Gas Chromatography with Atomic Emission Detection in Environmental Analysis

Abstract

When capillary gas chromatography (GC) is coupled with atomic emission detection (AED), mixtures of volatile and semivolatile organic compounds are first separated based on different retention in a capillary GC column, whereafter the separated compounds are introduced directly into a helium (or argon) plasma. The high temperature of this plasma results in atomization of the separated compounds followed by excitation of the constituent atoms. From the excited states, the atoms emit light of characteristic wavelengths which are monitored continuously during the chromatographic separation by an optical spectrometer. This results in element‐selective chromatograms, where all elements from the periodic table (except helium or argon) may be monitored selectively with a simple change of wavelength on the spectrometer. With the use of multichannel spectrometers, several elements may be monitored simultaneously resulting in multielemental detection. Both nonmetallic and metallic elements are detected with a very high selectivity. This enables environmental contaminants containing heteroatoms to be determined in dirty extracts without extensive sample cleanup. However, since detection limits (DLs) in GC/AED range from 1–100 pg s −1 , extensive analyte enrichment is often required prior to environmental analysis. Because the separated compounds are atomized within the plasma, only minor structural variations are observed for the detector responses. This, in combination with the multielemental capability, enables estimation of empirical formulas for each of the separated compounds, which may be utilized to support identification of environmental micropollutants. In addition, the structure‐independent detector responses enable simplified calibration for quantitative purposes because different compounds may be quantified based on a single elemental calibration curve.

Direct Measurement of Elemental Mercury Using Multidimensional Gas Chromatography with Microwave-Induced Helium Plasma Atomic Emission Spectroscopy

“…The atoms are excited to a higher electron excited state and specific frequencies of light as they transition to lower electron states. The strength of AED lies in the ability to simultaneously determine 23 different atomic emissions in analytes that are amenable to gas chromatography (GC), such as organometallics. − Therefore, a great deal of sample information can be achieved with a single analysis. AED is quite sensitive for mercury emission, with a reported detection limit in the range of 0.1 pg of Hg/s at either 185 or 254 nm and selectivity in the range of 10 000 …”