Cornell-Boyce Thompson Stable Isotope Laboratory

Finnigan MAT Delta Plus

COIL houses a Finnigan MAT Delta Plus that was purchased in 1997. This isotope ratio mass spectrometer (IRMS) has the ability to measure samples for ¹³C and ¹⁵N through continuous flow. Currently, the instrument is plumbed to a Carlo Erba NC2500 elemental analyzer through a Conflo II open split interface for elemental and isotopic composition of solid samples. The elemental analyzer is equipped with an AS200 auto-sampler that has a capacity of 99 samples and standards.

H/D and ¹⁸O measurements from liquid samples are measured using a GFL 1086 water equilibrator. This unit is capable of robust isotope ratio measurements via a process known as dual inlet analysis. 24 samples can be analyzed during the course of a sample run using 3 ml aliquots. From this one aliquot, both hydrogen and oxygen measurements can be made. Hydrogen analysis requires the use of hoko sticks for accurate isotopic measurement.

Measurement of gas samples is done on the tube-cracker multiport system. The multiport is another form of dual inlet analysis that can measure prepped samples for N₂, CO₂, and H₂ gases. These samples must be vacuum-sealed in glass tubes. COIL has the extraction lines, which are utilized for most multiport sample needs.

Delta Plus Specifications

Mass Range:
1-70 dalton at 3 KV
Resolution:
CNOS: M/deltaM = 95 (10% valley definition)
H/D: M/deltaM = 10 (10% valley definition)
Sensitivity (absolute):
1500 molecules CO₂ per mass 44 ion at the collector with high Helium flow (1500 molecules/ion)
Ion Source Linearity:
0.02‰/nA ion current (mass 44)
Sample Consumption (typical):
0.15 nmol/s CO₂ for 10 nA signal at mass 44 (10-2)

The Europa Geo 20-20 dual-inlet gas isotope ratio mass spectrometer provides the ultimate precision and sensitivity in stable isotope measurement of a wide range of gases. High precision analysis combined with a range of sample preparation modules gives the Geo 20-20 the flexibility to adapt to a wide range of applications. These include geochemistry, hydrology, environmental, marine and biological sciences; in fact any application where ultimate IRMS performance is a necessity.

A universal faraday collector with three buckets gives improved flexibility for measurement of a wide range of isotope ratios. The triple collector allows simultaneous collection of adjacent masses in range 28, 29, 30 – 64, 65, 66 with no adjustment of either the collectors or the amplifiers. This simplifies changing between gas species.

The ANCA-SL offers a proven combustion interface for analysis of ¹³C, ¹⁵N, and ³⁴S in bulk materials by ANCA-IRMS. ¹³C and ¹⁵N can be measured from the same sample. An ANCA-TG is available for trace gas measurements of N₂ and CO₂. A Gilson autosampler allows for rapid and precise analysis of multiple gas samples in exetainers. A Dual Inlet Multiport is configured for analysis of gases that are prepared offline.

Analyser:
5 KV maximum acceleration voltage, permanent or electromagnet CNOS; 120 degree sector, 11 cm radius, stigmatic focusing, extended geometry giving effective 20.9 cm radius dispersion.
Pumping System:
True differential pumping giving at least one order of magnitude reduction in pressure from ion-source housing to analyzer. High vacuum measurement by filament-free inverted magnetron gauges.
Ion Source:
Nier-type, virtual image, electron impact with Th coated Ir filament and magnetic electron collimation.
Collector:
All collectors are of deep Faraday bucket design and fully shielded. Secondary electron emission is suppressed by electric field.