Results of four inter-laboratory comparisons provided by the Forensic Isotope Ratio Mass Spectrometry (FIRMS) network

Critique: Measuring Hydrogen Stable Isotope Abundance of Proteins to Infer Origins of Wildlife, Food and People

“…Not surprisingly therefore, ILC samples of horse hair and paper that had been allowed to equilibrate with ambient humidity in the participating laboratories, yielded Huber estimates of the mean values (H15) of d 2 H total associated with H15 SDs of ±11.1 and 7.4 ‰, respectively [76]. Differences between lowest and highest d 2 H total values from the corresponding H15 mean values for horse hair and paper were 44.3 and 21.3 ‰, respectively [75]. Considering that within-laboratory SD for either material were typically 2.0 and 1.4 ‰, it was clear external factors, such as laboratory specific differences, most likely differences in sample preparation, as well as geographic location and related differences in the isotopic composition of ambient humidity, were amongst the factors contributing to these findings.…”

“…Tap water [71] VSMOW Human hair (values determined using IUPAC guidelines) [52] Human hair [71] 34 ‰ Measuring hydrogen stable isotope abundance to infer origins of wildlife, food & people | PersPective www.future-science.com Ambient humidity at the point of origin is -65 ‰ too, so its total d 2 H value as measured at this location would also be -65 ‰. Published data put the typical exchange fraction of finely chopped hair at ambient at 0.1 [47,48,54] ues vary greatly if participating laboratories did not determine or correct for the molar exchange fraction of these materials as part of the ILC [75]. Not surprisingly therefore, ILC samples of horse hair and paper that had been allowed to equilibrate with ambient humidity in the participating laboratories, yielded Huber estimates of the mean values (H15) of d 2 H total associated with H15 SDs of ±11.1 and 7.4 ‰, respectively [76].…”

“…This conclusion was supported by the ILC results for a material with no exchangeable H that were reported in the same paper. For polyethylene foil [-CH 2 CH 2 ] n , the values for H15 SD and within-laboratory SD were 2.2 and 1.3 ‰, while the range around the H15 mean was 4.6 ‰ [75].…”

Global spatial distributions of nitrogen and carbon stable isotope ratios of modern human hair

“…[46] However, inter-laboratory comparisons of EA/IRMS measurements of organic substances showed results that varied by up to ±1 ‰ for carbon and up to more than ±1 ‰ for nitrogen isotope ratios compared with the mean value. [47] Consequently, such variances in isotope ratios have to be assumed in the presented dataset and would lead to higher estimated over-all variances on the one hand and to potential biases in the dataset on the other. In addition, over the period of several decades different (secondary) isotopic reference materials have been used for normalisation of the measurement methods.…”

Development of Alditol Acetate Derivatives for the Determination of 15N-Enriched Amino Sugars by Gas Chromatography–Combustion–Isotope Ratio Mass Spectrometry

“…The alditol acetate derivatisation method for amino sugars was adapted from that reported by Whiton et al 25 Briefly, dried amino sugar residues were reduced with sodium borohydride (500 µl, 100 mg ml -1 in DDW) and heated (60 °C, 2. 40 as normalisation standards and phenacetin (-8.4 ±0.4 ‰) 39 or IAEA-305-A (ammonium sulphate; 39.8 ±0.5 ‰) 40 as quality control materials. Benzocaine and phenacetin standards were distributed during proficiency tests organised by the Forensic IRMS network.…”