Gas chromatography combined with fast flow glow discharge mass spectrometry (GC-FFGD-MS)

Abstract

A low power (v5 W) dc fast flow glow discharge (FFGD) ion source has been adapted for the detection of halogenated hydrocarbons using gas chromatography as the sample introduction technique. A simple and robust interface design enabled direct coupling of the ion source to a common gas chromatograph. After optimisation, detection limits for four compounds were from 0.3-66.5 pg (by monitoring the halogen ions 35 Cl, 79 Br and 127 I). The source operating conditions can be 'tuned' to obtain different information, allowing both sensitive elemental detection and structure elucidation using a single instrument, with sub-pg detection limits for the bromobenzene molecular ion. The source pressure, power and discharge gas flow rate were found to have significant effects on the relative fragment ions detected. These observations can be rationalised using neutral, excited state chemistry.

Organic mass spectrometry and control of fragmentation using a fast flow glow discharge ion source

“…It has been shown previously26, 27 that using a relatively low energy plasma for ionization helps to minimize sample fragmentation (as expected): when P was 1.00 Torr, F was ≤400 sccm (corresponding to τ = 1.4 to 2.8 ms) and V d was 700 V (giving I d values between 0.8 and 1.7 mA). The relative ion signal intensities and fragmentation patterns were also found to have a strong dependence on the bias applied to the sampling cone.…”

“…Previously,26, 27 we have used a GC inlet system for observing mass spectra of organic and organometallic compounds. The transient nature of the ion signals when using GC for sample introduction required time‐resolved analysis (TRA package on PQVision 4.4, Thermo Electron).…”

“…1:100 between two lengths of 100% methyl‐deactivated fused‐silica tubing (0.25 mm i.d.). The sample flow was introduced into the ion source using the GC interface previously described 26. The split flow was removed from the inlet system by an Edwards E2M5 rotary pump.…”

“…By using a rapid flow of the discharge gas, the analytical signal was boosted due to an increase in the sample erosion rate and a reduction in diffusional losses of cathode material to the internal surfaces of the source. The FFGD technique has also been used as a very sensitive detector for GC/MS measurements of halocarbon26 and organotin compounds 27. It is a convenient and robust method for the analysis of organic vapors because the samples are analyzed ‘downstream’ from the main discharge (which is close to the cathode).…”

Plasma-source mass spectrometry for speciation analysis: state-of-the-art

“…Recently, Manson et al [200] combined GC with a fastflow glow discharge (FFGD) for mass spectrometric detection. The dc-FFGD consists of a pin-type GD cathode positioned coaxially with the sampling orifice of the mass spectrometer.…”