Flash ht plus

The carbon and nitrogen isotope composition ratios (¹³C/¹²C and ¹⁵N/¹⁴N respectively) of Argan oil samples (around 0.3 mg of oil) were determined via continuous flow EA-IRMS using an isotope ratio mass spectrometer (Delta V Thermo Scientific, Germany) coupled to an element analyzer (Thermo Scientific FLASH HT Plus) following the procedure described by Taous et al. [22 (link)].
The relative difference of isotope ratios (isotope-delta values) of a sample is reported according to the following formula [27 (link)]:
where i is the mass number of the heavier isotope of element E, R_SA is the respective isotope ratio of the sample and R_REF is the relevant internationally recognized reference material. The delta values were multiplied by 1000 and expressed in units “per mil” (‰).The isotopic δ¹⁵N‰ and δ¹³C‰ values of the samples were calibrated versus the following certified reference materials: fuel oil NBS-22 (δ¹³C (‰) = −30.031 ± 0.043), benzoic acid IAEA-601(δ¹³C (‰) = −28.81 ± 0.04‰) and Caffeine IAEA-600 (δ¹⁵N (‰) = +1 ± 0.2‰) (Provided to CNESTEN by IAEA under CRP N° D052040). Uncertainty per batch (7 replicates of secondary isotopic reference material) was ≤1.4‰ for δ¹³C and ≤0.7‰ for δ¹⁵N.

All samples were processed at iThemba Laboratories (Johannesburg, South Africa) on a Flash HT Plus elemental analyser, coupled to a Delta V Advantage isotope ratio mass spectrometer by a ConFloIV interface (all supplied by ThermoFisher, Bremen, Germany), to determine carbon (¹³C and ¹²C) and nitrogen (¹⁵N and ¹⁴N) concentrations and ratios. SI data are represented as the relative (‰) difference between samples and the international standard for C (Pee Dee Belemnite carbonate) and N (atmospheric N₂):

where X is ¹³C or ¹⁵N and R is the ¹³C:¹²C or ¹⁵N:¹⁴N ratio. SI values were corrected against a standard of known concentrations (Merck Gel), which was run after every 12 or 24 unknown samples. The 1σ precision of all standards (n = 62) was ±0.10‰ and ±0.08‰ for C and N, respectively.

Total C and N and their isotope composition (δ¹³C and δ¹⁵N, respectively) in soil and sporocarps were determined by elemental analysis and isotope ratio mass spectrometry (EA/IRMS) system by means of Flash HT Plus elemental analyser coupled to a Delta-V Advantage isotope ratio mass spectrometer via a CONFLO IV interface (Thermo Fisher Scientific, Bremen, DE). The analytical measurement errors were ±0.1‰ for δ¹³C and ±0.2‰ for δ¹⁵N. Total C was organic C due to the absence of carbonates in the study area^{76 (link)}.