The miniRUEDI will see any gas species with mass-spectrometric peaks at m/z values of 200 or lower (special miniRUEDI versions can be built that will go up to m/z = 400). The miniRUEDI has been used successfully to quantify He, Ne, Ar, Kr, Xe, N₂, O₂, H₂, CO₂, CH₄, and C₃H₈ in different gas matrices (air, CO₂ or CH₄ seeps, technical gas mixtures, etc.).

Specific considerations:

• Typical limits of quantification (LOQ) are listed below.
• To quantify a gas species X in a gas sample, a reference standard with a known concentration of X is required for calibration of the measurement (see also below).
• It is well known that some gas species may interfere with each other during analysis in the mass spectrometer. The miniRUEDI software provides tools to compensate such interferences and determine accurate analysis results even in the presence such interferences (see here).

To quantify the partial pressure or concentration of a gas species X in a sample, the raw measurement data needs to be calibrated relative to a standard gas with a known partial pressure of X. Ideally, the partial pressure of X in the standard should be similar to those in the samples to within one or two orders of magnitude.

For many gas species (e.g., He, Ne, Ar, Kr, N₂, O₂), air may serve as a convenient and very well-defined standard. Air standards can usually be sampled directly from ambient air.

For other gas species with very low or variable/unknown atmospheric partial pressures (e.g., Xe, CO₂, CH₄, DMS, etc.), dedicated standard-gas mixtures are required. Such gas mixtures can be acquired from specialised companies, or may be manufactured in-house. The standard gases should be kept in flexible, gas-tight bags to avoid depressurisation of the standard gas while it is consumed by the miniRUEDI. We recommend gas bags made of metallized foil. Please avoid gas bags equipped with plastic valves, which are prone to leakage. Stainless-steel “straight-through” tube connectors with a Swagelok SS-4H or similar valve are preferred. Carefully purge and evacuate the gas bags before filling them with the standard gas.

The following table lists typical LOQ values for selected trace-gas species in an air-like sample matrix (20% O₂, 79% N₂, 1% Ar, water vapour). Note that the LOQ values may be different in other gas matrices.

Notes:
(a) Requires interference compensation (see here)
(b) Estimated value, needs systematic testing

Yes, see here.

The miniRUEDI itself requires hardly any routine maintenance. After years of use, the MS filament and the multiplier detector may need replacement, and the pumps may benefit from servicing the membranes and bearings.
The GE-MIMS modules may need drying of condensation in the gas headspace from time to time. Also, suspended particles in the water flow may collect on the inflow to the membrane module and need to be cleaned out from time to time to prevent clogging of the membrane hollow fibers (see also note about particle filters below).

If the sampled water is loaded with suspended particles, a filter is useful to prevent clogging of the GE-MIMS module. We recommend large-volume and re-usable filter cartridges with a mesh size of 20 µm or smaller (for example Nussbaum part number 18095.22). Make sure the filter does not trap any air or other gas bubbles, which would affect the dissolved gas concentrations of the sampled water.

Yes, see here.