Selective Detection of Volatile Aromatic Compounds Using a Compact Laser Ionization Detector with Fast Gas Chromatography

Abstract

We report results for a new gas chromatography detector that is comparatively sensitive and far more selective for aromatic compounds than the traditional photoionization detector. The detection means is multiphoton ionization at atmospheric pressure. The ionization source in these experiments is a diode-pumped passively Q-switched microchip laser operating at 266 nm. Experiments were conducted with the detector interfaced to a fast gas chromatograph. For <20 s elution time, limits of detection were <1 pg for toluene, ethylbenzene, xylenes, and isopropylbenzene; the limit of detection for benzene is approximately 10 pg. Detector response was linear over 5 orders of magnitude, including these low levels. Negligible signals were observed for nonaromatic ketones, aldehydes, ethers, and cycloalkanes at levels as high as 0.1 microg (10 mg/L concentration). Detector efficiency after fast GC separation was 0.002% when using a detector cell with a radius of 1.1 cm and a purge gas flow of 500 mL/min. The advantages of this detector are further illustrated by the fast GC analysis of fuel samples.

Hyper-fast gas chromatography and single-photon ionisation time-of-flight mass spectrometry with integrated electrical modulator-based sampling for headspace and online VOC analyses

“…Please do not adjust margins Please do not adjust margins which is set in relation to the standard gas of 1 ppm. From 10 consecutive chromatograms, we obtain 2 ppb for toluene and 0.5 ppb for p-xylene, which is competitive with LODs from previously published fastGC setups with soft ionization mass spectrometry 9,17,18 or fast GC with sensor array detection 6 for analytes of similar volatility. It has been found that the photoionisation cross section at 126 nm of p-xylene differs by less than 25% of the one of toluene 19 , we attribute the lower LOD of p-xylene to the highe r trapping efficiency.…”