analysis and allows isotope ratios to be measured in a short time with good accuracy and precision.9,19,75 78 As discussed above, as a powerful and universal tool, ICP-MS has opened up new applications for isotope ratio measurements of elements with a high first ionization potential, which are difficult to analyze with TIMS (such as Mo, Hf, Fe). Of all the heavy metals studied, uranium was favoured by ICP-MS and LA-ICP-MS. 

More recently, enantiomer ratios have been used as evidence of adulteration in natural foods and essential oils. If the enantiomer distribution of achiral component of a natural food does not agree with that of a questionable sample, then adulteration can be suspected. Chiral GC analysis alone may not provide adequate evidence of adulteration, so it is often used in conjunction with other instrumental methods to completely authenticate the source of a natural food. These methods include isotope ratio mass spectrometry (IRMS), which determines an overall 13C/12C ratio (Mosandl, 1995), and site-specific natural isotope fractionation measured by nuclear magnetic resonance spectroscopy (SNIF-NMR), which determines a 2H/ H ratio at different sites in a molecule (Martin et al 1993), which have largely replaced more traditional analytical methods using GC, GC-MS, and HPLC. 

The results of the second interlaboratory study of PCN analytical methods using environmental matrices, undertaken by the US National Institute of Standards and Technology (NIST), should provide an indication of the comparability of published environmental PCN data and show where additional method enhancements are needed. Further method development efforts in the analysis of PCNs, and other complex mixtures are likely to focus on improving efficiencies by optimizing run times and separation. Examples may include time-of-flight mass spectrometry and multidimensional GC. New methods, such as isotope ratio mass spectrometry, may contribute to further source apportionment of complex mixtures [88]. 

Aguilera R, Becchi M, Casablanca H> Hatton CK, Gatlin DH, Starcevic B, et al. Improved method of detection of testosterone abuse by gas chromatography/combustion/isotope ratio mass spectrometry analysis of urinary steroids. J Mass Spectrom 1996 31 169-76. 

Fig. 6.12 Sample pretreatment and conversion of organic compounds into gases for isotope ratio mass spectrometry (IRMS). The reductive pyrolysis is normally performed on glassy carbon (for a summary see e.g. [ 1291). In case of coupled HPLC-IRMS for determination wet oxidation is used [ 122f In the routine isotope ratio analysis of water often isotope equilibration with gases are used for 0-analysis CO2 [ 130], for S H-analysis H2 gas in the presence of Pt [131]. Recently an on-line method for S O and in water has been described showing dual-inlet like performance [ 132]. Low-temperature pyrolysis in connection with GC is used for compound fragmentation with the aim of partial isotope pattern analysis [133]. TC-EA = thermo conversion elemental analyser...

Different protein-based methods have been reviewed for species identification in milk and dairy products, and for characterization of cheese maturity, such as electrophoretic, chromatographic, and immunological techniques (11, 12). In addition to new developments in these techniques, the interdisciplinary and dynamic nature of milk product analysis is being enhanced by the application of disciplines already used to analyze other foodstuffs. Among them, capillary electrophoresis (CE), polymerase chain reaction, and isotope ratio mass spectrometry are just gaining popularity for solving dairy authenticity problems (13-15). 

The coupling of SNIF-NMR with stable isotope ratio analysis/mass spectrometry has been the basis of a method for detection of adulteration of maple syrup with beet, cane, or com sugar.192 Adulteration of mustard oil by the addition of synthetic allyl isothiocyanate, its major component, is of economic interest, and therefore a combined NMR and mass spectrometry method was developed, enabling the distinction between the natural and the synthetic compound, as well as the determination of the geographical origin of natural mustard oils.193 Similar methods have been used for the analysis of flavourings such as vanilla flavour (vanillin and p-hydroxybenzaldehyde),194195 benzaldehyde,196 and others.197... 

Faulharber et al (5,6) and other researchers (7-9) have described how the determination of the isotope values of constituents is of increasing importance, especially in view of the demand for authenticity control and origin determination of essential oils and foods. To determine isotope values, g chromatography-isotope ratio mass spectrometry (GC-IRMS) has been used, although not widely. The present authors (70) have studied the possibility of a more convenient and common means of analysis of isotope values, based on the isotope peak in the mass spectrum of a compound. The present study focuses on the development of a new analytical method for the differentiation of quality in commercial citrus oils of various origins. 

Carbon isotope analysis on lake sediment cellulose may be performed by routine breakseal combustion (Boutton et al, 1983 Boutton, 1991a) or by continuous flow — isotope ratio mass spectrometry (CF-IRMS). Comparison of lake sediment samples analyzed by both methods at the UW-EIL show excellent agreement. 

McGaw, B. A., Milne, E. and Duncan, G. J. (1988) A rapid method for the preparation of combustion samples for stable carbon isotope analysis by isotope ratio mass spectrometry. Biomedical and Environmental Mass Spectrometry, 16, 269-73. 

D6866-04a Standard test methods for determining the bio-based content of natural range materials using radiocarbon and isotope ratio mass spectrometry analysis... 

Gavron A, Smith LE, Ressler JJ (2009) Nucl Instrum Methods Phys Res A 602(2) 581-587 Goldberg SA, Richter S, Schwieters H (2002) Improved environmental and forensics measurements using multiple ion counters in isotope ratio mass spectrometry, IAEA-CN-98/3/07. In International conference on advances in destructive and nondestructive analysis for environmental monitoring... 

Jasper, J.P., Edwards, J.S., Ford, L.C. (2001) A novel method for arson accelerant analysis gas chromatography/isotope ratio mass spectrometry, http // www.naturesfingerprint.com/pdfs/Arson%20Stable%20 Isotope % 20Analysis.pdf (accessed November 20,2011). 

Smith, C.I., Fuller, B.T., Choy, K., Richards, M.P. (2009) A three-phase liquid chromatographic method for 5 C analysis of amino acids from biological protein hydrolysates using liquid chromatography-isotope ratio mass spectrometry. Analytical Biochemistry, 390,165-172. 

ASTM D6866-06, Standard Test Methods for Determining the Biobased Content of Natural Range Materials Using Radiocarbon and Isotope Ratio Mass Spectrometry Analysis, American Society for Testing and Materials, 2006, p. 14. 

Method B Accelerator mass spectrometry (AMS) and isotope ratio mass spectrometry (IRMS) techniques to quantify the biobased content of a given product. Sample preparation methods are identical to Method A. Stored CO2 is sent to an AMS facility for final processing and analysis. The maximum error is 1-2% for AMS and 0.1-0.5% for IRMS. 

Thorinm-232 is the only non-radiogenic thorium isotope of the U/Th decay series. Thorinm-232 enters the ocean by continental weathering and is mostly in the particulate form. Early measurements of Th were by alpha-spectrometry and required large volume samples ca. 1000 T). Not only did this make sample collection difficult, but the signal-to-noise ratio was often low and uncertain. With the development of a neutron activation analysis " and amass spectrometry method " the quality of the data greatly improved, and the required volume for mass spectrometry was reduced to less than a liter. Surface ocean waters typically have elevated concentrations of dissolved and particulate 17,3 7,62... 

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