The use of multi‐element stable isotope analysis to monitor the origin of chondroitin sulfates

Abstract

Continuous-flow isotope ratio mass spectrometry (CF-IRMS) of deuterium, carbon, nitrogen, oxygen and sulfur has been used to analyse samples of pure chondroitin sulfates from known animal sources (shark, squid, salmon, pig and bovine). There is a need to control the origin of this dietary supplement, which is extracted from several types of animals: for traditional, ethical, or economic reasons, a given source of natural products of animal origin can be preferred to another, and can therefore have a different price. Twenty-three samples collected in Europe and Asia were analysed by IRMS. The results, especially the isotopic deviations of sulphur, oxygen and deuterium, show a significant discrimination between marine and terrestrial origins of this compound which will provide a convenient and efficient way to control the declared sources in the market. The differences observed between origins are further discussed.

Anion-Specific Sulfur Isotope Analysis by Liquid Chromatography Coupled to Multicollector ICPMS

“…In addition, avoiding sample-standard bracketing enhances sample throughput and may be useful for samples for which matrix matching remains difficult. The developed LC-MC-ICPMS method allows the analysis of δ 34 S in sulfite, sulfate and thiosulfate in a single chromatographic run with a reproducibility better than 0.3‰ for sulfite and sulfate and better than 0.5‰ for thiosulfate for 1 μg of injected sulfur (per species); these reproducibilities are close to those obtained by EA-IRMS (0.1–0.5‰). ,, This online method considerably simplifies the analysis of environmental water samples since sample preparation and purification steps are no longer required and the time of analysis is reduced. Notably, only 1 μg-S is required, whereas the minimum amount for EA-IRMS is 33 μg-S …”

“…The developed LC--MC--ICPMS method allows the analysis of δ 34 S in sulfite, sulfate and thiosulfate in a single chromatographic run with a reproducibility better than 0.3‰ for sulfite and sulfate and better than 0.5‰ for thiosulfate for 1 µg of injected sulfur (per spe-cies); these reproducibilities are close to those obtained by EA--IRMS (0.1--0.5‰). 22,25,40 This online method considera-bly simplifies the analysis of environmental water samples since sample preparation and purification steps are no longer required and the time of analysis is reduced. Nota-bly, only 1 µg--S is required, whereas the minimum amount for EA--IRMS is 33 µg--S. 38 The application of our innovative methodology to synthetic solutions and environmental water samples shows the high accuracy achievable and points out the limitation of the method.…”

Ignoring IUPAC guidelines for measurement and reporting of stable isotope abundance values affects us all

“…δ values relative to VPDB or VSMOW yet without formally meeting IUPAC guidelines [2] can be found not just in this journal, but in equally wellrespected journals such as Food Chemistry, Forensic Science International, The Journal of Food & Agricultural Chemistry or The Journal of Paleolimnology, to name but a few. [6][7][8][9][10][11] In the following we shall use the aforementioned article [1] solely as an example how stable isotope methodology as described there falls short of IUPAC guidelines. [2] In their article the authors state the following: [1] "The isotope ratio values are expressed in δ‰ (= [(Rsample -Rstandard)/ Rstandard] * 1000, where R is the ratio between the heavier isotope and the lighter one) against international standards (Vienna-Pee Dee Belemnite (V-PDB) for δ 13 C values, and Vienna-Standard Mean Ocean Water (VSMOW) for δ 2 H and δ 18 O values).…”