Comparison of liquid chromatography–isotope ratio mass spectrometry (LC/IRMS) and gas chromatography–combustion–isotope ratio mass spectrometry (GC/C/IRMS) for the determination of collagen amino acid <i>δ</i><sup>13</sup>C values for palaeodietary and palaeoecological reconstruction

107

This derivatization method is a rapid means of determining carbon and nitrogen isotopic ratios of amino acids present in the biological materials often sampled for ecological studies. While amino acids with charged or polar side chains do not have uniformly high recoveries, the average precision of measurements is comparable with that of other, more established methods. Batches of samples may be prepared from many raw materials in less than a day, representing a significant reduction in preparation time over prevailing methods.

Section: Comparison Of the Reaction Times And Steps Required For Widementioning

confidence: 99%

Compound‐specific δ¹³C and δ¹⁵N analysis of amino acids: a rapid, chloroformate‐based method for ecological studies

Walsh

Yarnes

2013

107

“…A number of previous studies have described the stable carbon isotopic analysis of individual amino acids, typically derived by hydrolysis of proteins, from various biological sources . This compound‐specific isotope analysis (CSIA) is achieved either by gas chromatography of derivatised amino acids coupled with isotope ratio mass spectrometry (IRMS) or by high‐pressure liquid chromatography (HPLC) of underivatised amino acids coupled to IRMS using chemical oxidation to convert the carbon present in organic compounds into CO 2 (LC/CO/IRMS) . The use of LC/CO/IRMS for CSIA is now a relatively mature technique, especially with regard to the separation of underivatised amino acids using mixed‐mode HPLC columns and aqueous mobile phases .…”

Section: Introductionmentioning

confidence: 99%

Position‐specific ¹³C/¹²C analysis of amino acid carboxyl groups – automated flow‐injection analysis based on reaction with ninhydrin

Fry

Carter

Yamada

et al. 2018

RationaleThe fundamental level of stable isotopic knowledge lies at specific atomic positions within molecules but existing methods of analysis require lengthy off‐line preparation to reveal this information. An automated position‐specific isotope analysis (PSIA) method is presented to determine the stable carbon isotopic compositions of the carboxyl groups of amino acids (δ 13CCARBOXYL values). This automation makes PSIA measurements easier and routine.MethodsAn existing high‐performance liquid chromatography (HPLC) gas handling interface/stable isotope ratio mass spectrometry system was modified by the addition of a post‐column derivatisation unit between the HPLC system and the interface. The post‐column reaction was optimised to yield CO2 from the carboxyl groups of amino acids by reaction with ninhydrin.ResultsThe methodology described produced δ 13CCARBOXYL values with typical standard deviations below ±0.1 ‰ and consistent differences (Δ 13CCARBOXYL values) between amino acids over a 1‐year period. First estimates are presented for the δ 13CCARBOXYL values of a number of internationally available amino acid reference materials.ConclusionsThe PSIA methodology described provides a further dimension to the stable isotopic characterisation of amino acids at a more detailed level than the bulk or averaged whole‐molecule level. When combined with on‐line chromatographic separation or off‐line fraction collection of protein hydrolysates the technique will offer an automated and routine way to study position‐specific carboxyl carbon isotope information for amino acids, enabling more refined isotopic studies of carbon uptake and metabolism.

“…Within‐laboratory investigations of different methodologies are more common, but have largely focused on δ 13 C‐AA measurements (e.g. ) and the effect of exogenous carbon on measurement accuracy and error propagation . Meanwhile, comparisons of δ 15 N‐AA data across laboratories are scarce; even comparisons within the same laboratory have been rare (however, see ) ).…”

mentioning

confidence: 99%

The relative influence of derivatization and normalization procedures on the compound‐specific stable isotope analysis of nitrogen in amino acids

Yarnes

Herszage

2017

The overall accuracy and precision of δ N-AA measurements were improved following both compound-specific calibration and scale-normalization, as was the comparability of δ N-AA measurements of individual amino acids between derivatization techniques across organisms. The mean difference of scale-normalized δ N-AA values across all organisms between the two derivatization techniques was 0.19‰, much less than the typical analytical error associated with δ N-AA measurements (±1‰) CONCLUSIONS: Adoption of standardized calibration procedures will be important to establishing reproducibility in δ N-AA measurements, particularly across derivatization techniques. It is both technically practical and desirable for users of CSIA-AA to adopt practices in quality control and assessment similar to those outlined for BSIA, including the compound-specific calibration of δ N-AA values, followed by scale-normalization. Copyright © 2017 John Wiley & Sons, Ltd.