DI-IRMS

The purpose of this paper was to briefly describe fundamentals of isotope ratio mass spectrometry (IRMS), review the analytical systems currently available both for traditional dual-inlet (DI-IRMS) and the newer continuous-flow (CF-IRMS) and describe the specialized instruments that are in general use for isotopic measurements. 

CF-IRMS provides reliable data on micromoles or even nanomoles of sample without the need for cryogenic concentration because more of the sample enters the ion source than in DI-IRMS. CF-IRMS instruments accept solid, liquid, or gaseous samples such as leaves, soil, algae, or soil gas, and process 100-125 samples per day. Automated sample preparation and analysis takes 3-10 min per sample. The performance of CF-IRMS systems is largely determined by the sample preparation technology. A variety of inlet and preparation systems is available, including GC combustion (GC/C), elemental analyzer, trace gas pre-concentrator and other. The novel... 

There are now a number of options open to scientists who need to analyse stable isotopes as part of their research. The choice is dependent on many factors, such as the type of sample, the precision of measurements required, the amount of sample available, and the number of samples to be analysed. Dual inlet IRMS is still the technique of choice those scientists who need to measure a few samples to very great precision. More often, scientists want to determine a trend in conditions over time, or a flux integrated over an area. In these cases, CF-IRMS will be preferred. Continuous-flow IRMS is also preferred when a limited amount of sample material is available, as it is able to analyze far smaller samples (between 10 and several hundred times smaller) than DI-IRMS. 

Dual-inlet isotope ratio mass spectrometry (DI-IRMS) ... 

The analysis of the isotopic composition of explosives dates back to a publication by Nissenbaum in 1975 [101]. The carbon isotopic compositions of TNT samples from different countries were determined using DI-IRMS, where the results indicated that the different TNT samples could be differentiated. Potential sources for the observed variation in the carbon isotope values were discussed, for example, isotopic composition of the starting materials and country of origin. 

Dempster et al. [126] and Harrington et al. [127] demonstrate using GC-IRMS and DI-IRMS, respectively, that commercially available BTEX can have a wide range of carbon isotope values and that these values are different for samples from different manufacturers. 

Liu et al. [156] conducted research on the carbon isotopic composition of Cannabis saliva L. (i.e., cannabis) samples from different geographical origins and grown under different conditions. The authors did not achieve individualization of the cannabis samples analyzed using DI-IRMS however, they concluded that this technique, used in combination with traditional methods, could be useful for increased differentiation. 

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