stable isotopes (4)

10893906085?profile=RESIZE_710xIsotope ratio data are increasingly used in a variety of fields including, ecology, marine sciences, earth and geosciences, forensic science, hydrology, medicine, food (including food authenticity and origin), and climate science.
 
Over the years, there have also been changes to guidelines for measurement methods, calibration conventions and even to international measurement standards that form the base of the traceability chain for isotope delta values for H, C, N, O and S.
 
It is impossible to combine isotope ratio data from a variety of sources unless the data are accompanied by a clear description of traceability and other method details.

The UK National Measurement Laboratory at LGC was part of an international group that compiled the IUPAC Technical Report presenting minimum requirements for reporting isotope ratio data, covering analytical procedure, traceability, data processing and uncertainty evaluation.

This report will help in the standardisation of methods that involve the measurement of stable isotopes.

Read the IUPAC Technical Report on minimum requirements for publishing hydrogen, carbon, nitrogen, oxygen and sulfur stable-isotope delta results.

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Information on the geographic origin of milk is important in determining quality attributes, and for economic gain through building brand value associated with origin. Stable isotope signatures and trace element concentrations are being increasingly used to authenticate milk, though information on the suitability of such technology to verify the agroclimatic origin in small continents with diverse climatic, environmental conditions, and animal management practice is scarce. The objective of this study was to investigate the possibility of using a stable isotope composition of C, N, O, and H and elemental fingerprints to determine the origin of milk produced in different agroclimatic zones of Sri Lanka.Stable isotopes ratios of C, N, H, and O, and elemental fingerprints of milk samples were determined by IRMS and ICP-MS, respectively. Significant variations were observed in stable isotope ratios, especially δ18O and the mean content of Li, Al, Cr, Mn, and Sr in the bulk milk samples obtained from different agroclimatic zones. A linear discriminant analysis differentiated cow milk produced from four agroclimatic zones based on stable isotope ratios, and the inclusion of elemental ratios enhanced the discriminating ability. 

Read the full open-access paper here

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6520790083?profile=RESIZE_584xThe season when tea is harvested, as well as the age of the tea can affect its quality, hence authenticating the season/age of high cost teas can be desirable. Chinese researchers have used trace elements and stable isotopes with chemometrics to characterise Pu'er tea according to its production year. Pu'er tea is prepared by drying green Chinese tea, then subjecting it to a microbiological fermentation by naturally occurring moulds, bacteria and yeasts. The tea is then pressed into a variety of shapes.

A total of 86 mineral elements and stable isotope compositions were determined from the Xiangzhujing Pu'er tea in five different production years. Different chemometric techniques were applied to find the best models to predict the production year.  Mn,68Zn, and 203Tl were the best authenticity markers for enabling the successful authentication of Pu'er tea with different production years. 

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Researchers at the University of Southampton have derived carbon and nitrogen stable isotopic isoscapes using jellyfish from different locations around the North Sea. These were applied to scallops and herring, enabling 75% of scallops origin to be confirmed within an error of 10 sq.km.  

It was also possible to assign location of migratory fish such as herring with the isoscapes, but with some reduced accuracy. The isotopic method compares favourably with other methods used to determine location of seafood in the North Sea. 

Read the full paper at: http://onlinelibrary.wiley.com/doi/10.1111/2041-210X.12651/full

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