Simultaneous N, C and S Isotope Ratio Determination on a DELTA V Isotope Ratio MS using a Flash Elemental Analyzer Oliver Kracht, Thermo Fisher Scientific, Bremen, Germany Introduction Key Words • ConFlo IV • DELTA V Series • Elemental Analyzer • smartEA™ • Multi-Element Analysis • Isotope Ratio MS Multi-element isotope ratio analysis is becoming increasingly important, particularly in food authenticity control and forensic applications. With increasing numbers of samples for analysis, reduced sample preparation and measurement time are required. The ability to measure N, C and S isotopes from a single sample drop was demonstrated by Avak in 1996 with an analysis time of 30 minutes.1 With the introduction of the Thermo Scientific ConFlo IV universal interface in July 2007, the ability for multi-element isotope ratio determination was both enhanced and simplified. The ConFlo IV interface allows software-controlled switching of up to five reference gases and Figure 1: N, C and S triple measurement of sulfanilamide. Top: mass traces, middle: TCD trace of automatic dilution of sample gases down Flash EA, bottom: tabs with comprehensive data and results for each isotope. to 1:100 according to the varying amounts FlashEA 1112 settings NCS triple analysis of the three elements in the samples. Using the Thermo Reactor temperature 1,020 °C Scientific smartEA option, the simultaneous analysis of N, GC temperature 70 °C Carrier flow 80 mL/min C and S is simplified even further. The smartEA™ option Autosampler type MAS 200R adjusts the dilution of sample gases as a direct response to Table 1: System settings for triple measurement. the TCD signals from the Flash Elemental Analyzer (EA). The optimized chromatography now reduces the analysis The ConFlo IV universal interface and the Flash EA time to less than 18 minutes. were connected with the smartEA™ option to make use of This technical note explains the modifications needed the automatic dilution ability. The isotope ratio mass for triple measurements of N, C and S isotope ratios and spectrometer (IRMS) used was a Thermo Scientific DELTA shows the performance that can be achieved. V Plus with a universal triple collector. A fast magnet field jump of the IRMS takes place automatically between the Method N2 and CO2 peaks followed by a slow magnet field jump Optimal conditions for sulfur isotope ratio analysis require to SO2. a short transfer line and reduced volumes in a water-free environment. Therefore a single reactor filled with WO3 Results and electrolytic copper wires is used for the triple N, C and The chromatogram in Figure 1 shows flat top reference gas S analysis. A chemical trap of magnesium perchlorate pulses from the ConFlo IV interface and the chromaremoves water produced in the combustion process. Tubing tographically separated sample peaks of N2, CO2 and SO2 in the Flash EA and the connection to the ConFlo IV from the elemental analyzer (400 µg of sulfanilamide). N2 interface is made of 1/16” Sulfinert® capillary to avoid the and CO2 show a separation of 17 seconds which is required formation of acidic compounds by SO2 with adsorbed to perform a fast magnet field jump immediately after the water. The commonly used Teflon® tubing cannot be used detection of the N2 sample peak at 191 seconds. The for triple analysis of N, C and S due to increased nitrogen change of the magnet field from CO2 to SO2 is performed background. An optimized chromatographic column slowly between the CO2 and SO2 reference gas pulses at separates N2 and CO2 with an improved retention time of 460 seconds. the SO2. The Flash elemental analyzer used was a Thermo Scientific FlashEA 1112, system paramete

Sample Identifier Sulfanilamide Sulfanilamide Sulfanilamide Vitamin B1 Vitamin B1 Vitamin B1 Vitamin H Vitamin H Vitamin H Cysteine Cysteine Cysteine Soil Soil Soil Octopus Tissue Octopus Tissue Octopus Tissue Bird Feather Bird Feather Bird Feather Pesticide Pesticide Pesticide River Sediment River Sediment River Sediment Conclusion The triple analysis of N, C and S isotopes can be performed with any DELTA V series mass spectrometer using a Flash elemental analyzer for IRMS with a sulfur applicable reactor, tubing, and a chromatographic column described in Table 3. It is recommended to use Sulfinert...