Towards a universal ion source: Glow Flow mass spectrometry

A helium-microplasma ion source (Glow Flow) has been developed and characterised. It is engineered to be a simple design, of low-cost and can be readily retrofitted to most modern mass spectrometers. Initial assessment of its performance has shown it to be robust, reproducible and of high sensitivity. Glow Flow provides broad non-specific detection of samples from polar through to non-polar chemistries making it of wide utility. A study of persistent organic pollutants, polyaromatic hydrocarbons, low average-molecular-mass polymers (polyethyleneimine, polyethylene glycol, and polypropylene glycol) and a complex mixture of fatty-acid methyl esters by direct sample introduction using a nebulised heated nitrogen flow was conducted. The ability to make quantitative measurement was investigated using methyl stearate and a linear calibration plot gave a R2 = 0.999 and limit-of-detection of ∼100 fmol. This design is extremely stable, in operation. Typical ions commonly observed are intense protonated molecule ions, radical molecular ions, hydride abstracted ions, and oxygen adduct ions. At present this system is valuable to apply to small molecule analysis (m/z < 1000), and is easily interfaced to gas and liquid chromatography, and likely to be useful for imaging.